agetty | agetty [options] port baudrate [term] System administration command. The Linux version of getty. Set terminal type, modes, speed, and
line discipline. agetty is invoked
by init. It is the second process in
the series init-getty-login-shell,
which ultimately connects a user with the Linux system. agetty reads the user's login name and invokes
the login command with the user's
name as an argument. While reading the name, agetty attempts to adapt the system to the
speed and type of device being used.
You must specify a port, which agetty
will search for in the /dev directory. You may
use -, in which case agetty reads from standard input. You must also
specify baudrate, which may be a comma-separated
list of rates, through which agetty
will step. Optionally, you may specify the term,
which is used to override the TERM environment variable.
Options
- -h
Specify hardware, not software, flow control.
- -i
Suppress printing of /etc/issue before printing the
login prompt.
- -l program
Specify the use of program instead of /bin/login.
- -m
Attempt to guess the appropriate baud rate.
- -t timeout
Specify that agetty should exit if the open on
the line succeeds and there is no response to the login
prompt in timeout seconds.
- -L
Do not require carrier detect; operate locally only.
Use this when connecting terminals.
|
apmd |
apmd [options] System administration command. apmd
handles events reported by the Advanced Power Management BIOS
driver. The driver reports on battery level and requests to enter
sleep or suspend mode. apmd will log
any reports it gets via syslogd and
take steps to make sure that basic sleep and suspend requests are
handled gracefully. You can fine-tune the behavior of apmd by specifying an apmd_proxy command to run when it receives an
event.
Options
- -c n,
--check n
Set the number of seconds to wait for an event
before rechecking the power level. Default is to wait
indefinitely. Setting this causes the battery levels to be
checked more frequently.
- -P command, --apmd_prxy command
Specify the apmd_proxy command to run when APM driver events are reported. This is generally a shell script. The command will be invoked with parameters indicating what kind of event was received. The parameters are in the next list.
- -p n, --percentage n
Log information whenever the power changes by
n percent. The default is 5. Values greater than 100 will disable logging of power changes.
- -V, --version
Print version and exit.
- -v, --version
Verbose mode; all events are logged.
- -W, --wall
Use wall to alert all users of a low battery status.
- -w n, --warn n
Log a warning at ALERT level when the battery charge drops below n percent. The default is 10. Negative values disable low battery level warnings.
- -q, --quiet
Disable low battery level warnings.
- -?, --help
Print help summary and exit.
Parameters
The apmd proxy script will be invoked with the following parameters:
- start
Invoked when the daemon starts.
- stop
Invoked when the daemon stops.
- suspend [ system | user ]
Invoked when a suspend request has been made. The second parameter indicates whether the request was made by the system or by the user.
- standby [ system | user ]
Invoked when a standby request has been made. The second parameter indicates whether the request was made by the system or by the user.
- resume [ suspend | standby | critical ]
Invoked when the system resumes normal operation. The second
parameter indicates the mode the system was in before resuming.
(critical suspends indicate an emergency shutdown. After a
critical suspend the system may be unstable and you can use the resume
command to help you recover from the suspension.
- change power
Invoked when system power is changed from AC to battery or from battery to AC.
- change battery
Invoked when the APM BIOS driver reports that the battery is low.
- change capability
Invoked when the APM BIOS driver reports some hardware that affects its capability has been added or removed.
|
apropos | apropos string ... Search the short manual page descriptions in the whatis database for occurrences of each
string and display the result on the standard
output. Like whatis, except that it
searches for strings instead of words. Equivalent to man -k.
|
ar | ar [-V] key [args] [posname] archive [files] Maintain a group of files that are combined into
a file archive.
Used most commonly to create and update library files as used by the
link editor (ld). Only one key letter may be used, but each
can be combined with additional args (with no separations between).
posname is the name of a file in archive. When moving or
replacing files, you can specify that they be placed
before or after posname.
-V prints the version number of ar on standard error.
Key
- d
Delete files from archive.
- m
Move files to end of archive.
- p
Print files in archive.
- q
Append files to archive.
- r
Replace files in archive.
- t
List the contents of archive or list the named files.
- x
Extract contents from archive or only the named files.
Arguments
- a
Use with r or m key to place files
in the archive after posname.
- b
Same as a but before posname.
- c
Create archive silently.
- f
Truncate long filenames.
- i
Same as b.
- l
For backward compatibility; meaningless in Linux.
- o
Preserve original timestamps.
- s
Force regeneration of archive symbol table
(useful after running strip).
- S
Do not regenerate symbol table.
- u
Use with r to replace
only files that have changed since being put in archive.
- v
Verbose; print a description of actions taken.
Example
Replace mylib.a with object files from the current directory:
ar r mylib.a `ls *.o
|
arch | arch
Print machine architecture type to standard output. Equivalent
to uname -m.
|
arp | arp [options] TCP/IP command. Clear, add to, or dump the kernel's ARP
cache (/proc/net/arp).
Options
- -v
Verbose mode.
- -t type
Search for type entries when examining the ARP cache. type
must be ether (Ethernet)
or ax25 (AX.25 packet radio); ether is the default.
- -a [hosts]
Display hosts' entries or, if none are specified, all entries.
- -d host
Remove host's entry.
- -s host hardware-address
Add the entry host hardware-address, where
ether class addresses are 6 hexadecimal bytes, colon-separated.
- -f file
Read entries from file and add them.
|
as | as [options] files Generate an object file from each specified assembly language
source file. Object files have the same root name as
source files but replace the .s suffix with .o.
There may be some additional system-specific options.
Options
- -- [ | files]
Read input files from standard input, or from files if the pipe
is used.
- -a[dhlns][=file]
With only the -a option, list source code, assembler listing,
and symbol table.
The other options specify additional things to list or omit:
- -ad
Omit debugging directives.
- -ah
Include the high-level source code, if available.
- -al
Include an assembly listing.
- -an
Suppress forms processing.
- -as
Include a symbol listing.
- =file
Set the listing filename to file.
- -defsym symbol=value
Define the symbol to have the value value, which must be
an integer.
- -f
Skip preprocessing.
- --gstabs
Generate stabs debugging information.
- -o objfile
Place output in object file objfile (default is file.o).
- -v
Display the version number of the assembler.
- -I path
Include path when searching for .include directives.
- -K
Warn before altering difference tables.
- -L
Do not remove local symbols, which begin with L.
- -R
Combine both data and text in text section.
- -W
Quiet mode.
|
at | at [options] time Execute commands at a specified time and optional
date. The commands are read from standard input
or from a file. (See also batch.) End
input with EOF. time can be
formed either as a numeric hour (with optional minutes and modifiers)
or as a keyword. It can contain an optional date,
formed as a month and date, a day of the week, or a special keyword
(today or tomorrow). An
increment can also be specified.
The at command
can always be issued by a privileged user. Other
users must be listed in the file
/etc/at.allow if it exists; otherwise, they must
not be listed in /etc/at.deny. If neither file exists,
only a privileged user can issue the command.
Options
- -c job [job...]
Display the specified jobs on the standard output. This option does not take a
time specification.
- -d job [job...]
Delete the specified jobs. Same as atrm.
- -f file
Read job from file, not standard input.
- -l
Report all jobs that are scheduled for the invoking user.
Same as atq.
- -m
Mail user when job has completed,
regardless of whether output was created.
- -q letter
Place job in queue denoted by letter, where letter is any
single letter from a-z or A-Z. Default queue is a. (The batch
queue defaults to
b.) Higher-lettered queues run at a lower priority.
- -V
Display the version number.
Time
- hh:mm [modifiers]
Hours can have one digit or two (a 24-hour clock is assumed by default);
optional minutes can be given as one or two digits;
the colon can be omitted if the format is h, hh, or hhmm;
(e.g., valid times are 5, 5:30, 0530, 19:45).
If modifier am or pm is added, time is based on
a 12-hour clock. If the keyword zulu
is added, times correspond to Greenwich Mean Time.
- midnight | noon | teatime | now
Use any one of these keywords in place of a numeric time.
teatime translates to 4:00 p.m.;
now must be followed by an increment.
Date
- month num[, year]
month is one of the 12 months, spelled out or abbreviated to
its first three letters; num is the calendar date of the month;
year is the four-digit year. If the given month occurs before
the current month, at schedules that month next year.
- day
One of the seven days of the week, spelled out or abbreviated to its
first three letters.
- today | tomorrow
Indicate the current day or the next day. If date is omitted,
at schedules today when the specified time occurs
later than the current time; otherwise, at schedules tomorrow.
Increment
Supply a numeric increment if you want to specify an execution time or day
relative to the current time. The number should precede any of
the keywords minute, hour, day, week, month, or
year (or their plural forms). The keyword next can be used
as a synonym of + 1.
Examples
Note that the first two commands are equivalent:
at 1945 pm December 9
at 7:45pm Dec 9
at 3 am Saturday
at now + 5 hours
at noon next day
|
atq | atq [options] List the user's pending jobs, unless the user is
a privileged user; in that case, everybody's jobs are
listed. Same as at -l.
Options
- -q queue
Query only the specified queue and ignore all other queues.
- -v
Show jobs that have completed but not yet been deleted.
- -V
Print the version number.
|
atrm | atrm [options] job [job...] Delete jobs that have been queued for future execution.
Same as at -d.
Options
- -q queue
Remove job from the specified queue.
- -V
Print the version number and then exit.
|
badblocks | badblocks [options] device block-count System administration command.
Search device for bad blocks. You must specify the number of blocks
on the device (block-count).
Options
- -b blocksize
Expect blocksize-byte blocks.
- -o file
Direct output to file.
- -v
Verbose mode.
- -w
Test by writing to each block and then reading back from it.
|
banner | banner [option] [characters] Print characters as a poster.
If no characters are supplied, banner prompts for them and reads
an input line from standard input. By default, the results go to standard
output, but they are intended to be sent to a printer.
Option
- -w width
Set width to width characters. Note that if your
banner is in all lowercase, it will be narrower than width characters.
If -w is not specified, the default width is 132. If -w is
specified but width is not provided, the default is 80.
Example
/usr/games/banner -w50 Happy Birthday! |lpr
|
basename | basename name [suffix] basename option Remove leading directory components from a path. If
suffix is given, remove that also. The result is
printed to standard output.
Options
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
Examples
% basename /usr/lib/libm.a
libm.a
% basename /usr/lib/libm.a .a
libm
|
batch | batch [options] [time] Execute commands entered on standard input. If time is omitted,
execute them when the system load permits (when the load average
falls below 0.8). Very similar to at,
but does not insist that the execution time be entered on the command
line. See at for details.
Options
- -f file
Read job from file, not standard input.
- -m
Mail user when job has completed,
regardless of whether output was created.
- -q letter
Place job in queue denoted by letter,
where letter is one
letter from a-z or A-Z. The default queue is a. (The batch
queue defaults to b.) Higher-lettered queues run at a lower priority.
- -V
Print the version number and then exit.
- -v
Display the time a job will be executed.
|
bash | bash [options] [file [arguments;]] sh [options] [file [arguments]] Standard Linux shell, a command interpreter into which all
other commands are entered. For more information,
see Chapter 7, "bash: The Bourne-Again Shell".
|
bc | bc [options] [files] bc is a language (and compiler) whose syntax resembles that of C,
but with unlimited-precision arithmetic.
bc consists of identifiers, keywords, and symbols, which
are briefly described in the following entries. Examples are given at
the end.
Interactively perform arbitrary-precision arithmetic or convert numbers
from one base to another. Input can be taken from
files or read from the standard input. To exit, type
quit or EOF.
Options
- -l, --mathlib
Make functions from the math library available.
- -s, --standard
Ignore all extensions, and process exactly as in POSIX.
- -w, --warn
When extensions to POSIX bc are used, print a
warning.
- -q, --quiet
Do not display welcome message.
- -v, --version
Print version number.
Identifiers
An identifier is a series of one or more characters. It must begin
with a lowercase letter but may also contain digits and underscores.
No uppercase letters are allowed.
Identifiers are used as names for variables, arrays, and functions.
Variables normally store arbitrary-precision numbers.
Within the same program you may name a variable, an array,
and a function using the same letter. The following identifiers would
not conflict:
- x
Variable x.
- x[i]
Element i of array x. i can range from 0 to 2047
and can also be an expression.
- x(y,z)
Call function x with parameters y and z.
Input-output keywords
ibase, obase, scale, and last store a value.
Typing them on a line by themselves
displays their current value. You can also change
their values through assignment. The letters A-F are treated
as digits whose values are 10-15.
- ibase = n
Numbers that are input (e.g., typed) are read as base n (default is 10).
- obase = n
Numbers that are displayed are in base n (default is 10). Note: Once ibase has been changed from 10, use A
to restore ibase or obase to decimal.
- scale = n
Display computations using n decimal places (default is 0,
meaning that results are truncated to integers). scale is normally used only for base-10 computations.
- last
Value of last printed number.
Statement keywords
A semicolon or a newline separates one statement from another.
Curly braces are needed when grouping multiple statements.
- if
(rel-expr)
{statements} [else
{statements}]
Do one or more statements if relational expression
rel-expr is true. Otherwise, do nothing, or if else
(an extension)
is specified, do alternative statements. For example:
if(x==y) {i = i + 1} else {i = i - 1}
- while (rel-expr) {statements}
Repeat one or more statements while rel-expr is true; for
example:
while(i>0) {p = p*n; q = a/b; i = i-1}
- for (expr1;rel-expr;expr2) {statements}
Similar to while; for example, to print the first 10 multiples of
5, you could type:
for(i=1; i<=10; i++) i*5
GNU bf does not require three arguments to for.
A missing argument 1 or 3 means that those
expressions will never be evaluated. A missing argument
2 evaluates to the value 1.
- break
Terminate a while or for statement.
- print list
GNU extension. It provides an alternate means
of output. list consists of a series of comma-separated
strings and expressions; print displays these entities in the
order of the list. It does not print a newline when it terminates. Expressions are evaluated, printed, and assigned to the special
variable last. Strings (which may contain special characters,
i.e., characters beginning with \) are simply printed. Special
characters can be:
- a
Alert or bell
- b
Backspace
- f
Form feed
- n
Newline
- r
Carriage return
- q
Double quote
- t
Tab
- \
Backslash
- continue
GNU extension. When within a for statement, jump to the next iteration.
- halt
GNU extension. Cause the bc processor to quit.
- limits
GNU extension. Print the limits enforced by the local version of bc.
Function keywords
- define f(args) {
Begin the definition of function f having the arguments args. The arguments are separated by commas. Statements follow on successive lines. End with a }.
- auto x, y
Set up x and y as variables local to a function definition,
initialized to 0 and meaningless outside the function. Must appear first.
- return(expr)
Pass the value of expression expr back to the program.
Return 0 if (expr) is left off. Used in function
definitions.
- sqrt(expr)
Compute the square root of expression expr.
- length(expr)
Compute how many significant digits are in expr.
- scale(expr)
Same as length, but count only digits to the right of the decimal point.
- read( )
GNU extension. Read a number from standard input. Return value
is the number read, converted via the value of ibase.
Math library functions
These are available when bc is invoked with -l.
Library functions set scale to 20.
- s(angle)
Compute the sine of angle, a constant or expression
in radians.
- c(angle)
Compute the cosine of angle, a constant or expression
in radians.
- a(n)
Compute the arctangent of n, returning an angle in radians.
- e(expr)
Compute e to the power of expr.
- l(expr)
Compute the natural log of expr.
- j(n, x)
Compute the Bessel function of integer order n.
Operators
These consist of operators and other symbols.
Operators can be arithmetic, unary, assignment, or relational:
- arithmetic
+ - * / % ^
- unary
- ++ --
- assignment
=+ =- =* =/ =% =^ =
- relational
< <= > >= == !=
Other symbols
- /* */
Enclose comments.
- ()
Control the evaluation of expressions (change precedence). Can also be used around assignment statements to force the
result to print.
- {}
Use to group statements.
- []
Indicate array index.
- "text"
Use as a statement to print text.
Examples
Note in these examples that when you type some quantity (a number or expression),
it is evaluated and printed, but assignment statements produce no display.
ibase = 8 Octal input
20 Evaluate this octal number
16 Terminal displays decimal value
obase = 2 Display output in base 2 instead of base 10
20 Octal input
10000 Terminal now displays binary value
ibase = A Restore base-10 input
scale = 3 Truncate results to 3 decimal places
8/7 Evaluate a division
1.001001000 Oops! Forgot to reset output base to 10
obase=10 Input is decimal now, so A isn't needed
8/7
1.142 Terminal displays result (truncated)
The following lines show the use of functions:
define p(r,n){ Function p uses two arguments
auto v v is a local variable
v = r^n r raised to the n power
return(v)} Value returned
scale=5
x=p(2.5,2) x = 2.5 ^ 2
x Print value of x
6.25
length(x) Number of digits
3
scale(x) Number of places right of decimal point
2
|
biff | biff [arguments] Notify user of mail arrival and sender's name. biff
operates asynchronously. Mail notification works only if your
system is running the comsat(8) server. The command
biff y enables notification, and the command biff n
disables notification. With no arguments, biff
reports biff's current status.
|
bison | bison [options] file Given a file containing context-free grammar,
convert into tables for subsequent parsing
while sending output to file.c. This utility is both to a large
extent compatible with yacc and named for it. All input files
should use the suffix .y; output files will use the
original prefix. All long options (those preceded by --) may
instead be preceded by +.
Options
- -b prefix, --file-prefix=prefix
Use prefix for all output files.
- -d, --defines
Generate file.h, producing #define statements
that relate bison's token codes to the token names
declared by the user.
- -r, --raw
Use bison token numbers, not yacc-compatible translations,
in file.h.
- -k, --token-table
Include token names and values of YYNTOKENS, YYNNTS,
YYNRULES, and YYNSTATES in file.c.
- -l, --no-lines
Exclude #line constructs from code produced in file.c.
(Use after debugging is complete.)
- -n, --no-parser
Suppress parser code in output, allowing only declarations. Assemble all translations into a switch statement body and
print it to file.act.
- -o file, --output-file=file
Output to file.
- -p prefix, --name-prefix=prefix
Substitute prefix for yy in all external symbols.
- -t, --debug
Compile runtime debugging code.
- -v, --verbose
Verbose mode. Print diagnostics and notes about parsing tables to
file.output.
- -V, --version
Display version number.
- -y, --yacc, --fixed-output-files
Duplicate yacc's conventions for naming output files.
|
bootpd | bootpd [options] [configfile [dumpfile] ] TCP/IP command.
Internet Boot Protocol server. bootpd normally is run by
/etc/inetd by including the following line in the file
/etc/inetd.conf:
bootps dgram udp wait root /etc/bootpd bootpd
This causes bootpd to be started only when a boot request
arrives.
It may also be started in standalone mode, from the command line.
Upon startup, bootpd first reads its configuration
file, /etc/bootptab (or the configfile listed on the
command line), then begins listening for BOOTREQUEST packets.
bootpd looks in /etc/services to find the port numbers it
should use. Two entries are extracted: bootps -- the bootp server
listening port -- and bootpc -- the destination port used
to reply to clients.
If
bootpd is compiled with the -DDEBUG option, receipt of a SIGUSR1
signal causes it to dump its memory-resident database to the file
/etc/bootpd.dump or the command-line specified dumpfile.
Options
- -c directory
Force bootpd to work in directory.
- -d level
Specify the debugging level. Omitting level will increment
the level by 1.
- -t timeout
Specify a timeout value in minutes. A timeout value
of 0 means wait forever.
Configuration file
The bootpd configuration file has a format in which two-character, case-sensitive
tag symbols are used to represent host parameters. These parameter
declarations are separated by colons. The general format is:
hostname:tg=value:tg=value:tg=value
where hostname is the name of a bootp client and tg
is a tag symbol. The currently recognized tags are listed next.
Tags
Tag |
Meaning |
bf |
Bootfile |
bs |
Bootfile size in 512-octet blocks |
cs |
Cookie server address list |
ds |
Domain name server address list |
gw |
Gateway address list |
ha |
Host hardware address |
hd |
Bootfile home directory |
hn |
Send hostname |
ht |
Host hardware type (see Assigned Numbers RFC) |
im |
Impress server address list |
ip |
Host IP address |
lg |
Log server address list |
lp |
lpr server address list |
ns |
IEN-116 name server address list |
rl |
Resource location protocol server address list |
sm |
Host subnet mask |
tc |
Table continuation |
to |
Time offset in seconds from UTC |
ts |
Time server address list |
vm |
Vendor magic cookie selector |
There is also a generic tag, Tn, where n is an RFC 1048
vendor field tag number. Generic data may be represented as either a
stream of hexadecimal numbers or as a quoted string of ASCII
characters.
|
bootpgw | bootpgw [options] server Internet Boot Protocol Gateway.
Maintain a gateway that forwards bootpd requests to server.
In addition to dealing with BOOTREPLY packets, also deal with
BOOTREQUEST packets. bootpgw is normally run by
/etc/inetd by including the following line in the file
/etc/inetd.conf:
bootps dgram udp wait root /etc/bootpgw bootpgw
This causes bootpgw to be started only when a boot request
arrives. bootpgw takes all the same options as bootpd,
except -c.
|
bootptest | bootptest [options] server [template] TCP/IP command. Test server's bootpd daemon by sending
requests every second for 10 seconds or until the server responds.
Read options from the template file, if provided.
Options
- -f file
Read the boot filename from file.
- -h
Identify client by hardware, not IP, address.
- -m magic-number
Provide magic-number as the first word of the vendor options
field.
|
bzip2 | bzip2 [options] filenames bunzip2 [options] filenames bzcat [option] filenames bzip2recover filenames File compression and decompression utility similar to
gzip, but uses a different algorithm and encoding
method to get better compression. bzip2 replaces
each file in filenames with a compressed version
of the file and with a .bz2 extension appended.
bunzip2 decompresses each file compressed by
bzip2 (ignoring other files, except to print a
warning).
bzcat decompresses all specified files
to standard output, and bzip2recover is used to try
to recover data from damaged files.
Options
- --
End of options; treat all subsequent arguments as filenames.
- -dig
Set block size to dig × 100KB when compressing, where
dig is a single digit from 1 to 9.
- -c, --stdout
Compress or decompress to standard output.
- -d, --decompress
Force decompression.
- -f, --force
Force overwrite of output files. Default is not to overwrite. Also forces
breaking of hard links to files.
- -k, --keep
Keep input files; don't delete them.
- -L, --license, -V, --version
Print license and version information and exit.
- -q, --quiet
Quiet. Print only critical messages.
- -s, --small
Use less memory, at the expense of speed.
- -t, --test
Check the integrity of the files, but don't actually compress them.
- -v, --verbose
Verbose. Show the compression ratio for each file processed. Add more
-v's to increase the verbosity.
- -z, --compress
Forces compression, even if invoked as bunzip2 or
bzcat.
- --repetitive-fast, --repetitive-best
Sometimes useful in versions earlier than 0.9.5 (which has an improved
sorting algorithm) for providing some control over the algorithm.
|
c++ | c++ [options] files See g++.
|
cal | cal [-jy] [[month] year] Print a 12-month calendar (beginning with January)
for the given year or a one-month calendar of the given
month and year. month ranges from 1 to 12.
year ranges from 1 to 9999.
With no arguments, print a calendar for the
current month.
Options
- -j
Display Julian dates (days numbered 1 to 365, starting
from January 1).
- -m
Display Monday as the first day of the week.
- -y
Display entire year.
Examples
cal 12 1995
cal 1994 > year_file
|
cardctl |
cardctl [options] command System administration command. Control PCMCIA sockets or select the
current scheme. The current scheme is sent along with the address of
any inserted cards to configuration scripts (by default located in
/etc/pcmcia). The scheme command displays or changes the scheme.
The other commands operate on a named card socket number or, if no
number is given, all sockets.
Commands
- config [socket]
Display current socket configuration.
- eject [socket]
Prepare the system for the card(s) to be ejected.
- ident [socket]
Display card identification information.
- insert [socket]
Notify system that a card has been inserted.
- reset [socket]
Send reset signal to card.
- resume [socket]
Restore power to socket and reconfigure for use.
- scheme [name]
Display current scheme or change to specified scheme
name.
- status [socket]
Display current socket status.
- suspend [socket]
Shut down device and cut power to socket.
Options
- -c directory
Look for card configuration information in directory instead
of /etc/pcmcia.
- -f file
Use file to keep track of the current scheme
instead of /var/run/pcmcia-scheme.
- -s file
Look for current socket information in file instead
of /var/run/stab.
|
cardmgr |
cardmgr [options] System administration command. The PCMCIA card daemon. cardmgr monitors PCMCIA sockets for devices
that have been added or removed. When a card is detected, it attempts
to get the card's ID and configure it according to the card
configuration database (usually stored in
/etc/pcmcia/config). By default, cardmgr both creates a system log entry when it
detects cards and beeps. Two high beeps mean it successfully identified
and configured a device. One high beep followed by one low beep means
it identified the device, but was unable to configure it successfully. One low
beep means it could not identify the inserted card.
Information on the currently configured cards can be found in
/var/run/stab.
Options
- -cdirectory
Look in directory for the
card configuration database instead of /etc/pcmcia.
- -d
use modprobe
instead of insmod to load the
PCMCIA device driver.
- -f
Run in the foreground to process
the current cards, then run as a daemon.
- -mdirectory
Look in directory for card
device modules instead of /lib/modules/
`uname -r`.
- -o
Configure the cards present in one pass, then exit.
- -pfile
Write cardmgr's
process ID to file instead of
/var/run/cardmgr.pid.
- -q
Run in quiet mode. No beeps.
- -sfile
Write current socket information to
file instead of
/var/run/stab.
- -v
Verbose mode.
- -V
Print version number and exit.
|
cat | cat [options] [files] Read (concatenates)
one or more files and print them on standard output.
Read standard input if no files are specified or if - is specified
as one of the files; input ends with EOF.
You can use the > operator to combine several files into
a new file or >> to append files to an existing file.
Options
- -A, --show-all
Same as -vET.
- -b, --number-nonblank
Number all nonblank output lines, starting with 1.
- -e
Same as -vE.
- -E, --show-ends
Print $ at the end of each line.
- -n, --number
Number all output lines, starting with 1.
- -s, --squeeze-blank
Squeeze down multiple blank lines to one blank line.
- -t
Same as -vT.
- -T, --show-tabs
Print TAB characters as ^I.
- -u
Ignored; retained for Unix compatibility.
- -v, --show-nonprinting
Display control and nonprinting characters, with the exception
of LINEFEED and TAB.
Examples
cat ch1 Display a file
cat ch1 ch2 ch3 > all Combine files
cat note5 >> notes Append to a file
cat > temp1 Create file at terminal; end with EOF
cat > temp2 << STOP Create file at terminal; end with STOP
|
cc | cc [options] files See gcc.
|
cpp | cpp [options] [ ifile [ ofile ] ] GNU C language preprocessor. cpp is invoked as the first pass
of any C compilation by the gcc command. The output of cpp
is a form acceptable as input to the next pass of the C compiler, and
cpp normally invokes gcc after it finishes processing.
ifile and ofile are, respectively, the input and output for
the preprocessor; they default to standard input and standard output.
Options
- -$
Do not allow $ in identifiers.
- -dM
Suppress normal output. Print series of #defines that create
the macros used in the source file.
- -dD
Similar to -dM but exclude predefined macros and include
results of preprocessing.
- -idirafter dir
Search dir for header files when a header file is not found in
any of the included directories.
- -imacros file
Process macros in file before processing main files.
- -include file
Process file before main file.
- -iprefix prefix
When adding directories with -iwithprefix, prepend
prefix to the directory's name.
- -iwithprefix dir
Append dir to the list of directories to be searched when
a header file cannot be found in the main include path.
If -iprefix has been set, prepend that prefix to the
directory's name.
- -lang-c, -lang-c++, -lang-objc, -lang-objc++
Expect the source to be in C, C++,
Objective C, or Objective C++, respectively.
- -lint
Display all lint commands in comments as #pragma lint command.
- -nostdinc
Search only specified, not standard, directories for header files.
- -nostdinc++
Suppress searching of directories believed to contain C++-specific
header files.
- -pedantic
Warn verbosely.
- -pedantic-errors
Produce a fatal error in every case in which -pedantic would have produced
a warning.
- -traditional
Behave like traditional C, not ANSI.
- -undef
Suppress definition of all nonstandard macros.
- -Aname[=def]
Assert name with value def as if defined by a #assert.
- -C
Pass along all comments (except those found on cpp directive
lines). By default, cpp strips C-style comments.
- -Dname[=def]
Define name with value def as if by a #define. If no
=def is given, name is defined with value 1. -D has
lower precedence than -U.
- -H
Print pathnames of included files, one per line, on standard error.
- -Idir
Search in directory dir for #include files whose names do not begin
with / before looking in directories on standard list.
#include files whose names are enclosed in double quotes and do
not begin with / will be searched for first in the current directory,
then in directories named on -I options, and last in directories
on the standard list.
- -M [-MG]
Suppress normal output. Print a rule for make that describes the main source file's
dependencies. If -MG is specified, assume that missing header files are actually
generated files, and look for them in the source file's directory.
- -MD file
Similar to -M, but output to file; also compile
the source.
- -MM
Similar to -M. Describe only those files included as a result
of #include "file".
- -MMD file
Similar to -MD, but describe only the user's header files.
- -P
Preprocess input without producing line-control information used by
next pass of C compiler.
- -Uname
Remove any initial definition of name, where name is a
reserved symbol predefined by the preprocessor or a name defined on a
-D option. Names predefined by cpp are unix and
i386 (for Intel systems).
- -Wcomment, -Wcomments
Warn when encountering the beginning of a nested comment.
- -Wtraditional
Warn when encountering constructs that are interpreted differently
in ANSI from traditional C.
Special names
cpp understands various special names, some of which are:
- __DATE__
Current date (e.g., Oct 10 1999)
- __FILE__
Current filename (as a C string)
- __LINE__
Current source line number (as a decimal integer)
- __TIME__
Current time (e.g., 12:00:00)
These special names can be used anywhere, including macros, just
like any other defined names. cpp's understanding of the line
number and filename may be changed using a #line directive.
Directives
All cpp directive lines start with # in column 1. Any number of
blanks and tabs is allowed between the # and the directive. The
directives are:
- #assert name (string)
Define a question called name, with an answer of
string. Assertions can be tested with #if
directives. The predefined assertions for #system, #cpu, and
#machine can be used for architecture-dependent changes.
- #unassert name
Remove assertion for question name.
- #define name token-string
Define a macro called name, with a value of token-string.
Subsequent instances of name are replaced with token-string.
- #define name( arg, ... , arg ) token-string
This allows substitution of a macro with arguments.
token-string will be substituted for name in the input
file. Each call to name in the source file includes arguments
that are plugged into the corresponding args in token-string.
- #undef name
Remove definition of the macro name. No additional tokens are
permitted on the directive line after name.
- #ident string
Put string into the comment section of an object file.
- #include "filename", #include<filename>
Include contents of filename at this point in the program. No
additional tokens are permitted on the directive line after the final "
or >.
- #line integer-constant "filename"
Cause cpp to generate line-control information for the next pass of
the C compiler. The compiler behaves as if integer-constant is the
line number of the next line of source code and filename (if
present) is the name of the input file. No additional tokens are
permitted on the directive line after the optional filename.
- #endif
End a section of lines begun by a test directive (#if, #ifdef, or
#ifndef). No additional tokens are permitted on the directive line.
- #ifdef name
Lines following this directive and up to matching #endif or next
#else or #elif will appear in the output if name is
currently defined. No additional tokens are permitted on the directive
line after name.
- #ifndef name
Lines following this directive and up to matching #endif or next
#else or #elif will appear in the output if name is not
currently defined. No additional tokens are permitted on the directive
line after name.
- #if constant-expression
Lines following this directive and up to matching #endif or next
#else or #elif will appear in the output if
constant-expression evaluates to nonzero.
- #elif constant-expression
An arbitrary number of #elif directives are allowed between an
#if, #ifdef, or #ifndef directive and an #else
or #endif directive. The lines following the #elif and up
to the next #else, #elif, or #endif directive will
appear in the output if the preceding test directive
and all intervening #elif directives evaluate to zero, and the
constant-expression evaluates to nonzero. If
constant-expression evaluates to
nonzero, all succeeding #elif and #else directives will be ignored.
- #else
Lines following this directive and up to the matching #endif will
appear in the output if the preceding test directive evaluates to 0,
and all intervening #elif directives evaluate to 0. No
additional tokens are permitted on the directive line.
- #error
Report fatal errors.
- #warning
Report warnings, but then continue processing.
|
cfdisk | cfdisk [options] [device] System administration command.
Partition a hard disk. device may be /dev/hda (default),
/dev/hdb, /dev/sda, /dev/sdb, /dev/sdc,
or /dev/sdd. See also fdisk.
Options
- -a
Highlight the current partition with a cursor, not reverse video.
- -c cylinders
Specify the number of cylinders.
- -h heads
Specify the number of heads.
- -s sectors
Specify the number of sectors per track.
- -z
Do not read the partition table; partition from scratch.
- -P format
Display the partition table in format, which must be
r (raw data), s (sector order), or t (raw format).
Commands
- up arrow, down arrow
Move among partitions.
- b
Toggle partition's bootable flag.
- d
Delete partition (allow other partitions to use its space).
- g
Alter the disk's geometry. Prompt for what to change:
cylinders, heads, or sectors (c, h, or s,
respectively).
- h
Help.
- m
Attempt to ensure maximum usage of disk space in the partition.
- n
Create a new partition. Prompt for more information.
- p
Display the partition table.
- q
Quit without saving information.
- t
Prompt for a new filesystem type, and change to that type.
- u
Change the partition size units, rotating from megabytes to
sectors to cylinders and back.
- W
Save information. Note that this letter must be uppercase.
|
chattr | chattr [options] mode files Modify file attributes. Specific to Linux Second Extended Filesystem. Behaves similarly to symbolic chmod,
using +, -, and =.
mode is in the form opcode attribute.
See also lsattr.
Options
- -R
Modify directories and their contents recursively.
- -V
Print modes of attributes after changing them.
- -v version
Set the file's version.
Opcodes
- +
Add attribute.
- -
Remove attribute.
- =
Assign attributes (removing unspecified attributes).
Attributes
- A
Don't update access time on modify.
- a
Append only for writing. Can be set or
cleared only by a privileged user.
- c
Compressed.
- d
No dump.
- i
Immutable. Can be set or cleared only
by a privileged user.
- s
Secure deletion; the contents are zeroed on deletion.
- u
Undeletable.
- S
Synchronous updates.
Examples
chattr +a myfile As superuser
|
chfn | chfn [options] [username] Change the information that is stored in
/etc/passwd and
displayed when a user is fingered. Without options,
chfn
enters interactive mode and prompts for changes. To make a field
blank, enter the keyword none. Only a
privileged user can change information for another user. For regular users,
chfn prompts for the user's password before making
the change.
Options
- -f, --full-name
Specify new full name.
- -h, --home-phone
Specify new home phone number.
- -o, --office
Specify new office number.
- -p, --office-phone
Specify new office phone number.
- -u, --help
Print help message and then exit.
- -v, --version
Print version information and then exit.
Example
chfn -f "Ellen Siever" ellen
|
chgrp | chgrp [options] newgroup files chgrp [options] Change the group of one or more files to
newgroup. newgroup is
either a group ID number or a group name located in
/etc/group. Only the owner of a file or a
privileged user may change its group.
Options
- -c, --changes
Print information about those files that are changed.
- -f, --silent, --quiet
Do not print error messages about files that cannot be changed.
- --help
Print help message and then exit.
- -R, --recursive
Traverse subdirectories recursively, applying changes.
- --reference=filename
Change the group to that associated with filename.
In this case, newgroup is not specified.
- -v, --verbose
Verbosely describe ownership changes.
- --version
Print version information and then exit.
|
chmod | chmod [options] mode files chmod [options] --reference=filename files Change the access mode (permissions) of one or more files.
Only the owner of a file or a privileged user may change its mode.
mode can be numeric or an expression in the form of
who opcode permission.
who is optional (if omitted, default is a); choose only one opcode.
Multiple modes may be specified, separated by commas.
Options
- -c, --changes
Print information about files that are changed.
- -f, --silent, --quiet
Do not notify user of files that chmod cannot change.
- --help
Print help message and then exit.
- -R, --recursive
Traverse subdirectories recursively, applying changes.
- --reference=filename
Change permissions to those associated with
filename.
- -v, --verbose
Print information about each file, whether changed or not.
- --version
Print version information and then exit.
Who
- u
User
- g
Group
- o
Other
- a
All (default)
Opcode
- +
Add permission.
- -
Remove permission.
- =
Assign permission (and remove permission of the unspecified fields).
Permissions
- r
Read.
- w
Write.
- x
Execute.
- s
Set user (or group) ID.
- t
Sticky bit; save text (file) mode or prevent removal of files by nonowners
(directory).
- u
User's present permission.
- g
Group's present permission.
- o
Other's present permission.
Alternatively, specify permissions by a three-digit octal number. The first
digit designates owner permission; the second, group permission; and the
third,
other's permission. Permissions are calculated by adding
the following octal values:
- 4
Read.
- 2
Write.
- 1
Execute.
Note: A fourth digit may precede this sequence.
This digit assigns the following modes:
- 4
Set user ID on execution to grant permissions
to process based on file's owner, not on permissions of user
who created the process.
- 2
Set group ID on execution to grant permissions to process based on
the file's group, not on permissions of user who created the process.
- 1
Set sticky bit.
Examples
Add execute-by-user permission to file:
chmod u+x file
Either of the following will assign read/write/execute permission by owner (7),
read/execute permission by group (5), and execute-only permission
by others (1) to file:
chmod 751 file
chmod u=rwx,g=rx,o=x file
Any one of the following will assign read-only permission to file for everyone:
chmod =r file
chmod 444 file
chmod a-wx,a+r file
Set the user ID, assign
read/write/execute permission by owner, and assign read/execute
permission by group and others:
chmod 4755 file
|
chown | chown [options] newowner files chown [options] --reference=filename files Change the ownership of one or more
files to newowner.
newowner is either a user ID number or a login
name located in /etc/passwd. chown also accepts users in the form
newowner:newgroup or
newowner.newgroup. The last two forms change the
group ownership as well. If no owner is specified, the owner is
unchanged. With a period or colon but no group, the group is changed
to that of the new owner. Only the current owner of a file or a
privileged user may change its owner.
Options
- -c, --changes
Print information about those files that are changed.
- --dereference
Follow symbolic links.
- -f, --silent, --quiet
Do not print error messages about files that cannot be changed.
- -h, --no-dereference
Change the ownership of each symbolic link (on systems that allow it),
rather than the referenced file.
- -v, --verbose
Print information about all files that chown
attempts to change, whether or not they are actually changed.
- -R, --recursive
Traverse subdirectories recursively, applying changes.
- --reference=filename
Change owner to the owner of filename instead
of specifying a new owner explicitly.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
|
chpasswd | chpasswd [option] System administration command.
Change user passwords in a batch. chpasswd accepts input in the
form of one username:password pair per line. If the
-e option is not specified, password will be encrypted before
being stored.
Option
- -e
Passwords given are already encrypted.
|
chroot | chroot newroot [command] System administration command.
Change root directory for command or, if none is specified,
for a new copy of the user's shell. This command or shell
is executed relative to the new root. The meaning of any initial /
in pathnames is changed to newroot for a command and any of its
children. In addition, the initial working directory
is newroot. This command is restricted to privileged users.
|
chsh | chsh [options] [username] Change your login shell, interactively or on the command line.
Warn if shell does not exist in
/etc/shells. Specify the full path to the
shell. chsh prompts for your password. Only a
privileged user can change another user's shell.
Options
- -l, --list-shells
Print valid shells, as listed in /etc/shells, and then exit.
- -s shell, --shell shell
Specify new login shell.
- -u, --help
Print help message and then exit.
- -v, --version
Print version information and then exit.
Example
chsh -s /bin/tcsh
|
cksum | cksum [files] Compute a cyclic redundancy check (CRC) checksum for all
files; used to ensure that a file was not
corrupted during transfer.
Read from standard input if the character - or no files
are given. Display the resulting checksum, the number of
bytes
in the file, and (unless reading from standard input) the filename.
|
clear | clear Clear the terminal display.
|
cmp | cmp [options] file1 file2 [skip1 [skip2]] Compare file1 with file2. Use standard input if
file1 is - or
missing. See also comm and
diff. Files can be of any
type. skip1 and skip2 are optional
offsets in the files at which the comparison is to start.
Options
- -c, --print-chars
Print differing bytes as characters.
- -i num, --ignore-initial=num
Ignore the first num bytes of input.
- -l, --verbose
Print offsets and codes of all differing bytes.
- -s, --quiet, --silent
Work silently; print nothing, but return exit codes:
- 0
Files are identical.
- 1
Files are different.
- 2
Files are inaccessible.
Example
Print a message if two files are the same (exit code is 0):
cmp -s old new && echo 'no changes'
|
col | col [options] A postprocessing filter that handles reverse linefeeds and escape characters,
allowing output from tbl or nroff to
appear in reasonable form on a terminal.
Options
- -b
Ignore backspace characters; helpful when printing manpages.
- -f
Process half-line vertical motions, but not reverse line motion. (Normally, half-line input motion is displayed on the next full line.)
- -l n
Buffer at least n lines in memory. The default buffer
size is 128 lines.
- -x
Normally, col saves printing time by
converting sequences of spaces to tabs. Use
-x to suppress this conversion.
Examples
Run myfile through tbl and
nroff, then capture
output on screen by filtering through col
and more:
tbl myfile | nroff | col | more
Save manpage output for the ls command
in out.print,
stripping out backspaces (which would otherwise appear as ^H):
man ls | col -b > out.print
|
colcrt | colcrt [options] [files] A postprocessing filter that handles reverse linefeeds and escape characters,
allowing output from tbl or
nroff to appear in reasonable
form on a terminal. Put half-line characters (e.g., subscripts or
superscripts) and underlining (changed to dashes) on a new line between
output lines.
Options
- -
Do not underline.
- -2
Double space by printing all half-lines.
|
colrm | colrm [start [stop]] Remove specified columns from a file, where a column is a single character
in a line. Read from standard input and write to standard output.
Columns are numbered starting with 1; begin deleting columns
at (including) the start column, and stop at (including) the
stop column. Entering a tab increments the column count to the
next multiple of either the start or stop column;
entering a backspace decrements it by 1.
Example
colrm 3 5 < test1 > test2
|
column | column [options] [files] Format input from one or more files into columns,
filling rows first. Read from standard input if no files are
specified.
Options
- -c num
Format output into num columns.
- -s char
Delimit table columns with char. Meaningful only with -t.
- -t
Format input into a table. Delimit with whitespace, unless
an alternate delimiter has been provided with -s.
- -x
Fill columns before filling rows.
|
comm | comm [options] file1 file2 Compare lines common to the sorted files file1
and file2. Three-column output is produced:
lines unique to file1, lines unique to
file2, and lines common to both files. comm is similar to diff in that both commands compare two
files. But comm can also be used like
uniq; that is, comm selects duplicate or unique lines between
two sorted files, whereas uniq selects duplicate or unique lines within
the same sorted file.
Options
- -
Read the standard input.
- -num
Suppress printing of column num. Multiple columns
may be specified and should not be space-separated.
- --help
Print help message and exit.
- --version
Print version information and exit.
Example
Compare two lists of top-10 movies, and display items that appear
in both lists:
comm -12 siskel_top10 ebert_top10
|
compress | compress [options] files Compress one or more files, replacing each with the
compressed file of the same name with .Z appended. If
no file is specified, compress standard input. Each file specified is
compressed separately. compress ignores
files that are symbolic links. See also gzip.
Options
- -b maxbits
Limit the maximum number of bits.
- -c
Write output to standard output, not to a .Z
file.
- -d
Decompress instead of compressing. Same as
uncompress.
- -f
Force generation of an output file even if one already exists.
- -r
If any of the specified files is a directory, compress recursively.
- -v
Print compression statistics.
- -V
Print version and compilation information and then exit.
|
cp | cp [options] file1 file2 cp [options] files directory Copy file1 to file2, or copy one or more files
to the same names under directory.
If the destination is an existing file, the file is overwritten;
if the destination is an existing directory, the file is copied
into the directory (the directory is not overwritten).
Options
- -a, --archive
Preserve attributes of original files where possible.
Same as -dpR.
- -b, --backup
Back up files that would otherwise be overwritten.
- -d, --no-dereference
Do not dereference symbolic links; preserve hard
link relationships between source and copy.
- -f, --force
Remove existing files in the destination.
- -i, --interactive
Prompt before overwriting destination files.
- -l, --link
Make hard links, not copies, of nondirectories.
- -p, --preserve
Preserve all information, including owner, group, permissions,
and timestamps.
- -P, --parents
Preserve intermediate directories in source. The last argument must be the name of an existing directory.
For example, the command:
cp --parents jphekman/book/ch1 newdir
copies the file jphekman/book/ch1 to the file
newdir/jphekman/book/ch1,
creating intermediate directories as necessary.
- -r, -R, --recursive
Copy directories recursively.
- -S backup-suffix, --suffix=backup-suffix
Set suffix to be appended to backup files. This may also be set with the SIMPLE_BACKUP_SUFFIX
environment variable. The default is ~.
You need to explicitly include a period if you want one before the
suffix (e.g., specify .bak, not bak).
- -s, --symbolic-link
Make symbolic links instead of copying. Source filenames must
be absolute.
- -u, --update
Do not copy a file to an existing destination with the same or newer
modification time.
- -v, --verbose
Before copying, print the name of each file.
- -V type, --version-control=type
Set the type of backups made. You may also use the
VERSION_CONTROL environment variable. The default is
existing. Valid arguments are:
- t, numbered
Always make numbered backups.
- nil, existing
Make numbered backups of files that already
have them; otherwise, make simple backups.
- never, simple
Always make simple backups.
- -x, --one-file-system
Ignore subdirectories on other filesystems.
|
cpio | cpio flags [options] Copy file archives in from or out to tape or disk, or to another
location on the local machine.
Each of the three flags -i, -o, or -p
accepts different options.
Flags
- -i, --extract [options] [patterns]
Copy in (extract) from an archive files whose names match selected
patterns.
Each pattern can include Bourne shell filename metacharacters.
(Patterns should be quoted or escaped so they are interpreted by
cpio, not by the shell.) If pattern is
omitted, all files are copied in. Existing files are not overwritten
by older versions from the archive unless
-u is specified.
- -o, --create [options]
Copy out to an archive a list of files whose names are given on the
standard input.
- -p, --pass-through [options] directory
Copy (pass) files to another directory on the same system. Destination
pathnames are interpreted relative to the named directory.
Comparison of valid options
Options available to the -i, -o, and -p flags
are shown here.
(The - is omitted for clarity):
i: bcdf mnrtsuv B SVCEHMR IF
o: 0a c vABL VC HM O F
p: 0a d lm uv L V R
Options
- -0, --null
Expect list of filenames to be terminated with null,
not newline. This allows files with a newline in their names
to be included.
- -a, --reset-access-time
Reset access times of input files after reading them.
- -A, --append
Append files to an existing archive,
which must be a disk file. Specify this archive with -O or -F.
- -b, --swap
Swap bytes and half-words to convert between big-endian and
little-endian 32-bit integers.
- -B
Block input or output using 5120 bytes per record (default is 512 bytes
per record).
- --blocksize=size
Set input or output blocksize to size × 512
bytes.
- -c
Read or write header information as ASCII characters;
useful when source and destination machines are different types.
- -C n, --io-size=n
Like -B, but blocksize
can be any positive integer n.
- -d, --make-directories
Create directories as needed.
- -E file, --pattern-file=file
Extract filenames from the archives that match patterns in
file.
- -f, --nonmatching
Reverse the sense of copying; copy all files except
those that match patterns.
- -F file, --file=file
Use file as the archive, not
stdin or
stdout.
file can reside on another machine, if given in the form
user@hostname:file
(where user@ is optional).
- --force-local
Assume that file (provided by
-F,
-I, or
-O) is a local file, even if
it contains a colon (:) indicating a remote file.
- -H type, --format=type
Use type format. Default for copy-out is
bin; for copy-in the default is
autodetection of the format. Valid formats (all caps also accepted) are:
- bin
Binary
- odc
Old (POSIX.1) portable format
- newc
New (SVR4) portable format
- crc
New (SVR4) portable format with checksum added
- tar
Tar
- ustar
POSIX.1 tar (also recognizes GNU tar archives)
- hpbin
HP-UX's binary (obsolete)
- hpodc
HP-UX's portable format
- -I file
Read file as an input archive. May be on a remote machine
(see -F).
- -k
Ignored. For backward compatibility.
- -l, --link
Link files instead of copying.
- -L, --dereference
Follow symbolic links.
- -m, --preserve-modification-time
Retain previous file modification time.
- -M msg, --message=msg
Print msg when switching media, as a prompt before
switching to new media.
Use variable %d in the message as a numeric ID for the next medium.
-M is valid only with -I or -O.
- -n, --numeric-uid-gid
When verbosely listing contents, show user ID and group ID numerically.
- --no-absolute-filenames
Create all copied-in files relative to the current directory.
- --no-preserve-owner
Make all copied files owned by yourself, instead of the owner of the original.
Useful only if you are a privileged user.
- -O file
Archive the output to file, which may
be a file on another machine (see -F).
- --only-verify-crc
For a CRC-format archive, verify the CRC of each file; don't actually
copy the files in.
- --quiet
Don't print the number of blocks copied.
- -r
Rename files interactively.
- -R [user][:group], --owner [user][:group]
Reassign file ownership and group information to the user's login ID
(privileged users only).
- -s, --swap-bytes
Swap bytes of each two-byte half-word.
- -S, --swap-half-words
Swap half-words of each four-byte word.
- --sparse
For copy-out and copy-pass, write files that have large
blocks of zeros as sparse files.
- -t, --list
Print a table of contents of the input (create no files).
When used with the -v option,
resembles output of ls -l.
- -u, --unconditional
Unconditional copy; old files can overwrite new ones.
- -v, --verbose
Print a list of filenames processed.
- -V, --dot
Print a dot for each file read or written (this shows
cpio at work without cluttering the screen).
- --version
Print version number and then exit.
Examples
Generate a list of files whose names end in .old using find; use list
as input to cpio:
find . -name "*.old" -print | cpio -ocBv > /dev/rst8
Restore from a tape drive all files whose names contain save (subdirectories
are created if needed):
cpio -icdv "*save*" < /dev/rst8
Move a directory tree:
find . -depth -print | cpio -padm /mydir
|
cron | cron System administration command.
Normally started in a system startup file.
Execute commands at scheduled times, as specified in
users' files in /var/cron/tabs. Each file shares
its name with the user who owns it. The files are controlled
via the command crontab.
|
crontab | crontab [options] [file] View, install, or uninstall your current crontab file.
A privileged user can run crontab for another user by
supplying -u user.
A crontab file is a list of commands, one per line, that will execute
automatically at a given time. Numbers are supplied before each command
to specify the execution time. The numbers appear in five fields,
as follows:
Minute 0-59
Hour 0-23
Day of month 1-31
Month 1-12
Jan, Feb, Mar, ...
Day of week 0-6, with 0 = Sunday
Sun, Mon, Tue, ...
Use a comma between multiple values, a hyphen to indicate a range, and an
asterisk to indicate all possible values. For example, assuming these crontab
entries:
59 3 * * 5 find / -print | backup_program
0 0 1,15 * * echo "Timesheets due" | mail user
The first command backs up the system files every Friday at 3:59 a.m.,
and the second command mails a reminder on the 1st and 15th of each month.
The superuser can always issue the crontab command. Other
users must be listed in the file /etc/cron.allow if it
exists; otherwise, they must not be listed in /etc/cron.deny.
If neither file exists, only the superuser can issue the
command.
Options
The -e, -l, and -r
options are not valid if any files are
specified.
- -e
Edit the user's current crontab file (or create one).
- -l
Display the user's crontab file on standard output.
- -r
Delete the user's crontab file.
- -u user
Indicates which user's
crontab file will be acted upon.
|
csh | csh [options] [file [arguments]] C shell, a command interpreter into which all
other commands are entered. For more information,
see Chapter 8, "csh and tcsh".
|
csplit | csplit [options] file arguments Separate file into context-based sections
and place sections in files named xx00 through
xxn (n < 100),
breaking file at each pattern specified
in arguments. See also
split.
Options
- -
Read from standard input.
- -b suffix, --suffix-format=suffix
Append suffix to output filename. This option causes -n to be ignored. suffix must
specify how to convert the binary integer to readable form
by including exactly one of the following:
%d, %i, %u, %o, %x, or %X. The value of suffix determines the format
for numbers as follows:
- %d
Signed decimal
- %i
Same as %d
- %u
Unsigned decimal
- %o
Octal
- %x
Hexadecimal
- %X
Same as %x.
- -f prefix, --prefix=prefix
Name new files prefix00 through
prefixn (default is xx00 through xxn).
- -k, --keep-files
Keep newly created files, even when an error occurs (which would
normally remove these files).
This is useful when you need to specify an arbitrarily large repeat
argument, {n}, and you don't want an out-of-range error to cause removal of the new files.
- -n num, --digits=num
Use output filenames with numbers
num digits long. The default is 2.
- -s, -q, --silent, --quiet
Suppress all character counts.
- -z, --elide-empty-files
Do not create empty output files. However, number
as if those files had been created.
Arguments
Any one or a combination of the following expressions may be specified as arguments.
Arguments containing blanks or other special characters should be
surrounded by single quotes.
- /expr/[offset]
Create file from the current line up to the line
containing the regular expression expr. offset should be of the form +n or -n,
where n is the number of lines below or above expr.
- %expr%[offset]
Same as /expr/ except no file is created
for lines previous to line containing expr.
- num
Create file from current line up to (but not including)
line number num. When followed by a repeat count (number inside {}), put the
next num lines of input into another
output file.
- {n}
Repeat argument n times. May follow any of the preceding arguments.
Files will split at instances of expr or in blocks of num lines. If * is given instead of n, repeat argument until input is
exhausted.
Examples
Create up to 20 chapter files from the file novel:
csplit -k -f chap. novel '/CHAPTER/' '{20}'
Create up to 100 address files (xx00 through xx99),
each four lines long, from a database named address_list:
csplit -k address_list 4 {99}
|
ctags | ctags [options] files Create a list of function and macro names that are defined in the
specified C, C++, FORTRAN, Java, Perl, yacc, or other source
files. The output list (named
tags by default) contains lines of the form:
name file context
where name is the function or macro name,
file is the source file in which
name is defined, and context
is a search pattern that shows the line of code containing
name. After the list of tags is created, you can
invoke vi on any file and type:
:set tags=tagsfile
:tag name
This switches the vi editor to the
source file associated with the name listed in
tagsfile (which you specify with -t).
etags produces an equivalent file for tags to be used with Emacs.
Options
- -a, --append
Append tag output to existing list of tags.
- -d, --defines
Include tag entries for C preprocessor definitions.
- -i file, --include=file
Add a note to the tags file that file should be consulted in
addition to the normal input file.
- -l language, --language=language
Consider the files that follow this option to be written in
language. Use the -h option for a list of languages and
their default filename extensions.
- -o file, --output=file
Write to file.
- -rregexp, --regex=regexp
Include a tag for each line that matches regexp in the files following this option.
- -R, --no-regex
Don't include tags based on regular-expression matching for the files that follow this option.
- -t, --typedefs
Include tag entries for typedefs.
- -u, --update
Update tags file to reflect new locations of functions (e.g.,
when functions are moved to a different source file).
Old tags are deleted; new tags are appended.
- -v, --vgrind
Print to standard output a listing (index) of each function, source file,
and page number (1 page = 64 lines).
- -w, --no-warn
Suppress warning messages.
- -x, --cxref
Produce a listing of each function, and its line number,
source file, and context.
- -B, --backward-search
Search for tags backward through files.
- -C, --c++
Expect .c and .h files to contain C++, not C, code.
- -H, -h, --help
Print usage information and exit.
- -S, --ignore-indentation
Normally ctags uses indentation to parse the tag file; this option
tells it to rely on it less.
- -T, --typedefs-and-c++
Include tag entries for typedefs, structs, enums, unions, and C++
member functions.
- -V, --version
Print the version number and exit.
|
cut | cut options [files] Cut out selected columns or fields from one or more files.
In the following options, list is a sequence of integers.
Use a comma between separate values
and a hyphen to specify a range (e.g., 1-10,15,20 or 50-).
See also paste and join.
Options
- -b list, --bytes list
Specify list of positions; only bytes in these
positions will be printed.
- -c list, --characters list
Cut the column positions identified in list.
- -d c, --delimiter c
Use with -f to specify field delimiter as character c
(default is tab); special characters (e.g., a space) must be quoted.
- -f list, --fields list
Cut the fields identified in list.
- -n
Don't split multibyte characters.
- -s, --only-delimited
Use with -f to suppress lines without delimiters.
- --output-delimiter=string
Use string as the output delimiter. By default,
the output delimiter is the same as the input delimiter.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
Examples
Extract usernames and real names from
/etc/passwd:
cut -d: -f1,5 /etc/passwd
Find out who is logged on, but list only login names:
who | cut -d"" -f1
Cut characters in the fourth column of file, and
paste them back as the first column in the same file:
cut -c4 file | paste - file
|
date | date [options] [+format] [date] Print the current date and time. You may
specify a display format.
format can consist of literal text strings (blanks must be quoted)
as well as field descriptors, whose values will appear as described in the
following entries (the listing shows some logical groupings). A
privileged user can change the system's date and time.
Options
- +format
Display current date in a nonstandard format. For example:
% date +"%A %j %n%k %p"
Tuesday 248
15 PM
The default is
%a %b %e %T %Z %Y -- e.g., Tue Sep 5 14:59:37 EDT 2000.
- -d date, --date date
Display date, which should be in quotes and may be in the format
d days or
m months d days to print a date in the future. Specify ago to print a date in the past. You may
include formatting (see the "Format" section that follows).
- -f datefile, --file=datefile
Like -d but printed once for each line of
datefile.
- -I [timespec], --iso-8601[=timespec]
Display in ISO-8601 format. If specified, timespec can have one of the
values date (for date only), hours,
minutes, or seconds to get
the indicated precision.
- -r file, --reference=file
Display the time file was last modified.
- -R, --rfc-822
Display the date in RFC 822 format.
- --help
Print help message and exit.
- --version
Print version information and exit.
- -s date, --set date
Set the date.
- -u, --universal
Set the date to Greenwich Mean Time, not local time.
Format
- %
Literal %.
- -
Do not pad fields (default: pad fields with zeros).
- _
Pad fields with space (default: zeros).
- %a
Abbreviated weekday.
- %b
Abbreviated month name.
- %c
Country-specific date and time format.
- %d
Day of month (01-31).
- %h
Same as %b.
- %j
Julian day of year (001-366).
- %k
Hour in 24-hour format, without leading zeros (0-23).
- %l
Hour in 12-hour format, without leading zeros (1-12).
- %m
Month of year (01-12).
- %n
Insert a new line.
- %p
String to indicate AM or PM.
- %r
Time in
%I:%M:%S %p
(12-hour) format.
- %s
Seconds since "The Epoch,"
1970-01-01 00:00:00 UTC (a nonstandard extension).
- %t
Insert a tab.
- %w
Day of week (Sunday = 0).
- %x
Country-specific date format.
- %y
Last two digits of year (00-99).
- %z
RFC 822-style numeric time zone.
- %A
Full weekday.
- %B
Full month name.
- %D
Date in %m/%d/%y format.
- %H
Hour in 24-hour format (00-23).
- %I
Hour in 12-hour format (01-12).
- %M
Minutes (00-59).
- %S
Seconds (00-59).
- %T
Time in %H:%M:%S format.
- %U
Week number in year (00-53); start week on Sunday.
- %V
Week number in year (01-52); start week on Monday.
- %W
Week number in year (00-53); start week on Monday.
- %X
Country-specific time format.
- %Y
Four-digit year (e.g., 1996).
- %Z
Time zone name.
Strings for setting date
Strings for setting the date may be numeric or nonnumeric.
Numeric strings consist of time, day, and year in the format
MMDDhhmm[[CC]YY][.ss]. Nonnumeric strings
may include month strings, time zones, a.m., and p.m.
- time
A two-digit hour and two-digit minute
(hhmm); hh uses 24-hour format.
- day
A two-digit month and two-digit day of month (MMDD);
default is current day and month.
- year
The year specified as either the full four-digit century and year or
just the two-digit year; the default is the current year.
Examples
Set the date to July 1 (0701), 4 a.m. (0400), 1995 (95):
date 0701040095
The command:
date +"Hello%t Date is %D %n%t Time is %T"
produces a formatted date as follows:
Hello Date is 05/09/93
Time is 17:53:39
|
dd | dd options Make a copy of an input file (if)
using the specified conditions,
and send the results to the output file (or standard output if
of is not specified). Any number of
options can be supplied, although if
and of are the most common and are
usually specified first. Because dd
can handle arbitrary blocksizes, it is useful when converting between
raw physical devices.
Options
- bs=n
Set input and output blocksize to n bytes;
this option overrides ibs and obs.
- cbs=n
Set the size of the conversion buffer (logical record length)
to n bytes. Use only if the conversion
flag is ascii,
ebcdic, ibm,
block, or
unblock.
- conv=flags
Convert the input according to one or more (comma-separated)
flags listed next. The first five
flags are mutually exclusive.
- ascii
EBCDIC to ASCII.
- ebcdic
ASCII to EBCDIC.
- ibm
ASCII to EBCDIC with IBM conventions.
- block
Variable-length records (i.e., those terminated by a newline)
to fixed-length records.
- unblock
Fixed-length records to variable-length.
- lcase
Uppercase to lowercase.
- ucase
Lowercase to uppercase.
- noerror
Continue processing after read errors.
- notrunc
Don't truncate output file.
- swab
Swap each pair of input bytes.
- sync
Pad input blocks to ibs with trailing
zeros.
- count=n
Copy only n input blocks.
- ibs=n
Set input blocksize to n bytes (default is 512).
- if=file
Read input from file (default is standard input).
- obs=n
Set output blocksize to n bytes (default is 512).
- of=file
Write output to file (default is standard output).
- seek=n
Skip n output-sized blocks from start of output file.
- skip=n
Skip n input-sized blocks from start of input file.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
You can multiply size values (n) by a factor of 1024, 512, or 2 by
appending the letter k, b, or w, respectively.
You can use the letter x as a multiplication operator between two numbers.
Examples
Convert an input file to all lowercase:
dd if=caps_file of=small_file conv=lcase
Retrieve variable-length data; write it as fixed-length to
out:
data_retrieval_cmd | dd of=out conv=sync,block
|
debugfs | debugfs [[option] device] System administration command.
Debug an ext2 filesystem. device is the special file
corresponding to the device containing the ext2 filesystem
(e.g., /dev/hda3).
Option
- -w
Open the filesystem read-write.
Commands
- cat file
Dump the contents of an inode to standard output.
- cd directory
Change the current working directory to directory.
- chroot directory
Change the root directory to be the specified inode.
- close
Close the currently open filesystem.
- clri file
Clear the contents of the inode corresponding to file.
- dump file out_file
Dump the contents of an inode to out_file.
- expand_dir directory
Expand directory.
- find_free_block [goal]
Find first free block starting from goal (if specified) and allocate it.
- find_free_inode [dir [mode]]
Find a free inode and allocate it.
- freeb block
Mark block as not allocated.
- freei file
Free the inode corresponding to file.
- help
Print a list of commands understood by debugfs.
- icheck block
Do block-to-inode translation.
- initialize device blocksize
Create an ext2 filesystem on device.
- kill_file file
Remove file and deallocate its blocks.
- ln source_file dest_file
Create a link.
- ls [pathname]
Emulate the ls command.
- modify_inode file
Modify the contents of the inode corresponding to file.
- mkdir directory
Make directory.
- mknod file [p|[[c|b] major minor]]
Create a special device file.
- ncheck inode
Do inode-to-name translation.
- open [-w] device
Open a filesystem.
- pwd
Print the current working directory.
- quit
Quit debugfs.
- rm file
Remove file.
- rmdir directory
Remove directory.
- setb block
Mark block as allocated.
- seti file
Mark in use the inode corresponding to file.
- show_super_stats
List the contents of the super block.
- stat file
Dump the contents of the inode corresponding to file.
- testb block
Test whether block is marked as allocated.
- testi file
Test whether the inode corresponding to file is marked as allocated.
- unlink file
Remove a link.
- write source_file file
Create a file in the filesystem named file, and copy the
contents of source_file into the destination file.
|
depmod | depmod [options] modules System administration command.
Create a dependency file for the modules given on the
command line. This dependency file can be used by
modprobe to automatically load the relevant
modules. The normal use of depmod is to include the
line /sbin/depmod -a in one of the files in /etc/rc.d so
the correct module dependencies will be available after booting
the system.
Options
- -a
Create dependencies for all modules listed in /etc/conf.modules.
- -d
Debug mode. Show all commands being issued.
- -e
Print a list of all unresolved symbols.
- -v
Print a list of all processed modules.
Files
- /etc/conf.modules
Information about modules: which ones depend on others,
and which directories correspond to particular types of
modules.
- /sbin/insmod, /sbin/rmmod
Programs that depmod relies on.
|
df | df [options] [name] Report the amount of free disk space available on all
mounted filesystems or on the given name.
(df cannot report
on unmounted filesystems.) Disk space is shown in 1KB blocks
(default) or 512-byte blocks (if the
environment variable POSIXLY_CORRECT is set).
name can be a device name (e.g.,
/dev/hd*), the directory name of a mounting point (e.g.,
/usr), or a directory name (in which case df
reports on the entire filesystem in which that directory is mounted).
Options
- -a, --all
Include empty filesystems (those with 0 blocks).
- --block-size=n
Show space as n-byte blocks.
- -h, --human-readable
Print sizes in a format friendly to human readers (e.g., 1.9G instead of
1967156).
- -H, --si
Like -h, but show as power of
1000 rather than 1024.
- -i, --inodes
Report free, used, and percent-used inodes.
- -k, --kilobytes
Print sizes in kilobytes.
- -l, --local
Show local filesystems only.
- -m, --megabytes
Print sizes in megabytes.
- --no-sync
Show results without invoking sync
first (i.e., without flushing the buffers). This is the default.
- -P, --portability
Use POSIX output format (i.e., print information about each
filesystem on exactly one line).
- --sync
Invoke sync (flush buffers) before
getting and showing sizes.
- -t type, --type=type
Show only type filesystems.
- -T, --print-type
Print the type of each filesystem in addition to the sizes.
- -x type, --exclude-type=type
Show only filesystems that are not of type type.
- --help
Print help message and then exit.
- --version
Print the version and then exit.
|
diff | diff [options] [diroptions] file1 file2 Compare two text files. diff reports lines
that differ between file1 and
file2. Output consists of lines of context from each file,
with file1 text flagged by a
< symbol and file2
text by a > symbol. Context lines are
preceded by the ed command
(a, c,
or d) that would be used to convert
file1 to file2. If one of the
files is -, standard
input is read. If one of the files is a directory,
diff locates
the filename in that directory corresponding to the other argument
(e.g., diff my_dir junk is the same as
diff my_dir/junk
junk). If both arguments are directories,
diff reports lines
that differ between all pairs of files having equivalent names (e.g.,
olddir/program and newdir/program);
in addition, diff lists filenames unique to
one directory, as well as
subdirectories common to both. See also cmp.
Options
- -a, --text
Treat all files as text files. Useful for checking to see if binary
files are identical.
- -b, --ignore-space-change
Ignore repeating blanks and end-of-line blanks; treat successive blanks
as one.
- -B, --ignore-blank-lines
Ignore blank lines in files.
- -c
Context diff: print 3 lines surrounding each changed line.
- -C n, --context[=n]
Context diff: print n lines surrounding each changed line. The default context is 3 lines.
- -d, --minimal
To speed up comparison, ignore segments of numerous changes and output
a smaller set of changes.
- -Dsymbol, --ifdef=symbol
When handling C files, create an output file that
contains all the contents of both input files, including #ifdef and #ifndef directives that reflect the directives
in both files.
- -e, --ed
Produce a script of commands (a,
c, d) to
re-create file2 from file1 using the
ed editor.
- -F regexp, --show-function-line[=regexp]
For context and unified diff, show the most recent line containing
regexp before each block of changed lines.
- -H
Speed output of large files by scanning for scattered small
changes; long stretches with many changes may not show up.
- --help
Print brief usage message.
- --horizon-lines=n
In an attempt to find a more compact listing, keep
n lines on both sides of the changed lines when
performing the comparison.
- -i, --ignore-case
Ignore case in text comparison. Uppercase and lowercase are considered the same.
- -I regexp, --ignore-matching-lines=regexp
Ignore lines in files that match the regular expression
regexp.
- -l, --paginate
Paginate output by passing it to pr.
- -L label, --label label, --label=label
For context and unified diff, print
label in place of the filename being
compared. The first such option applies to the first filename and the
second option to the second filename.
- --left-column
For two-column output (-y),
show only left column of common lines.
- -n, --rcs
Produce output in RCS diff format.
- -N, --new-file
Treat nonexistent files as empty.
- -p, --show-c-function
When handling files in C or C-like languages such as
Java, show the function containing each block of changed
lines. Assumes -c but can also
be used with a unified diff.
- -P, --unidirectional-new-file
If two directories are being compared and the first
lacks a file that is in the second, pretend that an empty file of that
name exists in the first directory.
- -q, --brief
Output only whether files differ.
- -r, --recursive
Compare subdirectories recursively.
- -s, --report-identical-files
Indicate when files do not differ.
- -S filename, --starting-file=filename
For directory comparisons, begin with the file filename,
skipping files that come earlier in the standard list order.
- --suppress-common-lines
For two-column output (-y), do not
show common lines.
- -t, --expand-tabs
Produce output with tabs expanded to spaces.
- -T, --initial-tab
Insert initial tabs into output to line up tabs properly.
- -u
Unified diff: print old and new versions of
lines in a single block, with 3 lines surrounding each block of changed lines.
- -U n, --unified[=n]
Unified diff: print old and new
versions of lines in a single block, with n lines
surrounding each block of changed lines. The default context is 3 lines.
- -v, --version
Print version number of this version of diff.
- -w, --ignore-all-space
Ignore all whitespace in files for comparisons.
- -W n, --width=n
For two-column output (-y), produce
columns with a maximum width of n characters.
Default is 130.
- -x regexp, --exclude=regexp
Do not compare files in a directory whose names match
regexp.
- -X filename, --exclude-from=filename
Do not compare files in a directory whose names match patterns described
in the file filename.
- -y, --side-by-side
Produce two-column output.
- -n
For context and unified diff, print
n lines of context. Same as specifying a number
with -C or -U.
|
diff3 | diff3 [options] file1 file2 file3 Compare 3 files and report the differences. No more than one of
the files may be given as - (indicating
that it is to be read from standard input). The output is displayed with
the following codes:
- ====
All three files differ.
- ====1
file1 is different.
- ====2
file2 is different.
- ====3
file3 is different.
diff3 is also designed to merge changes in two
differing files
based on a common ancestor file (i.e., when two people have made their own
set of changes to the same file). diff3 can find changes between
the ancestor and one of the newer files and generate output that
adds those differences to the other new file.
Unmerged changes are places where both of the newer files differ
from each other and at least one of them from the ancestor.
Changes from the ancestor that are the same in
both of the newer files are called merged changes.
If all three files differ in the same place, it is called an overlapping
change.
This scheme is used on the command line with the ancestor being
file2, the second filename. Comparison is made between file2
and file3, with those differences then applied to file1.
Options
- -3, --easy-only
Create an ed script to incorporate into file1
unmerged, nonoverlapping differences between file1 and file3.
- -a, --text
Treat files as text.
- -A, --show-all
Create an ed script to incorporate all changes, showing conflicts in
bracketed format.
- -e, --ed
Create an ed script to incorporate into file1
all unmerged differences between file2 and file3.
- -E, --show-overlap
Create an ed script to incorporate unmerged changes, showing conflicts
in bracketed format.
- -x, --overlap-only
Create an ed script to incorporate into file1 all
differences where all three files differ (overlapping changes).
- -X
Same as -x, but show
only overlapping changes, in bracketed format.
- -m, --merge
Create file with changes merged (not an ed
script).
- -L label, --label=label
Use label to replace filename in output.
- -i
Append the w (save) and q (quit) commands to ed
script output.
- -T, --initial-tab
Begin lines with a tab instead of two spaces in output to
line tabs up properly.
- -v, --version
Print version information and then exit.
|
dip | dip [options] [chat scriptfile] System administration command.
Set up or initiate dial-up Internet connections. dip can be used
to establish connections for users dialing out or dialing in.
Commands can be used in interactive mode or placed in a script file
for use in dial-out connections. To establish dial-in connections,
dip is often is used as a shell and may be executed using the
commands diplogin or diplogini.
Options
- -a
In dial-in mode, prompt for username and password. Same as
the diplogini command.
- -i
Initiate a login shell for a dial-in connection. Same as the
diplogin command.
- -k
Kill the most recent dip process or the process running
on the device specified by the -l option.
- -l device
Used with the -k option. Specifies a tty device.
- -m mtu
Maximum Transfer Unit. The default is 296.
- -p protocol
The protocol to use: SLIP, CSLIP, PPP, or TERM.
- -t
Command mode. This is usually done for testing.
- -v
Verbose mode.
Commands
Most of these commands can be used either in interactive mode
or in a script file.
- beep times
Beep the terminal the specified number of times.
- bootp
Retrieve local and remote IP addresses using the BOOTP protocol.
- break
Send a BREAK.
- chatkey keyword code
Map a modem response keyword to a numeric code.
- config [interface|routing] [pre|up|down|post] arguments
Modify interface characteristics or the routing table,
before the link comes up, when it is up, when it goes down, or
after it is down. The syntax for arguments is the same as
arguments for the ifconfig or route
commands.
- databits 7|8
Set the number of data bits.
- dec $variable [value]
Decrement $variable by value. The default is 1.
- default
Set default route to the IP address of the host connected to.
- dial phonenumber [timeout]
Dial phonenumber. Abort if remote modem doesn't answer
within timeout seconds. Set $errlvl according to
the modem response.
- echo on|off
Enable or disable the display of modem commands.
- exit [n]
Exit the script. Optionally return the number n as the exit
status.
- flush
Clear the input buffer.
- get $variable [ask|remote [timeout]] value
Set $variable to value. If ask is specified, prompt
the user for a value. If remote is specified, retrieve the
value from the remote system. Abort after timeout
seconds.
- goto label
Jump to the section identified by label.
- help
List available commands.
- if expr goto label
Jump to the section identified by label if the expression
evaluates to true. An expression compares a variable to a constant
using one of these operators: =, !=, <, >, <=, or >=.
- inc $variable [value]
Increment $variable by value. The default is 1.
- init string
Set the string used to initialize the modem. The default
is ATE0 Q0 V1 X1.
- mode protocol
Set the connection protocol. Valid values are SLIP, CSLIP, PPP,
and TERM. The default is SLIP.
- netmask mask
Set the subnet mask.
- parity E|O|N
Set the line parity to even, odd, or none.
- password
Prompt user for password.
- proxyarp
Install a proxy ARP entry in the local ARP table.
- print $variable
Display the content of $variable.
- psend command
Execute command in a shell, and send output to the
serial device. Commands are executed using the user's
real UID.
- port device
Specify the serial device the modem is attached to.
- quit
Exit with a nonzero exit status. Abort the connection.
- reset
Reset the modem.
- securid
Prompt user for the variable part of an ACE System SecureID password
and send it together with the stored prefix to the remote system.
- securidf prefix
Store the fixed part of an ACE System SecureID password.
- send string
Send string to the serial device.
- shell command
Execute command in a shell using the user's real UID.
- skey [timeout]
Wait for an S/Key challenge, then prompt user for the secret key. Generate and send the response. Abort if challenge is not received
within timeout seconds. S/Key support must be compiled into
dip.
- sleep time
Wait time seconds.
- speed bits-per-second
Set the port speed. Default is 38400.
- stopbits 1|2
Set the number of stop bits.
- term
Enable terminal mode. Pass keyboard input directly to the serial
device.
- timeout time
Set the number of seconds the line can be inactive before the
link is closed.
- wait text [timeout]
Wait timeout seconds for text to arrive from the remote
system. If timeout is not specified, wait forever.
|
dirname | dirname pathname Print pathname excluding the last level.
Useful for stripping the actual filename from a pathname. If there
are no slashes (no directory levels) in pathname,
dirname prints .
to indicate the current directory.
See also basename.
|
dmesg | dmesg [options] System administration command.
Display the system control messages from the kernel ring buffer.
This buffer stores all messages since the last system boot or
the most recent ones, if the buffer has been filled.
Options
- -c
Clear buffer after printing messages.
- -n level
Set the level of system message that will display on console.
|
dnsdomainname | dnsdomainname TCP/IP command. Print the system's DNS domain name.
See also hostname.
|
domainname | domainname [name] NFS/NIS command. Set or display name of current NIS domain.
With no argument, domainname
displays the name of the current NIS domain. Only a privileged user can set the
domain name by giving an argument; this is usually done in a startup script.
|
dosfsck |
dosfsck [options] device fsck.ext2 [options] device System administration command. Similar to fsck, but specifically intended for MS-DOS
filesystems. When checking an MS-DOS filesystem, fsck calls this command. Normally
dosfsck
stores all changes in memory, then
writes them when checks are complete.
Options
- -a
Automatically repair the system; do not prompt the user.
- -A
Use the Atari version of the MS-DOS filesystem.
- -d file
Drop the named file from the file allocation table. Force checking, even if kernel has already marked the filesystem as valid. dosfsck will normally exit without
checking if the system appears to be clean.
- -l file
Consult file for a list of bad blocks, in addition
to checking for others.
- -n
Ensure that no changes are made to the filesystem.
When queried, answer "no."
- -p
"Preen." Repair all bad blocks noninteractively.
- -t
Display timing statistics.
- -v
Verbose.
- -y
When queried, answer "yes."
- -B size
Expect to find the superblock at size; if it's not
there, exit.
- -F
Flush buffer caches before checking.
- -L file
Consult file for list of bad blocks instead of
checking filesystem for them.
|
du | du [options] [directories] Print disk usage (as the number of 1KB blocks used
by each named directory and its subdirectories; default is current directory).
Options
- -a, --all
Print usage for all files, not just subdirectories.
- -b, --bytes
Print sizes in bytes.
- -c, --total
In addition to normal output, print grand total of all arguments.
- -D, --dereference-args
Follow symbolic links, but only if they are command-line
arguments.
- -h, --human-readable
Print sizes in human-reader-friendly format.
- -H, --si
Like -h, but show as power of
1000 rather than 1024.
- -k, --kilobytes
Print sizes in kilobytes (this is the default).
- -l, --count-links
Count the size of all files, whether or not they have already
appeared (i.e., via a hard link).
- -L, --dereference
Follow symbolic links.
- --exclude=pattern
Exclude files that match pattern.
- --max-depth=num
Report sizes for directories only down to
num levels below the starting point (which is level 0).
- -m, --megabytes
Print sizes in megabytes.
- -s, --summarize
Print only the grand total for each named directory.
- -S, --separate-dirs
Do not include the sizes of subdirectories when totaling the
size of parent directories.
- -x, --one-file-system
Display usage of files in current filesystem only.
- -X, --exclude-from=file
Exclude files that match any pattern in file.
- --help
Print help message and then exit.
- --version
Print the version and then exit.
|
dumpe2fs | dumpe2fs device System administration command.
Print information about device's superblock and blocks group.
|
dumpkeys | dumpkeys [options] Print information about the keyboard driver's translation tables to
standard output. Further information is available in the manual pages under
keytables.
Options
- -1, --separate-lines
Print one line for each modifier/keycode pair and prefix plain to
each unmodified keycode.
- -ccharset, --charset=charset
Specify character set with which to interpret character code
values. The default character set is iso-8859-1.
The full list of valid character sets is available with the
--help option.
- --compose-only
Print compose key combinations only. Requires
compose key support in the kernel.
- -f, --full-table
Output in canonical, not short, form: for each key, print a row
with modifier combinations divided into columns.
- --funcs-only
Print function key string definitions only; do not print
key bindings or string definitions.
- -h, --help
Print help message and the version.
- -i, --short-info
Print in short-info format, including information about acceptable
keycode keywords in the keytable files; the number of actions that can
be bound to a key; a list of the ranges of action codes (the values to the
right of a key definition); and the number of function keys that the
kernel supports.
- --keys-only
Print key bindings only; do not print string definitions.
- -l, --long-info
Print the same information as in --short-info, plus a list of the
supported action symbols and their numeric
values.
- -n, --numeric
Print action code values in hexadecimal notation; do not attempt
to convert them to symbolic notation.
- -S num, --shape=num
Print using num to determine table shape. Values of
num are:
- 0
Default
- 1
Same as --full-table
- 2
Same as --separate-lines
- 3
One line for each keycode up to the first hole, then one line per
modifier/keycode pair
|
e2fsck | e2fsck [options] device fsck.ext2 [options] device System administration command.
Similar to fsck, but specifically intended for Linux
Second Extended Filesystems. When checking a second extended
filesystem, fsck calls this command.
Options
- -b superblock
Use superblock instead of default superblock.
- -d
Debugging mode.
- -f
Force checking, even if kernel has already marked the filesystem as valid. e2fsck will normally exit without
checking if the system appears to be clean.
- -l file
Consult file for a list of bad blocks, in addition
to checking for others.
- -n
Ensure that no changes are made to the filesystem.
When queried, answer "no."
- -p
"Preen." Repair all bad blocks noninteractively.
- -t
Display timing statistics.
- -v
Verbose.
- -y
When queried, answer "yes."
- -B size
Expect to find the superblock at size; if it's not
there, exit.
- -F
Flush buffer caches before checking.
- -L file
Consult file for list of bad blocks instead of
checking filesystem for them.
|
echo | echo [-n] [string] This is the /bin/echo command. echo also exists
as a command built into the C shell and bash. The following
character sequences have special meanings:
- \a
Alert (bell)
- \b
Backspace
- \c
Suppress trailing newline
- \f
Form feed
- \n
Newline
- \r
Carriage return
- \t
Horizontal tab
- \v
Vertical tab
- \\
Literal backslash
- \nnn
The octal character whose ASCII code is nnn.
Options
- -e
Enable character sequences with special meaning. (In some versions,
this option is not required in order to make the sequences work.)
- -E
Disable character sequences with special meaning.
- -n
Suppress printing of newline after text.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
Examples
/bin/echo "testing printer" | lp
/bin/echo "TITLE\nTITLE" > file ; cat doc1 doc2 >> file
/bin/echo "Warning: ringing bell \a"
|
egrep | egrep [options] [regexp] [files] Search one or more files for lines that match an
extended regular expression regexp.
egrep doesn't support
the regular expressions \(, \), \n, \<, \>, \{,
or \} but does support the other expressions, as well as
the extended set +, ?, |, and
( ).
Remember to enclose these characters in quotes.
Regular expressions are described in Chapter 9, "Pattern Matching".
Exit status is 0 if any lines match, 1 if none match, and 2 for errors.
See grep for the list of available options.
Also see fgrep.
egrep typically runs faster than those
commands.
Examples
Search for occurrences of Victor or Victoria in file:
egrep 'Victor(ia)*' file
egrep '(Victor|Victoria)' file
Find and print strings such as old.doc1 or new.doc2 in files,
and include their line numbers:
egrep -n '(old|new)\.doc?' files
|
emacs | emacs [options] [files] A text editor and all-purpose work environment. For more
information, see Chapter 10, "The Emacs Editor".
|
env | env [option] [variable=value ... ] [command] Display the current environment or, if an environment variable is
specified, set it to a new value and display the modified
environment. If command is specified,
execute it under the modified environment.
Options
- -, -i, --ignore-environment
Ignore current environment entirely.
- -u name, --unset name
Unset the specified variable.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
|
etags | etags [options] files Create a list of function and macro names that are defined in the
specified C, Pascal, FORTRAN, yacc,
or flex source
files. The output list (named tags by default) contains lines of the form:
name file context
where name is the function or macro name,
file is the source file in which
name is defined, and context
is a search pattern that shows the line of code containing
name. After the list of tags is created, you can
invoke Emacs on any file and type:
ESC-x visit-tags-table
You will be prompted for the name of the tag table; the default is
TAGS. To switch to the source file associated with the
name listed in tagsfile,
type:
ESC-x find-tag
You will be prompted for the tag you would like Emacs to search for.
ctags produces an equivalent tags
file for use with vi.
Options
- -a, --append
Append tag output to existing list of tags.
- -d, --defines
Include tag entries for C preprocessor definitions.
- -i file, --include=file
Add a note to the tags file that file should be consulted in
addition to the normal input file.
- -l language, --language=language
Consider the files that follow this option to be written in
language. Use the -h option for a list of languages and
their default filename extensions.
- -o file, --output=file
Write to file.
- -r regexp, --regex=regexp
Include a tag for each line that matches regexp in the files
following this option.
- -C, --c++
Expect .c and .h files to contain C++, not C, code.
- -D, --no-defines
Do not include tag entries for C preprocessor definitions.
- -H, -h, --help
Print usage information.
- -R, --noregex
Don't include tags based on regular-expression matching for the files
that follow this option.
- -S, --ignore-indentation
Normally etags uses indentation to parse the tag file; this option
tells it to rely on it less.
- -V, --version
Print the version number.
|
ex | ex [options] file An interactive command-based editor. For more information, see Chapter 11, "The vi Editor".
|
expand | expand [options] files Convert tabs in given files (or standard input, if the file is named
-) to appropriate number of spaces; write results to standard output.
Options
- -tabs, -t, --tabs tabs
tabs is a comma-separated list of integers that
specify the placement of tab stops.
If exactly one integer is provided, the tab stops are set to every
integer spaces. By default, tab stops are 8 spaces apart.
With -t and --tabs, the list may be separated by whitespace instead of commas.
- -i, --initial
Convert tabs only at the beginning of lines.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
|
expr | expr arg1 operator arg2 [ operator arg3 ... ] Evaluate arguments as expressions and print the result.
Arguments and operators must be separated by spaces.
In most cases, an argument is an integer, typed literally or
represented by a shell variable.
There are three types of operators: arithmetic, relational, and logical,
as well as keyword expressions.
Exit status for expr is 0 (expression is nonzero and nonnull),
1 (expression is 0 or null), or 2 (expression is invalid).
Arithmetic operators
Use these to produce mathematical expressions whose results are printed:
- +
Add arg2 to arg1.
- -
Subtract arg2 from arg1.
- *
Multiply the arguments.
- /
Divide arg1 by arg2.
- %
Take the remainder when arg1 is divided
by arg2.
Addition and subtraction are evaluated last, unless they are grouped inside
parentheses. The symbols *, (, and ) have meaning to the shell,
so they must be escaped (preceded by a backslash or enclosed in single
quotes).
Relational operators
Use these to compare two arguments. Arguments can also be words, in which
case comparisons are defined by the locale.
If the comparison statement is true, the result is 1; if false,
the result is 0. Symbols > and < must be escaped.
- =, ==
Are the arguments equal?
- !=
Are the arguments different?
- >
Is arg1 greater than arg2?
- >=
Is arg1 greater than or equal to arg2?
- <
Is arg1 less than arg2?
- <=
Is arg1 less than or equal to arg2?
Logical operators
Use these to compare two arguments. Depending on the values,
the result can be arg1 (or some portion of it), arg2, or 0.
Symbols | and & must be escaped.
- |
Logical OR; if arg1 has a nonzero (and nonnull) value,
the result is arg1; otherwise, the result is arg2.
- &
Logical AND; if both arg1 and arg2 have a nonzero
(and nonnull) value, the result is arg1; otherwise,
the result is 0.
- :
Like grep; arg2 is a pattern to search for in arg1.
arg2 must be a regular expression. If part of the arg2 pattern
is enclosed in \( \), the result is the portion of arg1 that matches;
otherwise, the result is simply the number of characters that match. By
default, a
pattern match always applies to the beginning of the first argument (the search
string implicitly begins with a ^). Start the search string with .*
to match other parts of the string.
Keywords
- index string character-list
Return the first position in string that matches the first possible
character in character-list. Continue
through character-list
until a match is found, or return 0.
- length string
Return the length of string.
- match string regex
Same as string : regex.
- quote token
Treat token as a string, even if it would
normally be a keyword or an operator.
- substr string start length
Return a section of string, beginning with
start, with a maximum length of
length characters. Return null when given a
negative or nonnumeric start or
length.
Examples
Division happens first; result is 10:
expr 5 + 10 / 2
Addition happens first; result is 7 (truncated from 7.5):
expr \( 5 + 10 \) / 2
Add 1 to variable i. This is how variables are incremented in
shell scripts:
i=`expr $i + 1
Print 1 (true) if variable a is the string "hello":
expr $a = hello
Print 1 (true) if b plus 5 equals 10 or more:
expr $b + 5 \>= 10
Find the 5th, 6th, and 7th letters of the word character:
expr substr character 5 3
In the examples that follow, variable p is the
string "version.100". This command prints the number of characters in
p:
expr $p : '.*' Result is 11
Match all characters and print them:
expr $p : '\(.*\)' Result is "version.100"
Print the number of lowercase letters at the beginning of p:
expr $p : '[a-z]*' Result is 7
Match the lowercase letters at the beginning of p:
expr $p : '\([a-z]*\)' Result is "version"
Truncate $x if it contains five or more characters;
if not, just print $x. (Logical OR uses the second argument when
the first one is 0 or null; i.e., when the match fails.)
expr $x : '\(.....\)' \| $x
In a shell script, rename files to their first five letters:
mv $x `expr $x : '\(.....\)' \| $x
(To avoid overwriting files with similar names, use mv -i.)
|
false | false A null command that returns an unsuccessful (nonzero) exit status.
Normally used in bash scripts. See also true.
|
fdformat | fdformat [options] device Low-level format of a floppy disk. The device for a standard format is
usually /dev/fd0 or /dev/fd1.
Option
- -n
Do not verify format after completion.
|
fdisk | fdisk [options] [device] System administration command.
Maintain disk partitions via a menu.
fdisk displays information about disk
partitions, creates and deletes disk partitions, and changes the
active partition. It is possible to assign a different operating
system to each of the four partitions, though only one partition is
active at any given time. You can also divide a physical partition
into several logical partitions. The minimum recommended size for a Linux
system partition is 40MB. Normally, device will be
/dev/hda, /dev/hdb, /dev/sda, /dev/sdb,
/dev/hdc, /dev/hdd, and so on. See also cfdisk.
Options
- -l
List partition tables and exit.
- -spartition
Display the size of partition, unless it is a DOS partition.
Commands
- a
Toggle a bootable flag on current partition.
- d
Delete current partition.
- l
List all partition types.
- m
Main menu.
- n
Create a new partition; prompt for more information.
- p
Print a list of all partitions and information about each.
- q
Quit; do not save.
- t
Replace the type of the current partition.
- u
Modify the display/entry units, which must be
cylinders or sectors.
- v
Verify: check for errors; display a summary of the number
of unallocated sectors.
- w
Save changes; exit.
|
fetchmail | fetchmail [options] [servers...] System administration command.
Retrieve mail from mail servers and forward it to the
local mail delivery system. fetchmail retrieves
mail from servers that support the common mail protocols
POP2, POP3, IMAP2bis, and IMAP4. Messages are delivered via
SMTP through port 25 on the local host and through your
system's mail delivery agent (such as sendmail), where
they can be read through the user's mail client.
fetchmail settings are stored in the ~/.fetchmailrc
file.
Parameters and servers can also
be set on the command line, which will override settings
in the .fetchmailrc file.
fetchmail is compatible with the popclient program,
and users can use both without having to adjust file settings.
Options
- -a, --all
Retrieve all messages from server, even ones that
have already been seen but left on the server. The default
is to only retrieve new messages.
- -A type, --auth type
Specify the type of authentication. type
may be: password, kerberos_v5, or kerberos.
Authentication type is usually established by fetchmail by default,
so this option isn't very useful.
- -B n, --fetchlimit n
Set the maximum number of messages (n) accepted from
a server per query.
- -b n, --batchlimit n
Set the maximum number of messages sent to an SMTP
listener per connection. When this limit is reached, the
connection will be broken and reestablished. The default
of 0 means no limit.
- -c, --check
Check for mail on a single server without retrieving
or deleting messages. Works with IMAP but not well with
other protocols, if at all.
- -D [domain], --smtpaddress [domain]
Specify the domain name placed in RCPT TO
lines sent to SMTP. The default is the local host.
- -E header, --envelope header
Change the header assumed to contain the mail's
envelope address (usually "X-Envelope-to:") to header.
- -e n, --expunge n
Tell an IMAP server to EXPUNGE (i.e., purge messages marked
for deletion) after n deletes. A setting of 0 indicates
expunging only at the end of the session. Normally, an expunge
occurs after each delete.
- -F, --flush
For POP3 and IMAP servers, remove previously retrieved messages from
the server before retrieving new ones.
- -f file, --fetchmailrc file
Specify a nondefault name for the fetchmail configuration
file.
- -I specification, --interface specification
Require that the mail server machine is up and running at
a specified IP address (or range) before polling. The specification
is given as interface/ipaddress/mask. The first part indicates
the type of TCP connection expected (sl0, ppp0, etc.), the second
is the IP address, and the third is the bit mask for the IP, assumed to be
255.255.255.255.
- -K, --nokeep
Delete all retrieved messages from the mail server.
- -k, --keep
Keep copies of all retrieved messages on the mail server.
- -l size, --limit size
Set the maximum message size that will be retrieved from
a server. Messages larger than this size will be left on
the server and marked unread.
- -M interface, --monitor interface
In daemon mode, monitor the specified TCP/IP interface
for any activity besides itself, and skip the poll if
there is no
other activity. Useful for PPP connections that
automatically time out with no activity.
- -m command, --mda command
Pass mail directly to mail delivery agent, rather
than send to port 25. The command is
the path and options for the mailer, such as
/usr/lib/sendmail -oem. A %T
in the command will be replaced with the local
delivery address, and an %F will be replaced
with the message's From address.
- -n, --norewrite
Do not expand local mail IDs to full addresses.
This option will disable expected addressing and
should only be used to find problems.
- -P n, --port n
Specify a port to connect to on the mail server.
The default port numbers for supported protocols
are usually sufficient.
- -p proto, --protocol proto
Specify the protocol to use when polling a mail server.
proto can be:
- POP2
Post Office Protocol 2.
- POP3
Post Office Protocol 3.
- APOP
POP3 with MD5 authentication.
- RPOP
POP3 with RPOP authentication.
- KPOP
POP3 with Kerberos v4 authentication on port 1109.
- IMAP
IMAP2bis, IMAP4, or IMAP4rev1. fetchmail
autodetects their capabilities.
- IMAP-K4
IMAP4 or IMAP4rev1 with Kerberos v4 authentication.
- IMAP-GSS
IMAP4 or IMAP4rev1 with GSSAPI authentication.
- ETRN
ESMTP.
- -Q string, --qvirtual string
Remove the prefix string, which is the
local user's hostid, from the address in the envelope header
(such as "Delivered-To:").
- -r folder, --folder folder
Retrieve the specified mail folder from the
mail server.
- -s, --silent
Suppress status messages during a fetch.
- -U, --uidl
For POP3, track the age of kept messages via unique ID listing.
- -u name, --username name
Specify the user name to use when logging into
the mail server.
- -V, --version
Print the version information for fetchmail and display
the options set for each mail server. Performs no fetch.
- -v, --verbose
Display all status messages during a fetch.
- -Z nnn, --antispam nnn
Specify the SMTP error nnn to signal a
spam block from the client. If nnn is -1, this
option is disabled.
|
fgrep | fgrep [options] pattern [files] Search one or more files for lines that match a literal
text string pattern.
Exit status is 0 if any lines match, 1 if not, and 2 for errors.
See grep for the list of available options.
Also see egrep.
Examples
Print lines in file that don't contain
any spaces:
fgrep -v '' file
Print lines in file that contain the words in spell_list:
fgrep -f spell_list file
|
file | file [options] files Classify the named files according to the type of data they contain.
file checks the magic file
(usually /usr/share/magic) to identify some file types.
Options
- -b
Brief mode; do not prepend filenames to output lines.
- -c
Check the format of the magic file
(files argument is invalid with
-c). Usually used with
-m.
- -f file
Read the names of files to be checked from file.
- -L
Follow symbolic links. By default, symbolic links are not followed.
- -m file
Search for file types in file instead of
/usr/share/magic.
- -n
Flush standard output after checking a file.
- -s
Check files that are block or character special files in addition
to checking ordinary files.
- -v
Print the version.
- -z
Attempt checking of compressed files.
Many file types are understood. Output lists each filename,
followed by a brief classification such as:
ascii text
c program text
c-shell commands
data
empty
iAPX 386 executable
directory
[nt]roff, tbl, or eqn input text
shell commands
symbolic link to ../usr/etc/arp
Example
List all files that are deemed to be troff/nroff input:
file * | grep roff
|
find | find [pathnames] [conditions] An extremely useful command for finding particular groups of files
(numerous examples follow this description).
find descends the directory tree beginning at each pathname
and locates files that meet the specified conditions.
The default pathname is the current directory.
The most useful conditions include -print (which is the default
if no other expression is given),
-name and -type (for general use), -exec and
-size (for advanced users), and -mtime and -user
(for administrators).
Conditions may be grouped by enclosing them in \( \) (escaped
parentheses), negated with ! (use \! in the C shell), given as
alternatives by separating them with -o, or repeated (adding
restrictions to the match; usually only for -name, -type,
-perm).
Modification refers to editing of a file's contents. Change refers to
modification, permission or ownership changes, and so on; therefore, for example,
-ctime is more inclusive than -atime or -mtime.
Conditions and actions
- -atime +n | -n | n
Find files that were last accessed more than n (+n), less
than n (-n), or exactly n days ago. Note that
find changes the access time of directories supplied as
pathnames.
- -ctime +n | -n | n
Find files that were changed more than n (+n), less than
n (-n), or exactly n days ago. A change is
anything that changes the directory entry for the file, such as a
chmod.
- -depth
Descend the directory tree, skipping directories and working on actual
files first (and then the parent directories). Useful when files
reside in unwritable directories (e.g., when using find
with cpio).
- -exec command { } \;
Run the Linux command, from the starting directory
on each file matched by find
(provided command executes successfully on that file;
i.e., returns a 0 exit status). When command runs,
the argument { } substitutes the current file. Follow the entire sequence with an escaped semicolon (\;).
- -follow
Follow symbolic links and track the directories visited
(don't use this with -type l).
- -group gname
Find files belonging to group gname. gname can be a group
name or a group ID number.
- -inum n
Find files whose inode number is n.
- -links n
Find files having n links.
- -mount, -xdev
Search for files that reside only on the same filesystem as pathname.
- -mtime +n | -n | n
Find files that were last modified more than
n (+n), less
than n
(-n),
or exactly n days ago. A
modification is a change to a file's data.
- -name pattern
Find files whose names match pattern. Filename metacharacters
may be used but should be escaped or quoted.
- -newer file
Find files that have been modified more recently than file;
similar to -mtime. Affected by -follow only if it occurs after
-follow on the command line.
- -ok command { }\;
Same as -exec but prompts user
to respond with y
before command is executed.
- -perm nnn
Find files whose permission flags (e.g., rwx) match octal number
nnn exactly (e.g., 664 matches
-rw-rw-r--). Use a minus sign before nnn
to make a "wildcard" match of any unspecified octal digit
(e.g., -perm -600
matches -rw-******, where * can be any mode).
- -print
Print the matching files and directories, using their full pathnames.
Return true.
- -regex pattern
Like -path but uses grep-style regular
expressions instead of the shell-like globbing used in
-name and -path.
- -size n[c]
Find files containing n blocks, or if c is specified,
n characters long.
- -type c
Find files whose type is c. c can be b (block
special file), c (character special file), d
(directory), p (fifo or named pipe), l
(symbolic link), s (socket), or f (plain file).
- -user user
Find files belonging to user (name or ID).
- -daystart
Calculate times from the start of the day today, not 24 hours ago.
- -maxdepth num
Do not descend more than num levels of directories.
- -mindepth num
Begin applying tests and actions only at levels deeper than
num levels.
- -noleaf
Normally, find assumes that each directory has at least two hard links
that should be ignored (a hard link for its name and one for "."; i.e.,
two fewer "real" directories than its hard link count indicates).
-noleaf turns off this assumption, a useful practice when find
runs on non-Unix-style filesystems. This forces find to examine all
entries, assuming that some might prove to be directories into which
it must descend (a time-waster on Unix).
- -amin +n | -n | n
Find files last accessed more than n (+n), less than
n (-n), or exactly n minutes ago.
- -anewer file
Find files that were accessed after file was
last modified. Affected by -follow
when after -follow on the command line.
- -cmin +n | -n | n
Find files last changed more than n (+n), less than
n (-n), or exactly n minutes ago.
- -cnewer file
Find files that were changed after they were last modified.
Affected by -follow when after -follow on the command line.
- -empty
Continue if file is empty. Applies to regular files and directories.
- -false
Return false value for each file encountered.
- -fstype type
Match files only on type filesystems. Acceptable types include
minix, ext,
ext2, xia,
msdos, umsdos,
vfat, proc,
nfs, iso9660,
hpfs, sysv,
smb, and ncpfs.
- -gid num
Find files with numeric group ID of num.
- -ilname pattern
A case-insensitive version of -lname.
- -iname pattern
A case-insensitive version of -name.
- -ipath pattern
A case-insensitive version of -path.
- -iregex pattern
A case-insensitive version of -regex.
- -lname pattern
Search for files that are symbolic links, pointing to
files named pattern. pattern can include shell metacharacters
and does not treat / or . specially. The match is case-insensitive.
- -mmin +n | -n | n
Find files last modified more than n (+n), less than
n (-n), or exactly n minutes ago.
- -nouser
The file's user ID does not correspond to any user.
- -nogroup
The file's group ID does not correspond to any group.
- -path pattern
Find files whose names match pattern. Expect full pathnames
relative to the starting pathname (i.e., do not treat / or . specially).
Examples
List all files (and subdirectories) in your home directory:
find $HOME -print
List all files named chapter1 in the /work directory:
find /work -name chapter1 -print
List all files beginning with memo owned by ann:
find /work -name 'memo*' -user ann -print
Search the filesystem (begin at root) for manpage directories:
find / -type d -name 'man*' -print
Search the current directory, look for filenames that don't begin
with a capital letter, and send them to the printer:
find . \! -name '[A-Z]*' -exec lpr {}\;
Find and compress files whose names don't end with .gz:
gzip `find . \! -name '*.gz' -print
Remove all empty files on the system (prompting first):
find / -size 0 -ok rm {} \;
Search the system for files that were modified within the last two days
(good candidates for backing up):
find / -mtime -2 -print
Recursively grep for a pattern down a directory tree:
find /book -print | xargs grep '[Nn]utshell'
If the files kt1 and kt2 exist in the current directory,
their names can be printed with the command:
$ find . -name 'kt[0-9]'
./kt1
./kt2
Since the command prints these names with an initial ./
path, you need to specify the ./ when using the -path
option:
$ find . -path './kt[0-9]'
./kt1
./kt2
The -regex option uses a complete pathname, like
-path, but treats the following argument as a regular
expression rather than a glob pattern (although in this case
the result is the same):
$ find . -regex './kt[0-9]'
./kt1
./kt2
|
finger | finger [options] users Display data about one or more users, including
information listed in the files .plan
and .project in each
user's home directory. You can specify
each user either as a login name (exact match) or
as a first or last name (display information on all matching
names). Networked environments recognize arguments of the form
user@host and @host.
Options
- -l
Force long format (default): everything included by the
-s option and home directory, home phone, login shell,
mail status, .plan, .project, and .forward.
- -m
Suppress matching of users' "real" names.
- -p
Omit .plan and .project files from display.
- -s
Show short format: login name, real name, terminal name,
write status, idle time, office location, and office
phone number.
|
fingerd | in.fingerd [option] TCP/IP command. Remote user information server.
fingerd provides a network interface
to the finger program. It listens for
TCP connections on the finger port
and, for each connection, reads a single input line, passes the line
to finger, and copies the output of
finger to the user on the client
machine. fingerd is started by
inetd and must have an entry in
inetd's configuration file,
/etc/inetd.conf.
Option
- -w
Include additional information, such as uptime and the name of the
operating system.
|
flex | flex [options] [file] flex (Fast Lexical Analyzer Generator) is a faster variant of lex.
It generates a lexical analysis program (named lex.yy.c) based on the
regular expressions and C statements contained in one or more input
files. See also bison, yacc, and the O'Reilly book lex & yacc by John Levine, Tony Mason, and Doug Brown.
Options
- -b
Generate backup information to lex.backup.
- -d
Debug mode.
- -f
Use faster compilation (limited to small programs).
- -h
Help summary.
- -i
Scan case-insensitively.
- -l
Maximum lex compatibility.
- -o file
Write output to file instead of lex.yy.c.
- -p
Print performance report.
- -s
Exit if the scanner encounters input that does not match any of its rules.
- -t
Print to standard out. (By default, flex prints to lex.yy.c.)
- -v
Print a summary of statistics.
- -w
Suppress warning messages.
- -B
Generate batch (noninteractive) scanner.
- -F
Use the fast scanner table representation.
- -I
Generate an interactive scanner (default).
- -L
Suppress #line directives in lex.yy.c.
- -P prefix
Change default yy prefix to prefix for all globally visible
variable and function names.
- -V
Print version number.
- -7
Generate a 7-bit scanner.
- -8
Generate an 8-bit scanner (default).
- -+
Generate a C++ scanner class.
- -C
Compress scanner tables but do not use equivalence classes.
- -Ca
Align tables for memory access and computation. This creates
larger tables but gives faster performance.
- -Ce
Construct equivalence classes. This creates smaller tables and
sacrifices little performance (default).
- -Cf
Generate full scanner tables, not compressed.
- -CF
Generate faster scanner tables, like -F.
- -Cm
Construct metaequivalence classes (default).
- -Cr
Bypass use of the standard I/O library. Instead use read() system
calls.
|
fmt | fmt [options] [files] Convert text to specified width by filling lines and removing newlines.
Concatenate files on the command line, or read text from standard
input if - (or no file) is specified.
By default, preserve blank lines, spacing, and indentation.
fmt attempts to break lines at the end of sentences and to avoid
breaking lines after a sentence's first word or before its last.
Options
- -c, --crown-margin
Crown margin mode. Do not change each paragraph's first two lines'
indentation. Use the second
line's indentation as the default for
subsequent lines.
- -p prefix, --prefix=prefix
Format only lines beginning with prefix.
- -s, --split-only
Suppress line-joining.
- -t, --tagged-paragraph
Tagged paragraph mode. Same as crown mode when the indentation
of the first and second lines differs. If the indentation is the same,
treat the first line as its own separate paragraph.
- -u, --uniform-spacing
Print exactly one space between words and two between sentences.
- -w width, --width=width
Set output width to width. The default is 75.
- --help
Print help message and then exit.
- --version
Print version information and then exit.
|
fold | fold [option] [files] Break the lines of the named files so that they are no wider
than the specified width (default is 80).
fold breaks lines exactly at the
specified width,
even in the middle of a word.
Reads from standard input when given - as a file.
Options
- -b, --bytes
Count bytes, not columns (i.e., consider tabs, backspaces,
and carriage returns to be one column).
- -s, --spaces
Break at spaces only, if possible.
- -w, --width width
Set the maximum line width to width. Default is 80.
|
formail | formail [options] Filter standard input into mailbox format. If no sender is apparent,
provide the sender foo@bar. By default, escape bogus From lines
with >.
Options
- +skip
Do not split first skip messages.
- -total
Stop after splitting total messages.
- -a headerfield
Append headerfield to header, unless it already exists. If
headerfield is Message-ID or Resent-Message-ID with no contents,
generate a unique message ID.
- -b
Do not escape bogus From lines.
- -c
When header fields are more than one line long, concatenate the lines.
- -d
Do not assume that input must be in strict mailbox format.
- -e
Allow messages to begin one immediately after the other; do not require
empty space between them.
- -f
Do not edit non-mailbox-format lines. By default, formail prepends
From to such lines.
- -i headerfield
Append headerfield whether or not it already exists.
Rename each existing headerfield to Old-headerfield, unless
they are empty.
- -k
For use only with -r. Keep the body as well as the fields specified by -r.
- -m minfields
Require at least minfields before recognizing the beginning
of a new message. Default is 2.
- -n
Allow simultaneous formail processes to run.
- -p prefix
Escape lines with prefix instead of >.
- -q
Do not display write errors, duplicate messages, and mismatched
Content-Length fields. This is the default; use
-q- to turn it off.
- -r
Throw away all existing fields, retaining only X-Loop, and generate
autoreply header instead. You can preserve particular fields with
the -i option.
- -s
Must be the last option; everything following it will be
assumed to be its arguments. Divide input to separate mail messages, and pipe them to the
program specified or concatenate them to standard output (by
default).
- -t
Assume sender's return address to be valid. (By default, formail favors machine-generated addresses.)
- -u headerfield
Delete all but the first occurrence of headerfield.
- -x headerfield
Display the contents of headerfield on a single line.
- -z
When necessary, add a space between field names and contents.
Remove ("zap") empty fields.
- -A headerfield
Append headerfield whether or not it already exists.
- -B
Assume that input is in BABYL rmail format.
- -D maxlen idcache
Remember old message IDs (in idcache, which will grow no larger
than approximately maxlen). When splitting, refuse to output
duplicate messages. Otherwise, return true on discovering a duplicate.
With -r, look at the sender's mail address instead of the message ID.
- -I headerfield
Append headerfield whether or not it already exists.
Remove existing fields.
- -R oldfield newfield
Change all fields named oldfield to newfield.
- -U headerfield
Delete all but the last occurrence of headerfield.
- -Y
Format in traditional Berkeley style (i.e., ignore Content-Length
fields).
- -X headerfield
Display the field name and contents of headerfield on a single line.
|
free | free [options] Display statistics about memory usage: total free, used, physical,
swap, shared, and buffers used by the kernel.
Options
- -b
Calculate memory in bytes.
- -k
Default. Calculate memory in kilobytes.
- -m
Calculate memory in megabytes.
- -o
Do not display "buffer adjusted" line. The -o switch disables
the display "-/+ buffers" line.
- -s time
Check memory usage every time seconds.
- -t
Display all totals on one line at the bottom of output.
- -V
Display version information.
|
fsck | fsck [options] [filesystem] ... System administration command. Call the filesystem checker for the
appropriate system type, to check and repair filesystems. If a
filesystem is consistent, the number of files, number of blocks used,
and number of blocks free are reported. If a filesystem is
inconsistent, fsck prompts before
each correction is attempted. fsck's
exit code can be interpreted as the sum of all of those conditions
that apply:
- 1
Errors were found and corrected.
- 2
Reboot suggested.
- 4
Errors were found but not corrected.
- 8
fsck encountered an operational error.
- 16
fsck was called incorrectly.
- 128
A shared library error was detected.
Options
- --
Pass all subsequent options to filesystem-specific checker. All options that fsck doesn't recognize will also
be passed.
- -r
Interactive mode; prompt before making any repairs.
- -s
Serial mode.
- -t fstype
Specify the filesystem type. Do not check filesystems of any other
type.
- -A
Check all filesystems listed in /etc/fstab.
- -N
Suppress normal execution; just display what would be done.
- -R
Meaningful only with -A: check all filesystems listed in
/etc/fstab except the root filesystem.
- -T
Suppress printing of title.
- -V
Verbose mode.
|
fsck.minix | fsck.minix [options] device System administration command.
Similar to fsck, but specifically intended for Linux
MINIX filesystems.
Options
- -a
Automatic mode; repair without prompting.
- -f
Force checking, even if kernel has already marked the filesystem. fsck.minix will normally exit without
checking if the system appears to be clean.
- -l
List filesystems.
- -m
Enable MINIX-like "mode not cleared" warnings.
- -r
Interactive mode; prompt before making any repairs.
- -s
Display information about superblocks.
- -v
Verbose mode.
|
ftp | ftp [options] [hostname] Transfer files to and from remote network site hostname.
ftp prompts the user for a command. The commands are listed
after the options. Some of the commands are toggles, meaning
they turn on a feature when it is off and vice versa.
Options
- -d
Enable debugging.
- -g
Disable filename globbing.
- -i
Turn off interactive prompting.
- -n
No autologin upon initial connection.
- -v
Verbose. Show all responses from remote server.
Commands
- ![command [args]]
Invoke an interactive shell on the local machine. If arguments
are given, the first is taken as a command to execute directly,
with the rest of the arguments as that command's arguments.
- $ macro-name [args]
Execute the macro macro-name that was defined with the
macdef command. Arguments are passed to the macro unglobbed.
- account [passwd]
Supply a supplemental password that will be required by a remote system
for access to resources once a login has been successfully completed. If no argument is given, the user will be prompted for an account
password in a nonechoing mode.
- append local-file [remote-file]
Append a local file to a file on the remote machine. If remote-file
is not given, the local filename is used after being altered by
any ntrans or nmap setting. File transfer uses the current
settings for type, format, mode, and structure.
- ascii
Set the file transfer type to network ASCII (default).
- bell
Sound a bell after each file transfer command is completed.
- binary
Set file transfer type to support binary image transfer.
- bye
Terminate FTP session and then exit ftp.
- case
Toggle remote computer filename case mapping during mget. The default is
off. When case is on, files on the remote machine with
all-uppercase names will be copied to the local machine with
all-lowercase names.
- cd remote-directory
Change working directory on remote machine to remote-directory.
- cdup
Change working directory of remote machine to its parent directory.
- chmod [mode] [remote-file]
Change file permissions of remote-file. If options are omitted,
the command prompts for them.
- close
Terminate FTP session and return to command interpreter.
- cr
Toggle carriage return stripping during ASCII-type file retrieval.
- delete remote-file
Delete file remote-file on remote machine.
- debug [debug-value]
Toggle debugging mode. If debug-value is specified, it is used
to set the debugging level.
- dir [remote-directory] [local-file]
Print a listing of the contents in the directory
remote-directory, and, optionally, place the output
in local-file. If no directory is specified, the current
working directory on the remote machine is used. If no local file
is specified or - is given instead of the filename, output comes
to the terminal.
- disconnect
Synonym for close.
- form format
Set the file transfer form to format. Default format
is file.
- get remote-file [local-file]
Retrieve the remote-file and store it on the local machine.
If the local filename is not specified, it is given the same name
it has on the remote machine, subject to alteration by the
current case, ntrans, and nmap settings.
If local file is -, output comes to the terminal.
- glob
Toggle filename expansion for mdelete, mget, and
mput. If globbing is turned off, the filename arguments are
taken literally and not expanded.
- hash
Toggle hash-sign (#) printing for each data block transferred.
- help [command]
Print help information for command. With no argument, ftp
prints a list of commands.
- idle [seconds]
Get/set idle timer on remote machine. seconds specifies the length
of the idle timer; if omitted, the current idle timer is displayed.
- image
Same as binary.
- lcd [directory]
Change working directory on local machine. If directory is not
specified, the user's home directory is used.
- ls [remote-directory] [local-file]
Print listing of contents of directory on remote machine,
in a format chosen by the remote machine.
If remote-directory is not specified, current working directory
is used.
- macdef macro-name
Define a macro. Subsequent lines are stored as the macro
macro-name; a null line terminates macro input mode.
When $i is included in the macro, loop through arguments, substituting
the current argument
for $i on each pass. Escape $ with \.
- mdelete remote-files
Delete the remote-files on the remote machine.
- mdir remote-files local-file
Like dir, except multiple remote files may be specified.
- mget remote-files
Expand the wildcard expression remote-files on the remote machine
and do a get for each filename thus produced.
- mkdir directory-name
Make a directory on the remote machine.
- mls remote-files local-file
Like nlist, except multiple remote files may be specified, and
the local file must be specified.
- mode [mode-name]
Set file transfer mode to mode-name. Default mode is stream mode.
- modtime [file-name]
Show last modification time of the file on the remote machine.
- mput [local-files]
Expand wildcards in local-files given as arguments and
do a put for each file in the resulting list.
- newer remote-file [local-file]
Get file if remote file is newer than local file.
- nlist [remote-directory] [local-file]
Print list of files of a directory on the remote machine to local-file
(or the screen if local-file is not specified). If
remote-directory is unspecified, the current working
directory is used.
- nmap [inpattern outpattern]
Set or unset the filename mapping mechanism. The mapping follows the
pattern set by inpattern, a template for incoming filenames, and
outpattern, which determines the resulting mapped filename. The
sequences $1 through $9 are treated as variables, for example, the
inpattern $1.$2, along with the input file
readme.txt, would set $1 to readme and $2 to txt. An
outpattern of $1.data would result in an output file of
readme.data. $0 corresponds to the complete
filename. [string1, string2] is replaced by string1,
unless that string is null, in which case it's replaced by
string2.
- ntrans [inchars [outchars ]]
Set or unset the filename character translation mechanism. Characters
in a filename matching a character in inchars are replaced
with the corresponding character in outchars. If no arguments
are specified, the filename mapping mechanism is unset. If arguments
are specified:
Characters in remote filenames are translated during mput and
put commands issued without a specified remote target filename. Characters in local filenames are translated during mget and
get commands issued without a specified local target filename.
- open host [port]
Establish a connection to the specified host FTP server. An
optional port number may be supplied, in which case ftp will
attempt to contact an FTP server at that port.
- prompt
Toggle interactive prompting.
- proxy ftp-command
Execute an FTP command on a secondary control connection (i.e.,
send commands to two separate remote hosts simultaneously).
- put local-file [remote-file]
Store a local file on the remote machine. If remote-file is
left unspecified, the local filename is used after processing
according to any ntrans or nmap settings in naming the
remote file. File transfer uses the current settings for type,
file, structure, and transfer mode.
- pwd
Print name of the current working directory on the remote machine.
- quit
Synonym for bye.
- quote arg1 arg2...
Send the arguments specified, verbatim, to the remote FTP server.
- recv remote-file [local-file]
Synonym for get.
- reget remote-file [local-file]
Retrieve a file (like get), but restart at the end of
local-file. Useful for restarting a dropped transfer.
- remotehelp [command-name]
Request help from the remote FTP server. If command-name is
specified, remote help for that command is returned.
- remotestatus [filename]
Show status of the remote machine, or, if filename is specified,
filename on remote machine.
- rename [from] [to]
Rename file from on remote machine to to.
- reset
Clear reply queue.
- restart marker
Restart the transfer of a file from a particular byte count.
- rmdir [directory-name]
Delete a directory on the remote machine.
- runique
Toggle storing of files on the local system with unique filenames. When this option is on, rename files as .1 or .2, and soon, as appropriate,
to preserve unique filenames, and report each such action. Default value
is off.
- send local-file [remote-file]
Synonym for put.
- sendport
Toggle the use of PORT commands.
- site [command]
Get/set site-specific information from/on remote machine.
- size filename
Return size of filename on remote machine.
- status
Show current status of ftp.
- struct [struct-name]
Set the file transfer structure to struct-name.
By default, stream structure is used.
- sunique
Toggle storing of files on remote machine under unique filenames.
- system
Show type of operating system running on remote machine.
- tenex
Set file transfer type to that needed to talk to TENEX machines.
- trace
Toggle packet tracing.
- type [type-name]
Set file transfer type to type-name. If no type is specified,
the current type is printed. The default type is network ASCII.
- umask [mask]
Set user file-creation mode mask on the remote site. If mask
is omitted, the current value of the mask is printed.
- user username [password] [account]
Identify yourself to the remote FTP server.
ftp will prompt the user for the password, if not specified
and the server requires it, and the account field.
- verbose
Toggle verbose mode.
- ? [command]
Same as help.
|
ftpd | in.ftpd [options] TCP/IP command. Internet File Transfer Protocol server. The server uses
the TCP protocol and listens at the port specified in the
ftp service specification. ftpd is started by inetd and must
have an entry in inetd's configuration file, /etc/inetd.conf.
Options
- -d
Write debugging information to the syslog.
- -l
Log each FTP session in the syslog.
- -Tmaxtimeout
Set maximum timeout period in seconds. Default limit is 15 minutes.
- -ttimeout
Set timeout period to timeout seconds.
|
fuser | fuser [options] [files | filesystems] Identify processes that are using a file or filesystem. fuser outputs the process IDs of the processes
that are using the files or local
filesystems. Each process ID is followed by a
letter code: c if process is using
file as current directory, e if
executable, f if an open file,
m if a shared library, and r if the root directory. Any user with
permission to read /dev/kmem and
/dev/mem can use fuser, but only a privileged user can terminate
another user's process. fuser does
not work on remote (NFS) files.
If more than one group of files is specified, the options may be
respecified for each additional group of files. A lone dash (-)
cancels the options currently in force, and the new set of options
applies to the next group of files.
Options
- -
Return all options to defaults.
- -signal
Send signal instead of SIGKILL.
- -a
Display information on all specified files, even if they are not
being accessed by any processes.
- -i
Request user confirmation to kill a process. Ignored if
-k is not also specified.
- -k
Send SIGKILL signal to each process.
- -l
List signal names.
- -m
Expect files to exist on a mounted filesystem; include
all files accessing that filesystem.
- -s
Silent.
- -u
User login name, in parentheses, also follows process ID.
- -v
Verbose.
- -V
Display version information.
|
g++ | g++ [options] files Invoke gcc with the options necessary to make it recognize
C++. g++ recognizes all the file extensions gcc does, in
addition to C++ source files (.C, .cc, or .cxx
files) and C++ preprocessed files (.ii files). See also
gcc.
|
gated | gated [options] TCP/IP command. Gateway routing daemon.
gated handles multiple routing protocols
and replaces routed and any routing daemons that speak the Hello,
EGP, or BGP routing protocols. gated currently handles the RIP,
BGP, EGP, Hello, and
OSPF routing protocols and can be configured to perform
all or any combination of the five.
Options
- -c
Parse configuration file for syntax errors, then exit gated,
leaving a dump file in /usr/tmp/gated_dump.
- -f config_file
Use alternate configuration file, config_file. Default is
/etc/gated.conf.
- -n
Do not modify kernel's routing table.
- -t [trace_options]
Start gated with the specified tracing options enabled.
If no flags are specified, assume general.
The trace flags are:
- adv
Management of policy blocks.
- all
Includes normal, policy, route, state, task, and timer.
- general
Includes normal and route.
- iflist
The kernel interface list.
- normal
Normal protocols instances.
- parse
Lexical analyzer and parser.
- policy
Instances in which policy is applied to imported and exported routes.
- route
Any changes to routing table.
- state
State machine transitions.
- symbols
Symbols read from kernel -- note that they are read before the configuration
file is parsed, so this option must be specified on the command line.
- task
System tasks and interfaces.
- timer
Timer usage.
- -C
Parse configuration file for errors and set exit code to indicate
if there were any (1) or not (0), then exit.
- -N
Do not daemonize.
|
gawk | gawk [options] `script' [var=value...] [files] gawk [options] -f scriptfile [var=value...] [files] The GNU version of awk, a program that does pattern matching,
record processing, and other forms of text manipulation. For more
information, see Chapter 13, "The gawk Scripting Language".
|
gcc | gcc [options] files Compile one or more C source files (file.c),
assembler source files (file.s),
or preprocessed C source files (file.i). If the file suffix
is not recognizable, assume that the file is an object file
or library.
gcc automatically invokes the link editor ld
(unless -c, -S, or -E is supplied).
In some cases, gcc generates an object file
having a .o suffix and a corresponding root name.
By default, output is placed in a.out.
gcc accepts many system-specific options not covered here.
Note: gcc is the GNU form of cc; on most Linux systems,
the command cc will invoke gcc. The command
g++ will invoke gcc with the appropriate options
for interpreting C++.
Options
- -a
Provide profile information for basic blocks.
- -ansi
Enforce full ANSI conformance.
- -b machine
Compile for use on machine type.
- -c
Create linkable object file for each source file, but do not call
linker.
- -dD
Print #defines.
- -dM
Suppress normal output. Print series of #defines that are in
effect at the end of preprocessing.
- -dN
Print #defines with macro names only, not arguments or values.
- -fno-asm
Do not recognize asm, inline, or typeof as keywords.
Implied by -ansi.
- -fno-builtin
Do not recognize built-in functions unless they begin with two underscores.
- -fno-gnu-keywords
Do not recognize classof, headof, signature, sigof, or
typeof as keywords.
- -fno-ident
Do not respond to #ident commands.
- -fsigned-bitfields
- -funsigned-bitfields
- -fno-signed-bitfields
- -fno-unsigned-bitfields
Set default control of bitfields to signed or unsigned if not explicitly declared.
- -fsigned-char
Cause the type char to be signed.
- -fsyntax-only
Check for syntax errors. Do not attempt to actually compile.
- -funsigned-char
Cause the type char to be unsigned.
- -g
Include debugging information for use with gdb.
- -glevel
Provide level amount of debugging information. level
must be 1, 2, or 3, with 1 providing the least amount of information. The default is 2.
- -idirafter dir
Include dir in the list of directories to search when an
include file is not found in the normal include path.
- -include file
Process file before proceeding to the normal input file.
- -imacros file
Process the macros in file before proceeding to the normal
input file.
- -iprefix prefix
When adding directories with -iwithprefix, prepend
prefix to the directory's name.
- -isystem dir
Add dir to the list of directories to be searched when
a system file cannot be found in the main include path.
- -iwithprefix dir
Append dir to the list of directories to be searched when
a header file cannot be found in the main include path. If -iprefix has been set, prepend that prefix to the
directory's name.
- -llib
Link to lib.
- -nostartfiles
Force linker to ignore standard system startup files.
- -nostdinc
Search only specified, not standard, directories for header files.
- -nostdinc++
Suppress searching of directories believed to contain C++-specific
header files.
- -nostdlib
Suppress linking to standard library files.
- -o file
Specify output file as file. Default is a.out.
- -p
Provide profile information for use with prof.
- -pedantic
Warn verbosely.
- -pedantic-errors
Err in every case in which -pedantic would have produced
a warning.
- -pg
Provide profile information for use with gprof.
- -pipe
Transfer information between stages of compiler by pipes instead of
temporary files.
- -s
Remove all symbol table and relocation information from the
executable.
- -save-temps
Save temporary files in the current directory when compiling.
- -static
Suppress linking to shared libraries.
- -traditional
Attempt to behave like a traditional C compiler.
- -traditional-cpp
Cause the preprocessor to attempt to behave like a traditional
C preprocessor.
- -trigraphs
Include trigraph support.
- -u symbol
Force the linker to search libraries for a definition of symbol
and to link to them, if found.
- -undef
Define only those constants required by the language
standard, not system-specific constants like unix.
- -v
Verbose mode. Display commands as they are executed, gcc version
number, and preprocessor version number.
- -w
Suppress warnings.
- -x language
Expect input file to be written in language, which may be
c, objective-c, c-header, c++,
cpp-output, assembler, or assembler-with-cpp. If none is specified as language, guess the language
by filename extension.
- -Aquestion(answer)
If the preprocessor encounters a conditional such
as #if question, assert answer in response. To turn off standard assertions, use -A-.
- -Bpath
Specify the path directory in which the compiler files are located.
- -C
Retain comments during preprocessing. Meaningful only with -E.
- -Dname[=def]
Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has
lower precedence than -U.
- -E
Preprocess the source files, but do not compile. Print result to
standard output.
- -Idir
Include dir in list of directories to search for include files.
If dir is -, search those directories that were
specified by -I before the -I- only when
#include "file" is specified, not #include <file>.
- -Ldir
Search dir in addition to standard directories.
- -M
Instead of compiling, print a rule suitable for inclusion
in a makefile that describes dependencies of the source file
based on its #include directives. Implies -E.
- -MD
Similar to -M, but sends dependency information to files
ending in .d in addition to ordinary compilation.
- -MG
Used with -M or -MM. Suppress error messages
if an included file does not exist; useful if the included
file is automatically generated by a build.
- -MMD
Similar to -MD, but record only user header file information,
not system header file information.
- -MM
Similar to -M, but limit the rule to non-standard
#include files; that is, only files declared through
#include "file" and not those declared through
#include <file>.
- -H
Print pathnames of included files, one per line, on standard error.
- -O[level]
Optimize. level should be 1, 2, 3, or 0. The default is
1. 0 turns off optimization; 3 optimizes the most.
- -P
Preprocess input without producing line-control information used by
next pass of C compiler. Meaningful only with -E.
- -S
Compile source files into assembler code, but do not assemble.
- -Uname
Remove any initial definition of name, where name is a
reserved symbol predefined by the preprocessor or a name defined on a
-D option. Names predefined by cpp are unix and
i386.
- -V version
Attempt to run gcc version version.
- -W
Warn more verbosely than normal.
- -Wl,option
Invoke linker with option, which may be a comma-separated list.
- -Wa,option
Call assembler with option, which may be a comma-separated list.
- -Waggregate-return
Warn if any functions return structures or unions are defined or called.
- -Wall
Enable -W, -Wchar-subscripts, -Wcomment, -Wformat,
-Wimplicit, -Wparentheses, -Wreturn-type,
-Wswitch, -Wtemplate-debugging,
-Wtrigraphs,
-Wuninitialized, and -Wunused.
- -Wcast-align
Warn when encountering instances in which pointers are cast to types
that increase the required alignment of the target from its
original definition.
- -Wcast-qual
Warn when encountering instances in which pointers are cast to types
that lack the type qualifier with which the pointer was originally
defined.
- -Wchar-subscripts
Warn when encountering arrays with subscripts of type char.
- -Wcomment
Warn when encountering the beginning of a nested comment.
- -Wconversion
Warn in particular cases of type conversions.
- -Werror
Exit at the first error.
- -Wformat
Warn about inappropriately formatted printfs and scanfs.
- -Wimplicit
Warn when encountering implicit function or parameter declarations.
- -Winline
Warn about illegal inline functions.
- -Wmissing-declarations
Warn if a global function is defined without a previous declaration.
- -Wmissing-prototypes
Warn when encountering global function definitions without previous
prototype declarations.
- -Wnested-externs
Warn if an extern declaration is encountered within a function.
- -Wno-import
Don't warn about use of #import.
- -Wp,options
Pass options to the preprocessor. Multiple options are separated
by commas. Not a warning parameter.
- -Wparentheses
Enable more verbose warnings about omitted parentheses.
- -Wpointer-arith
Warn when encountering code that attempts to determine the size of
a function or void.
- -Wredundant-decls
Warn if anything is declared more than once in the same scope.
- -Wreturn-type
Warn about functions defined without return types or with improper
return types.
- -Wshadow
Warn when a local variable shadows another local
variable.
- -Wstrict-prototypes
Insist that argument types be specified in function declarations and
definitions.
- -Wswitch
Warn about switches that skip the index for one of their
enumerated types.
- -Wtemplate-debugging
Warn if debugging is not available for C++ templates.
- -Wtraditional
Warn when encountering code that produces different results in ANSI C
and traditional C.
- -Wtrigraphs
Warn when encountering trigraphs.
- -Wuninitialized
Warn when encountering uninitialized automatic
variables.
- -Wunused
Warn about unused variables and functions.
- -Xlinker option
Pass an option to the linker. A linker option with an argument
requires two -Xs, the first specifying the option and
the second specifying the argument.
Pragma directives
- #pragma interface [header-file]
Used in header files to force object files to provide
definition information via references, instead of including
it locally in each file. C++-specific.
- #pragma implementation [header-file]
Used in main input files to force generation of full output from
header-file (or, if it is not specified, from the header file
with the same base name as the file containing the pragma
directive). This information will be globally visible. Normally
the specified header file contains a #pragma interface
directive.
|
gdb | gdb [options] [program [core|pid]] GDB (GNU DeBugger) allows you to step through C, C++, and Modula-2
programs in order to find the point at which they break. The
program to be debugged is normally specified on the command line;
you can also specify a core or, if you want to investigate a
running program, a process ID.
Options
- -s file, -symbols=file
Consult file for symbol table. With -e, also uses file as
the executable.
- -e file, -exec=file
Use file as executable, to be read in conjunction with source code. May be used in conjunction with -s to read symbol table from the
executable.
- -c file, -core=file
Consult file for information provided by a core dump.
- -x file, -command=file
Read gdb commands from file.
- -d directory, -directory=directory
Include directory in path that is searched for source files.
- -n, -nx
Ignore .gdbinit file.
- -q, -quiet
Suppress introductory and copyright messages.
- -batch
Exit after executing all the commands specified in .gdbinit
and -x files. Print no startup messages.
- -cd=directory
Use directory as gdb's working directory.
- -f, -fullname
Show full filename and line number for each stack frame.
- -b bps
Set line speed of serial device used by GDB to bps.
- -tty=device
Set standard in and standard out to device.
Common commands
These are just some of the more common gdb commands; there are
too many commands to list all of them here:
- bt
Print the current location within the program and a
stack trace showing how the current location was reached.
(where does the same thing.)
- break
Set a breakpoint in the program.
- cd
Change the current working directory.
- clear
Delete the breakpoint where you just stopped.
- commands
List commands to be executed when breakpoint is hit.
- c
Continue execution from a breakpoint.
- delete
Delete a breakpoint or a watchpoint; also used in
conjunction with other commands.
- display
Cause variables or expressions to be displayed when program stops.
- down
Move down one stack frame to make another function the current one.
- frame
Select a frame for the next continue command.
- info
Show a variety of information about the program. For
instance, info breakpoints shows all outstanding
breakpoints and watchpoints.
- jump
Start execution at another point in the source file.
- kill
Abort the process running under gdb's control.
- list
List the contents of the source file corresponding to
the program being executed.
- next
Execute the next source line, executing a function in its entirety.
- print
Print the value of a variable or expression.
- pwd
Show the current working directory.
- ptype
Show the contents of a datatype, such as a structure or C++ class.
- quit
Exit gdb.
- reverse-search
Search backward for a regular expression in the source file.
- run
Execute the program.
- search
Search for a regular expression in the source file.
- set variable
Assign a value to a variable.
- signal
Send a signal to the running process.
- step
Execute the next source line, stepping into a
function if necessary.
- undisplay
Reverse the effect of the display command; keep expressions from
being displayed.
- until
Finish the current loop.
- up
Move up one stack frame to make another function the current one.
- watch
Set a watchpoint (i.e., a data breakpoint) in the
program.
- whatis
Print the type of a variable or function.
|
gdc | gdc [options] command TCP/IP command. Administer gated. Various commands start
and stop the daemon, send signals to it, maintain the configuration
files, and manage state and core dumps.
Options
- -c size
Specify maximum core dump size.
- -f size
Specify maximum file dump size.
- -m size
Specify maximum data segment size.
- -n
Suppress editing of the kernel forwarding table.
- -q
Quiet mode: suppress warnings and log errors to
syslogd instead of standard
error.
- -s size
Specify maximum stack size.
- -t seconds
Wait seconds seconds (default is 10) for gated to complete specified
operations at start and stop time.
Commands
- BACKOUT
Restore /etc/gated.conf from /etc/gated.conf-, whether or not
the latter exists.
- backout
Restore /etc/gated.conf from /etc/gated.conf-, assuming the latter
exists.
- checkconf
Report any syntax errors in /etc/gated.conf.
- checknew
Report any syntax errors in /etc/gated.conf+.
- COREDUMP
Force gated to core dump and exit.
- createconf
Create an empty /etc/gated.conf+ if one does not already exist, and
set it to mode 664, owner root, group gdmaint.
- dump
Force gated to dump to /usr/tmp/gated_dump and then continue
normal operation.
- interface
Reload interface configuration.
- KILL
Terminate immediately (ungracefully).
- modeconf
Set all configuration files to mode 664, owner root, group gdmaint.
- newconf
Make sure that /etc/gated.conf+ exists and move it to
/etc/gated.conf. Save the old /etc/gated.conf as /etc/gated.conf-.
- reconfig
Reload configuration file.
- restart
Stop and restart gated.
- rmcore
Remove any gated core files.
- rmdmp
Remove any gated state dump files.
- rmparse
Remove any gated files that report on parse errors. These are generated
by the checkconf and checknew commands.
- running
Exit with zero status if gated is running and nonzero if it is not.
- start
Start gated, unless it is already running, in which case return an error.
- stop
Stop gated as gracefully as possible.
- term
Terminate gracefully.
- toggletrace
Toggle tracing.
Files
- /etc/gcd.conf+
The test configuration file. Once you're satisfied that it works, you
should run gated newconf to install it as
/etc/gated.conf.
- /etc/gated.conf-
A backup of the old configuration file.
- /etc/gated.conf--
A backup of the backup of the old configuration file.
- /etc/gated.conf
The actual configuration file.
- /etc/gated.pid
gated's process ID.
- /usr/tmp/gated_dump
The state dump file.
- /usr/tmp/gated_parse
A list of the parse errors generated by reading the configuration file.
|
getkeycodes | getkeycodes Print the kernel's scancode-to-keycode mapping table.
|
getty | getty [options] port [speed [term [lined]]] System administration command.
Set terminal type, modes, speed, and line discipline. Linux systems
may use agetty instead, which uses a different syntax. getty
is invoked by init. It is the second process in the series
init-getty-login-shell, which ultimately connects a user with
the Linux system. getty reads the user's login name and invokes
the login command with the user's name as an argument. While
reading the name, getty attempts to adapt the system
to the speed and type of device being used.
You must specify a port argument, which getty will use to
attach itself to the device /dev/port.
getty will then scan the defaults file,
usually /etc/default/getty, for runtime values and parameters.
These may also be specified, for the most part, on the command line,
but the values in the defaults file take precedence. The speed
argument is used to point to an entry in the file /etc/gettydefs,
which contains the initial baud rate, tty settings, and login prompt
and final speed and settings for the connection. The first entry is the default in /etc/gettydefs. term specifies the
type of terminal, with lined the optional line discipline
to use.
Options
- -c file
Check the gettydefs file. file is the name of the gettydefs
file. Produces the files' values and reports parsing errors to standard
output.
- -d file
Use a different default file.
- -h
Do not force a hangup on the port when initializing.
- -r delay
Wait for single character from port, then wait delay seconds
before proceeding.
- -t timeout
If no username is accepted within timeout seconds, close connection.
- -w string
Wait for string characters from port before proceeding.
|
gprof | gprof [options] [object_file] Display the profile data for an object file.
The file's symbol table is compared with the call graph profile
file gmon.out
(previously created by compiling with gcc -pg).
Options
- -a
Do not display statically declared functions. Since their information
might still be relevant, append it to the information about the
functions loaded immediately before.
- -b
Do not display information about each field in the profile.
- -c
Consult the object file's text area to attempt to determine the
program's static call graph. Display static-only parents and
children with call counts of 0.
- -e routine
Do not display entries for routine and its descendants.
- -f routine
Print only routine, but include time spent in all
routines.
- -k from to
Remove arcs between the routines from and to.
- -s
Summarize profile information in the file gmon.sum.
- -v
Print version and exit.
- -z
Include zero-usage calls.
- -E routine
Do not display entries for routine and its descendants or
include time spent on them in calculations for total time.
- -F routine
Print only information about routine. Do not include time spent
in other routines.
|
grep | grep [options] pattern [files] Search one or more files for lines that match a
regular expression pattern. Regular expressions are described
in Chapter 9, "Pattern Matching".
Exit status is 0 if any lines match, 1 if none match, and 2 for errors.
See also egrep and fgrep.
Options
- -a, --text
Don't suppress output lines with binary data; treat as text.
- -b, --byte-offset
Print the byte offset within the input file before
each line of output.
- -b, --byte-offset
Print the byte offset within the input file before
each line of output.
- -c, --count
Print only a count of matched lines. With -v or --revert-match option,
count nonmatching lines.
- -d action, --directories=action
Define an action for processing directories. Possible
actions are:
- read
Read directories like ordinary files (default).
- skip
Skip directories.
- recurse
Recursively read all files under each directory. Same as
-r.
- -e pattern, --regexp=pattern
Search for pattern. Same as specifying
a pattern as an argument, but useful in protecting patterns
beginning with -.
- -f file, --file=file
Take a list of patterns from file, one per line.
- -h, --no-filename
Print matched lines but not filenames
(inverse of -l).
- -i, --ignore-case
Ignore uppercase and lowercase distinctions.
- -l, --files-with-matches
List the names of files with matches but not individual
matched lines; scanning per file stops on the first match.
- -n, --line-number
Print lines and their line numbers.
- -q, --quiet, --silent
Suppress normal output in favor of quiet mode;
the scanning stops on the first match.
- -r, --recursive
Recursively read all files under each directory. Same as
-d recurse.
- -s, --no-messages
Suppress error messages about nonexistent or unreadable files.
- -v, --revert-match
Print all lines that don't match
pattern.
- -w, --word-regexp
Match on whole words only. Words are divided by characters that
are not letters, digits, or underscores.
- -x, --line-regexp
Print lines only if pattern matches the entire line.
- -A num, --after-context=num
Print num lines of text that occur after
the matching line.
- -B num, --before-context=num
Print num lines of text that occur before
the matching line.
- -C[num], --context=[num], -num
Print num lines of leading and trailing context. Default context is 2 lines.
- -L, --files-without-match
List files that contain no matching lines.
- -V, --version
Print the version number and then exit.
Examples
List the number of users who use tcsh:
grep -c /bin/tcsh /etc/passwd
List header files that have at least one #include directive:
grep -l '^#include' /usr/include/*
List files that don't contain pattern:
grep -c pattern files | grep :0
|
groff | groff [options] [files] troff [options] [files] Frontend to the groff document-formatting system,
which normally runs troff along with a postprocessor
appropriate for the selected output device. Options without
arguments can be grouped after a single dash (-).
A filename of - denotes standard input.
Options
- -a
Generate an ASCII approximation of the typeset output.
- -b
Print a backtrace.
- -C
Enable compatibility mode.
- -dcs, -dname=s
Define the character c or string name to be
the string s.
- -e
Preprocess with eqn.
- -E
Don't print any error messages.
- -ffam
Use fam as the default font family.
- -Fdir
Search dir for subdirectories with DESC
and font files
before the default /usr/lib/groff/font.
- -h
Print a help message.
- -i
Read standard input after all files have
been processed.
- -l
Send the output to a printer (as specified
by the print command in the device description file).
- -Larg
Pass arg to the spooler. Each argument should be
passed with a separate -L option.
- -mname
Read the macro file tmac.name.
- -Mdir
Search directory dir for macro files before the default
directory /usr/lib/groff/tmac.
- -nnum
Set the first page number to num.
- -N
Don't allow newlines with eqn delimiters; equivalent
to eqn's -N option.
- -olist
Output only pages specified in list, which is a comma-separated
list of page ranges.
- -p
Preprocess with pic.
- -Parg
Pass arg to the postprocessor. Each argument
should be passed with a separate -P option.
- -rcn, -name=n
Set the number register c or name to
n. c is a single character and
n is any troff
numeric expression.
- -R
Preprocess with refer.
- -s
Preprocess with soelim.
- -S
Use safer mode (i.e., pass the -S option to pic and use
the -msafer macros with troff).
- -t
Preprocess with tbl.
- -Tdev
Prepare output for device dev; the default
is ps.
- -v
Make programs run by groff print
out their version number.
- -V
Print the pipeline on stdout instead of executing it.
- -wname
Enable warning name. You can specify multiple
-w options. See the troff manpage
for a list of warnings.
- -Wname
Disable warning name. You can specify multiple
-W options. See the troff manpage
for a list of warnings.
- -z
Suppress troff output (except error messages).
- -Z
Do not postprocess troff output. Normally groff automatically runs the appropriate postprocessor.
Devices
- ascii
Typewriter-like device
- dvi
TeX dvi format
- latin1
Typewriter-like devices using the ISO Latin-1
character set
- ps
PostScript
- X75
75-dpi X11 previewer
- X100
100-dpi X11 previewer
- lj4
HP LaserJet4-compatible (or other PCL5-compatible) printer
Environment variables
- GROFF_COMMAND_PREFIX
If set to be X, groff will
run Xtroff instead
of troff.
- GROFF_FONT_PATH
Colon-separated list of directories in which to search
for the devname directory.
- GROFF_TMAC_PATH
Colon-separated list of directories in which to search
for the macro files.
- GROFF_TMPDIR
If set, temporary files will be created in this directory;
otherwise, they will be created in TMPDIR (if set) or
/tmp (if TMPDIR is not set).
- GROFF_TYPESETTER
Default device.
- PATH
Search path for commands that groff executes.
|
groupadd |
groupadd [options] group System administration command. Create new group account
group.
Options
- -ggid
Assign numerical group ID. (By default, the first available number
above 500 is used.) The value must be unique unless the -o
option is used.
- -o
Accept a nonunique gid with the -g option.
|
groupdel |
groupdel group System administration command. Remove group from
system account files. You may still need to find and change
permissions on files that belong to the removed group.
|
groupmod | groupmod [options] group System administration command.
Modify group information for group.
Options
- -g gid
Change the numerical value of the group ID. Any files
that have the old gid will have to be
changed manually. The new gid must be unique
unless the -o option is used.
- -n name
Change the group name to name.
- -o
Override. Accept a nonunique gid.
|
groups | groups [options] [users] Show the groups that each user belongs to (default
user is the owner of the current group).
Groups are listed in /etc/passwd and
/etc/group.
Options
- --help
Print help message.
- --version
Print version information.
|
grpck | grpck [option] [files] System administration command. Remove corrupt or duplicate entries in
the /etc/group and
/etc/gshadow files. Generate warnings for other
errors found. grpck will prompt for
a "yes" or "no" before deleting entries. If the user replies "no,"
the program will exit. If run in a noninteractive mode, the reply to
all prompts is "no." Alternate group and gshadow
files can be checked. If other errors are found,
the user will be encouraged to run the groupmod command.
Option
- -n
Noninteractive mode.
Exit codes
- 0
Success.
- 1
Syntax error.
- 2
One or more bad group entries found.
- 3
Could not open group files.
- 4
Could not lock group files.
- 5
Could not write group files.
|
grpconv |
grpconv grpunconv System administration command. Like pwconv, the grpconv command creates a shadowed group file
to keep your encrypted group passwords safe from password cracking
programs. grpconv creates the
/etc/gshadow file based on your existing
/etc/groups file and replaces your encrypted
password entries with x. If you add
new entries to the /etc/groups file, you can run
grpconv again to transfer the new
information to /etc/gshadow. It will ignore
entries that already have a password of x and convert those that do not. grpunconv restores the encrypted passwords to
your /etc/groups file and removes the
/etc/gshadow file.
|
gs | gs [options] [files]
An interpreter for Adobe Systems' PostScript and PDF (Portable
Document Format) languages; used for document processing. With -
in place of files, standard input is used.
Options
- -- filename arg1 ...
Take the next argument as a filename, but use all remaining
arguments to define ARGUMENTS in userdict (not systemdict) as
an array of those strings, before running the file.
- -gnumber1xnumber2
Specify width and height of device; intended for systems
like the X Window System.
- -q
Quiet startup.
- -rnumber, -rnumber1xnumber2
Specify X and Y resolutions (for the benefit
of devices, such as printers, that support multiple
X and Y resolutions). If only one number is given,
it is used for both X and Y resolutions.
- -Dname=token, -dname=token
Define a name in systemdict with the given definition.
The token must be exactly one token (as defined by the
token operator) and must not contain any
whitespace.
- -Dname, -dname
Define a name in systemdict with a null value.
- -Idirectories
Adds the designated list of directories at the head
of the search path for library files.
- -Sname=string, -sname=string
Define a name in systemdict with a given string as
value.
Special names
- -dDISKFONTS
Causes individual character outlines to be loaded
from the disk the first time they are encountered.
- -dNOBIND
Disables the bind operator. Useful only for debugging.
- -dNOCACHE
Disables character caching. Useful only for debugging.
- -dNODISPLAY
Suppresses the normal initialization of the output
device. May be useful when debugging.
- -dNOPAUSE
Disables the prompt and pause at the end of each page.
- -dNOPLATFONTS
Disables the use of fonts supplied by the underlying
platform (e.g., the X Window System).
- -dSAFER
Disables the deletefile and renamefile operators
and the ability to open files in any mode other
than read-only.
- -dWRITESYSTEMDICT
Leaves systemdict writable.
- -sDEVICE=device
Selects an alternate initial output device.
- -sOUTPUTFILE=filename
Selects an alternate output file (or pipe) for the
initial output device.
|
gunzip | gunzip [options] [files] Uncompress files compressed by gzip.
See gzip for a list of options.
|
gzexe | gzexe [option] [files] Compress executables. When run, these files automatically uncompress, thus
trading time for space. gzexe creates backup
files (filename~), which
should be removed after testing the original.
Option
- -d
Decompress files.
|
gzip | gzip [options] [files] gunzip [options] [files] zcat [options] [files]
Compress specified files (or read from standard input) with Lempel-Ziv
coding (LZ77). Rename compressed file to
filename.gz; keep ownership modes and
access/modification times. Ignore symbolic links. Uncompress with
gunzip, which takes all of gzip's options, except those specified.
zcat is identical to gunzip -c and takes the options
-fhLV, described here. Files
compressed with the compress command
can be decompressed using these commands.
Options
- -n, --fast, --best
Regulate the speed of compression using the specified digit
n, where -1 or
--fast indicates the
fastest compression method (less compression) and
-9 or
--best indicates the
slowest compression method (most compression). The default compression
level is -6.
- -a, --ascii
ASCII text mode: convert end-of-lines using local
conventions. This option is supported only on some
non-Unix systems.
- -c, --stdout, --to-stdout
Print output to standard output, and do not change input files.
- -d, --decompress, --uncompress
Same as gunzip.
- -f, --force
Force compression. gzip would normally
prompt for permission to continue when the file has multiple
links, its .gz version already exists, or
it is reading compressed data to or from a terminal.
- -h --help
Display a help screen and then exit.
- -l, --list
Expects to be given compressed files as arguments. Files may be
compressed by any of the following methods: gzip, deflate, compress, lzh,
and pack. For each file, list
uncompressed and compressed sizes (the latter being always -1
for files compressed by programs other than gzip), compression ratio,
and uncompressed name. With -v, also print compression method,
the 32-bit CRC of the uncompressed data, and the
timestamp.
With
-N, look inside the file for the uncompressed name and timestamp.
- -L, --license
Display the gzip license and quit.
- -n, --no-name
When compressing, do not save the original filename
and timestamp by default. When decompressing,
do not restore the original filename if present,
and do not restore the original timestamp if present.
This option is the default when decompressing.
- -N, --name
Default. Save original name and timestamp. When decompressing,
restore original name and timestamp.
- -q, --quiet
Print no warnings.
- -r, --recursive
When given a directory as an argument, recursively compress or
decompress files within it.
- -S suffix, --suffix suffix
Append .suffix. Default is
gz. A null suffix while
decompressing causes gunzip to attempt
to decompress all specified files, regardless of suffix.
- -t, --test
Test compressed file integrity.
- -v, --verbose
Print name and percent size reduction for each file.
- -V, --version
Display the version number and compilation options.
|
halt | halt [options] System administration command.
Insert a note in the file /var/log/wtmp; if the system is
in runlevel 0 or 6, stop all processes; otherwise, call
shutdown -nf.
Options
- -d
Suppress writing to /var/log/wtmp.
- -f
Call halt even when shutdown -nf would normally be
called (i.e., force a call to halt, even when not in runlevel 0
or 6).
- -n
Suppress normal call to sync.
- -w
Suppress normal execution; simply write to /var/log/wtmp.
|
head | head [options] [files] Print the first few lines (default is 10) of one or more
files.
If files is missing or -, read from standard
input. With more than one file, print a header for each file.
Options
- -c num[bkm], --bytes num
Print first num bytes or, if
num is followed by b,
k, or
m, first num
512-byte blocks, 1-kilobyte blocks, or 1-megabyte blocks.
- --help
Display help and then exit.
- -n num, --lines num, -num
Print first num lines. Default is 10.
- -q, --quiet, --silent
Quiet mode; never print headers giving filenames.
- -v, --verbose
Print filename headers, even for only one file.
- --version
Output version information and then exit.
Examples
Display the first 20 lines of phone_list:
head -20 phone_list
Display the first 10 phone numbers having a 202 area code:
grep '(202)' phone_list | head
|
host | host [options] host [server] host [options] zone [server]
System administration command.
Print information about specified hosts or zones in DNS. Hosts may be IP
addresses or hostnames; host converts IP addresses to hostnames
by default and appends the local domain to hosts without a
trailing dot. Default servers are determined in /etc/resolv.conf.
For more information about hosts and zones, try Chapters 1 and 2 of
DNS and BIND by Paul Albitz and Cricket Liu,
published by O'Reilly & Associates.
Options
- -a
Same as -t ANY.
- -c class
Search for specified resource record class (IN, INTERNET, CS,
CSNET, CH, CHAOS, HS, HESIOD, ANY, or *). Default is IN.
- -d
Debugging mode. -dd is a more verbose version.
- -e
Do not print information about domains outside of specified zone.
For hostname queries, do not print "additional information" or
"authoritative nameserver."
- -f file
Output to file as well as standard out.
- -i
Given an IP address, return the corresponding in-addr.arpa
address, class (always PTR), and hostname.
- -l zone
List all machines in zone.
- -m
Print only MR, MG, and MB records; recursively expand MR (renamed
mail box) and MG (mail group) records to MB (mail box) records.
- -o
Do not print output to standard out.
- -p [server]
For use with -l. Query only the zone's primary nameserver (or
server) for zone transfers, instead of those authoritative
servers that respond. Useful for testing unregistered zones.
- -q
Quiet. Suppress warning, but not error, messages.
- -r
Do not ask contacted server to query other servers, but require only
the information that it has cached.
- -t type
Look for type entries in the resource record.
type may be A, NS, PTR, ANY, or * (all).
- -u
Use TCP, not UDP.
- -v
Verbose. Include all fields from resource record, even
time-to-live and class, as well as
"additional information" and "authoritative nameservers" (provided by
the remote nameserver).
- -vv
Very verbose. Include information about host's defaults.
- -w
Never give up on queried server.
- -x
Allow multiple hosts or zones to be specified. If a server is also
specified, the argument must be preceded by -X.
- -A
For hostnames, look up the associated IP address, and then reverse look up
the hostname, to see if a match occurs.
For IP addresses, look up the associated hostname, and determine whether
the host recognizes that address as its own. For zones, check IP addresses for all hosts. Exit silently if no incongruities are discovered.
- -C
Similar to -l, but also check to see if the zone's name servers
are really authoritative. The zone's SOA (start of authority) records
specify authoritative name servers (in NS fields). Those servers
are queried; if they do not have SOA records, host reports
a lame delegation. Other checks are made as well.
- -D
Similar to -H but include the names of hosts with more
than one address per defined name.
- -E
Similar to -H but do not treat extra-zone hosts as errors.
Extra-zone hosts are hosts in an undefined subdomain.
- -F file
Redirect standard out to file, and print extra resource record
output only on standard out.
- -G zone
Similar to -H but include the names of gateway hosts.
- -H zone
Print the number of unique hosts within zone. Do not
include aliases. Also list all errors found (extra-zone names,
duplicate hosts).
- -I chars
Do not print warnings about domain names containing illegal characters
chars, such as _.
- -L level
For use with -l. List all delegated zones within this zone,
up to level deep, recursively.
- -P servers
For use with -l. servers should be a comma-separated list. Specify preferred hosts for secondary servers to use when copying
over zone data. Highest priority is given to those servers that match
the most domain components in a given part of servers.
- -R
Treat non-fully-qualified hostnames as BIND does, searching each
component of the local domain.
- -S
For use with -l. Print all hosts within the zone to standard
out. Do not print hosts within subzones. Include
class and IP address. Print warning messages (illegal names,
lame delegations, missing records, etc.) to standard error.
- -T
Print time-to-live values (how long information about each host
will remain cached before the nameserver refreshes it).
- -X server
Specify a server to query, and allow multiple hosts or zones to be
specified.
- -Z
When printing recource records, include trailing dot in
domain names, and print time-to-live value and class name.
|
hostid | hostid Print the ID number in hexadecimal of the current host.
|
hostname | hostname [option] [nameofhost] Set or print name of current host system. A privileged user can set
the hostname with the nameofhost argument.
Option
- -a, --alias
Display the alias name of the host (if used).
- -d, --domain
Print DNS domain name.
- -f, --fqdn, --long
Print fully qualified domain name.
- -F file, --file file
Consult file for hostname.
- -h, --help
Print a help message and then exit.
- -i, --ip-address
Display the IP address(es) of the host.
- -s, --short
Trim domain information from the printed name.
- -v, --verbose
Verbose mode.
- -V, --version
Print version information and then exit.
- -y, --yp, --nis
Display the NIS domain name. A privileged user can set a new NIS domain
name with nameofhost.
|
hwclock | hwclock [options] System administration command.
Read or set the hardware clock. This command maintains
change information in /etc/adjtime, which can be
used to adjust the clock based on how
much it drifts over time. hwclock replaces
the clock command. The single-letter options
are included for compatibility with the older command.
Options
You may specify only one of the following options:
- -a
Adjust the hardware clock based on information in /etc/adjtime
and set the system clock to the new time.
- --adjust
Adjust the hardware clock based on information in /etc/adjtime.
- --date date
Meaningful only with the --set option. date is
a string appropriate for use with the date command.
- --debug
Print information about what hwclock is doing.
- -r, --show
Print the current time stored in the hardware clock.
- -s, --hctosys
Set the system time in accordance with the hardware clock.
- --set
Set the hardware clock according to the time given in the --date
parameter.
- --test
Do not actually change anything. This is good for checking
syntax.
- -u, --utc
The hardware clock is stored in Universal Coordinated Time.
- --version
Print version and exit.
- -w, --systohc
Set the hardware clock in accordance with the system time.
|
icmpinfo | icmpinfo [options] TCP/IP command. Intercept and interpret ICMP
packets. Print the address and name of the message's sender, the
source port, the destination port, the sequence, and the packet
size. By default, provide information only about packets that are
behaving oddly.
Options
- -k
Kill the syslogd process begun by -l.
- -l
Record via syslogd. Only a privileged user may use this option.
- -n
Use IP addresses instead of hostnames.
- -p
Suppress decoding of port number: do not attempt to guess the name
of the service that is listening at that port.
- -s
Include IP address of interface that received the packet, in case
there are several interfaces on the host machine.
- -v
Verbose. Include information about normal ICMP packets. You may also specify -vv and -vvv for extra
verbosity.
|
id | id [options] [username] Display information about yourself or another user: user ID,
group ID, effective user ID and group ID if relevant, and additional
group IDs.
Options
- -g, --group
Print group ID only.
- -G, --groups
Print supplementary groups only.
- -n, --name
With -u, -g, or -G, print user or group name, not number.
- -r, --real
With -u, -g, or -G, print real, not effective, user ID or
group ID.
- -u, --user
Print user ID only.
- --help
Print help message and then exit.
- --version
Print version information.
|
identd | in.identd [options] [kernelfile [kmemfile]] TCP/IP command. Provide the name of the user whose process is running
a specified TCP/IP connection. You may specify the kernel and its
memory space.
Options
- -a ip_address
Bind to ip_address. Useful only with -b. By default, bind to the INADDR_ANY address.
- -b
Run standalone; not for use with inetd.
- -d
Allow debugging requests.
- -ggid
Attempt to run in the group gid. Useful only with -b.
- -i
Run as a daemon, one process per request.
- -l
Log via syslogd.
- -m
Allow multiple requests per session.
- -n
Return user IDs instead of usernames.
- -N
Do not provide a user's name or user ID if the file .noident
exists in the user's home directory.
- -o
When queried for the type of operating system, always return
OTHER.
- -pport
Listen at port instead of the default, port 113.
- -tseconds
Exit if no new requests have been received before seconds
seconds have passed. Note that, with -i or -w, the next
new request will result in identd being restarted. Default is
infinity (never exit).
- -uuid
Attempt to run as uid. Useful only with -b.
- -V
Print version and exit.
- -w
Run as a daemon, one process for all requests.
|
ifconfig | ifconfig [interface] ifconfig [interface address_family parameters addresses] TCP/IP command. Assign an address
to a network interface and/or configure network
interface parameters. ifconfig is typically used at boot time to define
the network address of each interface on a machine. It may
be used at a later time to redefine an interface's address or
other parameters. Without arguments, ifconfig
displays the current configuration for a network interface. Used
with a single interface argument, ifconfig displays that particular interface's current configuration.
Arguments
- interface
String of the form name unit, for example, en0.
- address_family
Since an interface may receive transmissions in differing protocols,
each of which may require separate naming schemes, you can specify the address_family to change the interpretation
of the remaining parameters. You may
specify inet (the default; for TCP/IP), ax25 (AX.25 Packet Radio),
ddp (Appletalk Phase 2), or ipx (Novell).
- Parameters
The following parameters may be set with ifconfig:
- allmulti/-allmulti
Enable/disable sending of incoming frames to the kernel's
network layer.
- arp/-arp
Enable/disable use of the Address Resolution Protocol in mapping between
network-level addresses and link-level addresses.
- broadcast
(inet only.) Specify address to use to represent broadcasts
to the network. Default is the address with a host part of all 1s (i.e.,
x.y.z.255 for a class C network).
- debug/-debug
Enable/disable driver-dependent debugging code.
- dest_address
Specify the address of the correspondent on the other end of
a point-to-point link.
- down
Mark an interface "down" (unresponsive).
- hw class address
Set the interface's hardware class and address. class may be
ether (Ethernet), ax25 (AX.25 Packet Radio), or
ARCnet.
- irq addr
Set the device's interrupt line.
- metric n
Set routing metric of the interface to n. Default is 0.
- mtu num
Set the interface's Maximum Transfer Unit (MTU).
- multicast
Set the multicast flag.
- netmask mask
(inet only.) Specify how much of the address to reserve for subdividing
networks into subnetworks. mask can be specified as a single
hexadecimal number with a leading 0x, with a dot notation Internet address,
or with a pseudonetwork name listed in the network table /etc/networks.
- pointopoint/-pointopoint [address]
Enable/disable point-to-point interfacing, so that the connection
between the two machines is dedicated.
- up
Mark an interface "up" (ready to send and receive).
- trailers/-trailers
Request/disable use of a "trailer" link-level encapsulation when sending.
- address
Either a hostname present in the hostname database (/etc/hosts),
or an Internet address expressed in the Internet standard dot
notation.
|
imake | imake options C preprocessor (cpp) interface to the
make utility. imake (for include make)
solves the portability problem of make by allowing machine dependencies to be
kept in a central set of configuration files, separate from the
descriptions of the various items to be built. The targets are
contained in the Imakefile, a machine-independent
description of the targets to be built, written as cpp macros. imake uses cpp
to process the configuration files and the
Imakefile, and to generate machine-specific
Makefiles, which can then be used by
make.
One of the configuration files is a template file, a master file for
imake. This template file (default is
Imake.tmpl) #includes the other configuration files that
contain machine dependencies such as variable assignments, site
definitions, and cpp macros, and
directs the order in which the files are processed. Each file affects
the interpretation of later files and sections of
Imake.tmpl. Comments may be included in
imake configuration files, but the
initial # needs to be preceded with
an empty C comment:
/**/#
For more information, see cpp and
make. Also check out the Nutshell
Handbook Software Portability with imake, by Paul
DuBois.
Options
- -Ddefine
Set directory-specific variables. This option is passed directly to
cpp.
- -e
Execute the generated Makefile. Default is to leave this to the
user.
- -f filename
Name of per-directory input file. Default is
Imakefile.
- -Idirectory
Directory in which imake template and configuration files may
be found. This option is passed directly to cpp.
- -s filename
Name of make description file to be generated. If
filename is a -- , the output is written to stdout. The default is to
generate, but not execute, a Makefile.
- -Ttemplate
Name of master template file used by cpp. This file is
usually located in the directory specified with the -I option. The default file is Imake.tmpl.
- -v
Print the cpp command line used to generate the Makefile.
Tools
Following is a list of tools used with imake:
- makedepend [options] files
Create header file dependencies in Makefiles. make- depend
reads the named input source files in sequence and parses them
to process #include, #define, #undef, #ifdef,
#ifndef, #endif, #if, and #else directives
so it can tell which #include directives would be used in a
compilation. makedepend determines the dependencies and writes
them to the Makefile. make then knows which object files must
be recompiled when a dependency has changed. makedepend has the
following options:
- -- options --
Ignore any unrecognized options following a double hyphen. A second
double hyphen terminates this action. Recognized options between
the hyphens are processed normally.
- -a
Append dependencies to any existing ones instead of replacing existing ones.
- -ffilename
Write dependencies to filename instead of to Makefile.
- -m
Print a warning when encountering a multiple inclusion.
- -sstring
Use string as delimiter in file, instead of # DO NOT
DELETE THIS LINE -- make depend depends on it.
- -v
Verbose. List all files included by main source file.
- -Dname
Define name with the given value (first form) or with value 1
(second form).
- -Idir
Add directory dir to the list of directories searched.
- -Ydir
Search only dir for include files. Ignore standard include
directories.
- mkdirhier dir...
Create directory dir and all missing parent directories
during file installation operations.
- xmkmf [option] [topdir] [curdir]
Bootstrap a Makefile from an Imakefile.
topdir specifies the location of the project root directory.
curdir (usually omitted) is
specified as a relative pathname from the top of the build tree to the
current directory. The -a option is equivalent to the following
command sequence:
% xmkmf
% make Makefiles
% make includes
% make depend
Configuration files
Following is a list of the imake configuration files:
- Imake.tmpl
Master template for imake. Imake.tmpl includes
all the other configuration files, plus the Imakefile in the current
directory.
- Imake.params
Contains definitions that apply across sites and vendors.
- Imake.rules
Contains cpp macro definitions that are configured
for the current platform. The macro definitions are fed into
imake, which runs cpp to process the macros. Newlines (line continuations) are
indicated by the string @@\ (double at sign, backslash).
- site.def
Contains site-specific (as opposed to vendor-specific) information,
such as installation directories, what set of programs to build, and
any special versions of programs to use during the build. The site.def
file changes from machine to machine.
- Project.tmpl
File containing X-specific variables.
- Library.tmpl
File containing library rules.
- Server.tmpl
File containing server-specific rules.
- .cf
The .cf files are the vendor-specific VendorFiles that live in
Imake.vb. A .cf file contains platform-specific definitions,
such as version numbers of the operating system and the compiler and
workarounds for missing commands. The definitions in .cf files
override the defaults, defined in Imake.params.
The Imakefile
The Imakefile is a per-directory file that indicates targets to
be built and installed and rules to be applied. imake
reads the Imakefile and expands the rules into Makefile
target entries. An Imakefile may also include definitions of
make variables and list the dependencies of the targets. The
dependencies are expressed as cpp macros, defined in
Imake.rules. Whenever you change an Imakefile, you need to
rebuild the Makefile and regenerate header file dependencies.
For more information on imake, see
Software Portability with imake by Paul DuBois.
|
imapd | imapd TCP/IP command. The Interactive Mail Access Protocol (IMAP) server daemon.
imapd is invoked by inetd and listens on port
143 for requests from IMAP clients. IMAP allows mail programs
to access remote mailboxes as if they were local. IMAP is a richer protocol
than POP because it allows a client to retrieve message-level
information from a server mailbox instead of the entire
mailbox. IMAP can be used for online and offline reading.
The popular Pine mail client contains support for IMAP.
|
inetd | inetd [option] [configuration_file] TCP/IP command. Internet services daemon. inetd listens on multiple ports for incoming
connection requests. When it receives one, it spawns the appropriate
server. When started, inetd reads its
configuration information from either
configuration_file, or from the default
configuration file /etc/inetd.conf. It then
issues a call to getservbyname,
creates a socket for each server, and binds each socket to the port
for that server. It does a listen on
all connection-based sockets,
then waits, using select for a connection or datagram.
When a connection request is received on a listening socket, inetd does an accept, creating a new socket. It then forks,
dups, and execs the appropriate server. The invoked server has I/O to
stdin, stdout, and stderr done to the new socket, connecting the
server to the client process.
When there is data waiting on a datagram socket, inetd forks, dups, and execs the appropriate
server, passing it any server program arguments. A datagram server
has I/O to stdin, stdout, and stderr done to the original socket. If the
datagram socket is marked as wait,
the invoked server must process the message before inetd considers the socket available for new
connections. If the socket is marked nowait, inetd
continues to process incoming messages on that port.
The following servers may be started by inetd: bootpd,
bootpgw, fingerd, ftpd,
imapd, popd, rexecd,
rlogind, rshd, talkd,
telnetd, and tftpd. Do not arrange for inetd to start named, routed,
rwhod, sendmail, listen, or any NFS server.
inetd rereads its configuration file
when it receives a hangup signal, SIGHUP. Services may be added,
deleted, or modified when the configuration file is reread.
Option
- -d
Turn on socket-level debugging and print debugging information
to stdout.
Files
- /etc/inetd.conf
Default configuration file.
- /var/run/inetd.pid
inetd's process ID.
|
info | info [options] [topics] GNU hypertext reader: display online documentation previously built
from Texinfo input. Info files are arranged in a hierarchy and can
contain menus for subtopics. When entered without options, the
command displays the top-level info file (usually
/usr/local/info/dir). When topics
are specified, find a
subtopic by choosing the first topic from the menu in the
top-level info file, the next topic from the new menu
specified by the first topic, and so on. The initial
display can also be controlled by the
-f and
-n options.
Options
- -d directories, --directory directories
Search directories, a colon-separated list, for
info files. If
this option is not specified, use the INFOPATH environment variable or
the default directory (usually /usr/local/info).
- --dribble file
Store each keystroke in file, which can be used in a
future session with the
--restore
option to return to this place in info.
- -f file, --file file
Display specified info file.
- -n node, --node node
Display specified node in the info file.
- -o file, --output file
Copy output to file instead of displaying it at the
screen.
- --help
Display brief help.
- --restore file
When starting, execute keystrokes in file.
- --subnodes
Display subtopics.
- --version
Display version.
- --vi-keys
Use vi-like key bindings.
|
init | init [option] [runlevel] System administration command.
Option
- -t seconds
When changing runlevels,
send SIGKILL seconds after SIGTERM. Default is 20.
Files
init is the first process run by any Unix machine
at boot time. It verifies the integrity of all filesystems and
then creates other processes, using fork and exec, as specified
by /etc/inittab. Which processes may be run are controlled
by runlevel. All process terminations are recorded in
/var/run/utmp and /var/log/wtmp. When the runlevel
changes, init sends SIGTERM and then, after 20
seconds, SIGKILL to all processes that cannot be run
in the new runlevel.
Runlevels
The current runlevel may be changed by telinit, which is often
just a link to init. The default runlevels vary from
distribution to distribution, but these are standard:
- 0
Halt the system.
- 1, s, S
Single-user mode.
- 6
Reboot the system.
- q, Q
Reread /etc/inittab.
Check the /etc/inittab file for runlevels on your system.
|
insmod | insmod [options] file [symbol=value ...] System administration command.
Load the module file into the kernel, changing any symbols
that are defined on the command line. If the module file is named
file.o or file.mod, the module will be named file.
Options
- -f
Force loading of module, even if some problems are encountered.
- -m
Output a load map.
- -o name
Name module name instead of attempting to name it from the
object file's name.
- -x
Do not export: do not add any external symbols from the module
to the kernel's symbol table.
|
install | install [options] [file] directories System administration command.
Used primarily in makefiles to update files. install copies files
into user-specified directories. It will not overwrite a file. Similar to cp but attempts to set permission modes, owner, and group.
Options
- -d, --directory
Create any missing directories.
- -g group, --group group
Set group ID of new file to group
(privileged users only).
- -m mode, --mode mode
Set permissions of new file to mode (octal or symbolic). By default, the mode
is 0755.
- -o [owner], --owner [owner]
Set ownership to owner or, if unspecified, to root
(privileged users only).
- -s, --strip
Strip symbol tables.
|
ipchains |
ipchains command [options] System administration command. Edit IP firewall rules in the 2.2
Linux kernel. A 2.2 Linux kernel compiled with firewall support will
examine the headers of all network packets and compare them to
matching rules to see what it should do with the packet. A firewall
rule consists of some matching criteria and a target, a result to be
applied if the packet matches the criteria. The rules are organized
into chains. You can use these rules to build a firewall or just
reject certain kinds of network connections.
Firewall rules are organized into chains, an ordered checklist that
the kernel works through looking for matches. There are three built-in
chains input, output, and forward. Packets entering the system are
tested against the input chain.
Those exiting the system are checked against the output chain. If an incoming packet is
destined for some other system, it is checked against the forward chain. Each of these chains has a
default target, a policy, in case no match is found. User-defined
chains can be created and used as targets for packets, but they have
no default policies. If no match can be found in a user-defined
chain, the packet is returned to the chain from which it was called
and tested against the next rule in that chain.
ipchains only changes the rules in
the running kernel. When the system is powered off, all those changes
are lost. You can use the ipchains-save command to make a script you can
later run with ipchains-restore to
restore your firewall settings. Such a script is often called at boot
up and many distributions have an ipchains initialization script that uses the
output from ipchains-save.
Commands
ipchains is always invoked with one
of the following commands:
- -A chain rules,
--append chain rules
Append new rules to chain.
- -I chain number rules,
--insert <chain number rules
Insert rules into chain at the ordinal position given
by number.
- -D chain rules,
--delete chain rules
Delete rules from chain.
Rules can be specified by their ordinal number in the chain as well as by
a general rule description.
- -R chain number rule,
--replace chain number rule
Replace a rule in chain. The rule to be
replaced is specified by its ordinal number.
- -C chain rule,
--check chain rules
Construct a network packet that matches the given rule and
check how chain will handle it. The rule must describe the source,
destination, protocol, and interface of the packet to be constructed.
- -L [chain],
--list $PARAMETER
List the rules in chain. If no chain is specified, list the
rules in all chains.
- -ML,
--masquerading --list
List masquerading connections.
- -MS tcp tcpfin udp,
--masquerading --set tcp tcpfin udp
Set timeout value in seconds for masquerading connections. -MS always takes three parameters specifying the timeout
values for TCP sessions, TCP sessions that have received a FIN packet, and
UDP packets.
- -F chain,
--flush chain
Remove all rules from chain.
- -Z [chain],
--zero [chain]
Reset the packet and byte counters in chain. If no chain is
specified, all chains will be reset. When used without specifying a chain
and combined with the -L command, it lists the current
counter values before they are reset.
- -N chain,
--new-chain chain
Create a new chain. The chain's name must be unique.
- -X [chain],
--delete-chain chain
Delete chain. Only user-defined chains can be deleted, and
there can be no references to the chain to be deleted. If no argument is
given, all user-defined chains will be deleted.
- -P chain target,
--policy chain
target
Set the policy for a built-in chain; the target itself cannot
be a chain.
- -h [icmp]
Print a brief help message. If the option icmp is given,
print a list of valid ICMP types.
Targets
A target can be the name of a chain or one of the following special
values:
- ACCEPT
Let the packet through.
- DENY
Drop the packet.
- MASQ
Masquerade the packet so it appears that it originated from the
current system. Reverse packets from masqueraded connections are
unmasqueraded automatically. This is a legal target for only the
forward chain, or user-defined chains used in forwarding packets.
To use this target, the kernel must be compiled with support for IP
masquerading.
- REDIRECT [port]
Redirect incoming packets to a local port on which you are
running a transparent proxy program. If the specified port is 0 or is not
given, the destination port of the packet is used as the redirection port. REDIRECT is only a legal target for the input chain or user-defined chains used in handling incoming packets. The kernel must be
compiled with support for transparent proxies.
- REJECT
Drop the packet and send an ICMP message back to the sender
indicating the packet was dropped.
- RETURN
Return to the chain from which this chain was called and check the
next rule. If RETURN is the target of a rule in a built-in chain,
then the built-in chain's default policy is applied.
Rule specification parameters
These options are used to create rules for use with the preceding commands. Rules consist of some matching criteria and usually a target to jump
to (-j) if the match is made. Many of the parameters for these
matching rules can be expressed as a negative with an exclamation point (!)
meaning "not." Those rules will match everything except the given parameter.
- -p [!] name,
--protocol [!]$PARAMETER
Match packets of protocol name. The value of
name can be given as a name or number as found in the
file /etc/protocols. The most common values are
tcp, udp, icmp, or the
special value all. The number 0 is
equivalent to all, and this is the default value when this option is
not used.
- -s [!] address[/mask] [!] [port],
--source [!] address[/mask] [!] [port]
Specifies the source address and port of the packet
that will match this rule. The address may be supplied as a hostname, a
network name, or an IP address. The optional mask is the netmask to use
and may be supplied either in the traditional form (e.g., /255.255.255.0)
or in the modern form (e.g., /24). The optional port specifies the TCP,
UDP, or ICMP type that will match. You may supply a port specification
only if you've supplied the -p parameter with one of the
tcp, udp or icmp protocols. A colon can be used to
indicate an inclusive range of ports or ICMP values to be used. (e.g.,
20:25 for ports 20 through 25). If the first port parameter is
missing, the default value is 0. If the second is omitted, the default
value is 65535.
- -d [!] address[/mask] [!] [port],
--destination [!] address[/mask] [port]
Match packets with the destination address.
The syntax for this command's parameters is the same as for the
-s option.
- -j target,
--jump target
Jump to a special target or a user-defined chain. If this option is
not specified for a rule, matching the rule only
increases the rule's
counters and the packet is tested against the next rule.
- -i [!] name,
--interface name
Match packets from interface name[+]. name is the network
interface used by your system (e.g., eth0 or ppp0). A +
can be used as a wildcard, so ppp+ would match any interface name
beginning with ppp.
- [!] -f,
[!]--fragment $PARAMETER
The rule applies to everything but the first fragment of a fragmented packet.
- --source-port [!] port
Match packets from the source port. The syntax
for specifying ports can be found in the preceding description of the
-s option.
- --destination-port [!] port
Match packets with the destination port. The
syntax for specifying ports can be found in the preceding description of the
-s option.
- --icmp-type [!] type
Match packets with ICMP type name or number of type.
Options
- -b,
--bidirectional
Put rule in both the input and output chain so packets will be matched in both directions.
- -v,
--verbose
Verbose mode.
- -n,
--numeric
Print all IP address and port numbers in numeric form. By default,
names are displayed when possible.
- -l,
--log
Log information for the matching packet to the system log.
- -t andmask xormask,
--TOS andmask xormask
Change the Type of Service field in the packet's header. The TOS
field is first ANDed with the 8-bit hexadecimal mask andmask,
then XORed with the 8-bit hexadecimal mask xormask. Rules that
would affect the least significant bit (LSB) portion of the TOS field are rejected.
- -x,
--exact
Expand all numbers in a listing (-L). Display the
exact value of the packet and byte counters instead of rounded
figures.
- [!] -y,
--syn
Match only incoming TCP connection requests, those with the SYN bit
set and the ACK and FIN bits cleared. This blocks incoming TCP
connections but leaves outgoing connections unaffected.
- --line-numbers
Used with the -L command. Add the line number to the
beginning of each rule in a listing indicating its position in the
chain.
- --no-warnings
Disable all warnings
|
ipchains-restore |
ipchains-restore [options] System administration command. Restore firewall rules. ipchains-restore takes commands generated by
ipchains-save and uses them to
restore the firewall rules for each chain. Often used by
initialization scripts to restore firewall settings on boot.
Options
- -f
Force updates of existing chains without asking.
- -v
Print rules as they are being restored.
- -p
If a nonexisting chain is targeted by a rule, create it.
|
ipchains-save |
ipchains-save [chain] [option] System administration command. Print the IP firewall rules currently
stored in the kernel to stdout. If
no chain is given, all chains will be printed.
Output is usually redirected to a file, which can later be used by
ipchains-restore to restore the
firewall.
Option
- -
v
Print out rules to stderr as well as stdout,
making them easier to see when redirecting
output.
|
ipfwadm | ipfwadm
category command
parameters
[options] ipfwadm
-M [ -l |
-s ]
[options]
Administer a
firewall and its rules,
firewall accounting, and IP
masquerading in the 2.0 Linux kernel. This command is replaced with
ipchains in the 2.2 kernel, and
ipchains is replaced by iptables
in the 2.4 kernel.
There are four categories of rules: IP
packet accounting,
IP input
firewall, IP output firewall, and IP forwarding firewall. The rules
are maintained in lists, with a separate list for each category. See
the manpage for ipfw(4) for a more
detailed description of how the lists work.
Each ipfwadm
command specifies only
one category and one rule. To create a secure firewall, you issue
multiple ipfwadm commands; the
combination of their rules work together to ensure that your firewall
operates as you intend it to. The second form of the command is for
masquerading. The commands -l
and -s described in the later
list are the only ones that can be used with the masquerading
category, -M.
Categories
One of the following flags is required to indicate the category of
rules to which the command that follows the category applies.
- -A [direction]
IP accounting rules. Optionally, a direction can
be specified:
- in
Count only incoming packets.
- out
Count only outgoing packets.
- both
Count both incoming and outgoing packets; this is the default.
- -F
IP forwarding firewall rules.
- -I
IP input firewall rules.
- -M
IP masquerading administration. Can
be used only with the -l or -s command.
- -O
IP output firewall rules.
Commands
The category is followed by a command indicating the specific action
to be taken. Unless otherwise specified, only one action can be
given on a command line. For the commands that can include a policy,
the valid policies are:
- accept
Allow matching packets to be received, sent, or forwarded.
- deny
Block matching packets from being received, sent, or forwarded.
- reject
Block matching packets from being received, sent, or forwarded and also
return an ICMP error message to the sending host.
The commands are:
- -a [policy]
Append one or more rules to the end of the rules for the category. No
policy is specified for accounting rules. For firewall rules, a
policy is required. When the source and/or destination names resolve
to more than one address, a rule is added for each possible address
combination.
- -c
Check whether this IP packet would be accepted,
denied, or rejected by the type of firewall represented by this
category. Valid only when the category is
-I, -O, or -F. Requires the -V parameter
to be specified (see "Parameters," later).
- -d [policy]
Delete one or more entries from the list of rules for the
category. No policy is specified for accounting rules.
The parameters specified with this command must
exactly match the parameters from an append or insert command, or no match will
be found and the rule will not be removed. Only the first matching rule in
the list of rules is deleted.
- -f
Remove (flush) all rules for the category.
- -h
Display a help message with a brief description of the command syntax.
Specified with no category:
% ipfwadm -h
- -i [policy]
Insert a new rule at the beginning of the selected list for the
category. No policy is specified for accounting rules. For firewall
rules, a policy is required. When the source and/or destination names
resolve to more than one address, a rule is added for each possible
address combination.
- -l
List all rules for the category. This option may be combined with the
-z option to reset the packet
and byte counters after listing their current values. Unless the
-x option is also specified,
the packet and byte counters are shown as
numberK or
numberM, rounded to the nearest
integer. See also the -e option
described under "Options" later.
- -p policy
Change the default policy for the selected type of
firewall to policy. The default policy is
used when no matching rule is found. Valid only
with -I, -O, or -F.
- -s tcp tcpfin udp
Set the masquerading timeout values; valid only with -M. The three parameters are required and represent the timeout
value in seconds for TCP sessions, TCP sessions after
receiving a FIN packet, and UDP packets, respectively. A timeout value of 0
preserves the current timeout value of the corresponding entry.
- -z
Reset the packet and byte counters for all rules in the category.
This command may be combined with the -l command.
Parameters
The following parameters can be specified with
the -a, -i, -d, or -c commands, except as
noted. Multiple parameters can be specified on a single ipfwadm
command line.
- -D address[/mask] [port ...]
The destination specification (optional). See the
description of -S for the syntax, default values, and
other requirements. ICMP types cannot be specified with -D.
- -P protocol
The protocol of the rule or packet; possible values are
tcp, udp, icmp, or all. Defaults to
all, which matches all protocols. -P cannot be specified with
the -c command.
- -S address[/mask] [port ...]
The source IP address, specified as a hostname, a network name,
or an IP address. The source address and mask default to 0.0.0.0/0.
If -S is specified, -P must also be specified.
The optional mask is specified as a network mask or as the
number of 1s on the left of the network mask (e.g.,
a mask of 24 is equivalent to 255.255.255.0). The mask defaults to 32.
One or more values of port may optionally be specified, indicating
what ports or ICMP types the rule applies to. The default is all. Ports may be specified by their /etc/
services entry. The syntax for indicating a range of ports is:
lowport:highport
For example:
-S 172.29.16.1/24 ftp:ftp-data
- -V address
The address of the network interface the packet is
received from (if category is -I) or is being sent to
(if category is -O). address
can be a hostname or an IP address, and defaults to 0.0.0.0,
which matches any interface address. -V is required with the -c
command:
-V 172.29.16.1
- -W name
Identical to -V but takes a device name instead of
its address:
-W ppp0
Options
- -b
Bidirectional mode. The rule matches IP
packets in both directions. This option is valid
only with the -a, -i, and -d commands.
- -e
Extended output. Used with the -l command to
also show the interface address and any rule
options. When listing firewall rules, also shows the
packet and byte counters and the TOS (Type of Service)
masks.
When used with -M, also shows information related to delta
sequence numbers.
- -k
Match TCP acknowledgment packets (i.e., only TCP packets with the ACK bit
set). This option is ignored for all other protocols and is valid only
with the -a, -i, and -d commands.
- -m
Accept masquerade packets for forwarding, making them appear to have
originated from the local host. Recognizes reverse packets and
automatically demasquerades them, bypassing the forwarding firewall.
This option is valid only in forwarding firewall
rules with policy accept. The
kernel must have been compiled with CONFIG_IP_MASQUERADE defined.
- -n
Numeric output. Print IP addresses and port numbers
in numeric format.
- -o
Log packets that match this rule to the kernel log. This option is valid only
with the -a, -i, and -d commands. The
kernel must have been compiled with CONFIG_IP_FIREWALL_VERBOSE defined.
- -r [port]
Redirect packets to a local socket, even if they were
sent to a remote host. If port is 0 (the default), the packet's
destination port is used. This option is valid only
in input firewall rules with policy accept. The kernel must have
been compiled with CONFIG_IP_TRANSPARENT_ PROXY defined.
- -t andmask xormask
Specify masks used for modifying the TOS field in the IP
header. When a packet is accepted (with or without
masquerading) by a firewall rule, its TOS field is
bitwise ANDed with andmask, and the result
is bitwise XORed with xormask. The masks are specified as 8-bit
hexadecimal values. This option is valid only
with the -a, -i, and -d commands
and has no effect when used with accounting
rules or with firewall rules for rejecting or denying a packet.
- -v
Verbose output. Print detailed information about the
rule or packet to be added, deleted, or checked.
This option is valid only
with the -a, -i, -d, and -c commands.
- -x
Expand numbers. Display the exact value of the
packet and byte counters, instead of a rounded value.
This option is valid only when the counters are being listed
anyway (see also the -e option).
- -y
Match TCP packets with the SYN bit set and the
ACK bit cleared. This option is ignored for
packets of other protocols and is
valid only with the -a, -i, and -d commands.
|
iptables |
iptables command
[options] System administration command. Configure
netfilter filtering rules. In the 2.4 kernel,
the ipchains firewall capabilities
are replaced with the netfilter kernel module.
netfilter can be configured to work just like
ipchains, but it also comes with the
module iptables, which is similar to
ipchains but
extensible. iptables rules consist of some
matching criteria and a target, a result to be applied if the packet
matches the criteria. The rules are organized into chains. You can
use these rules to build a firewall, masquerade your local area
network, or just reject certain kinds of network connections.
There are three built-in tables for iptables, one for network filtering (filter), one for Network Address Translation
(nat), and the last for specialized
packet alterations (mangle).
Firewall rules are organized into chains, ordered check lists of rules
that the kernel works through looking for matches. The filter table has three built-in chains:
INPUT, OUTPUT, and FORWARD. The INPUT and OUTPUT chains handle packets originating from
or destined for the host system. The FORWARD chain handles mail just passing through
the host system. The nat table also
has three built-in chains: PREROUTING, POSTROUTING, and OUTPUT. mangle has only two chains: PREROUTING and OUTPUT.
netfilter checks packets entering the system. After applying any PREROUTING rules
it passes them to the INPUT chain or
to the FORWARD chain if the packet is
just passing through. Upon leaving, the system packets are passed to
the OUTPUT chain and then on to any
POSTROUTING rules. Each of these
chains has a default target, a policy, in case no match is
found. User-defined chains can also be created and used as targets for
packets but do not have default policies. If no match can be found in
a user-defined chain, the packet is returned to the chain from which
it was called and tested against the next rule in that chain.
iptables only changes the rules in
the running kernel. When the system is powered off, all changes are
lost. You can use the iptables-save
command to make a script you can run with iptables-restore to restore your firewall
settings. Such a script is often called at bootup. Many
distributions will have an iptables
initialization script that uses the output from
iptables-save.
Commands
iptables is always invoked with one of the following commands:
- -A chain rules,
--append chain rules
Append new rules to chain.
- -I chain number rules,
--insert chain number rules
Insert rules into chain at the ordinal position given
by number.
- -D chain rules,
--delete chain
rules
Delete rules from chain.
Rules can be specified by their ordinal number in the chain as well as
by a general rule description.
- -R chain number rule,
--replace chain number rule
Replace a rule in chain. The rule to be
replaced is specified by its ordinal number.
- -C chain rule,
--check chain rules
Check how chain will handle a network packet
that matches the given rule. The rule must describe
the source, destination, protocol, and interface of the packet to be
constructed.
- -L [chain],
--list $PARAMETER
List the rules in chain or all chains if chain is not specified.
- -F [chain],
--flush chain
Remove all rules from chain or from all chains
if chain is not specified.
- -Z [chain],
--zero chain
Zero the packet and byte counters in chain. If no chain is
specified, all chains will be reset. When used without specifying a chain
and combined with the -L command,
it lists the current counter values before they are
reset chain.
- -N chain,
--new-chain chain
Create a new chain. The chain's name must be unique. This is how user-defined chains are created.
- -X [chain],
--delete-chain chain
Delete the specified user-defined chain or all
user-defined chains if no chain is specified.
- -P chain target,
--policy chain
target
Set the default policy for a built-in chain; the target itself cannot
be a chain.
- -E old-chain new-chain,
--rename-chain old-chain new-chain
Rename old-chain to new-chain.
- -h [icmp]
Print a brief help message. If the option icmp is given, print a list of valid ICMP types.
Targets
A target may be the name of
a chain or one of the following special values.
- ACCEPT
Let the packet through.
- DROP
Drop the packet.
- QUEUE
Send packets to the user space for processing.
- RETURN
Stop traversing the current chain and return to the point in the
previous chain from which this one was called. If RETURN is the target of a rule in a built-in chain,
the built-in chain's default policy is applied.
Rule specification parameters
These options are used to create rules for use with the preceding commands.
Rules consist of some matching criteria and usually a target to jump
to (-j) if the match is made. Many of
the parameters for these matching rules can be expressed as a negative with
an exclamation point (!) meaning "not." Those rules will match everything
except the given parameter.
- -p [!] name,
--protocol [!]$PARAMETER
Match packets of protocol name. The value of
name can be given as a name or number as found in the
file /etc/protocols. The most common values are
tcp, udp, icmp, or the
special value all. The number 0 is
equivalent to all and this is the default value when this option is not
used. If there are extended matching rules associated with the specified
protocol, they will be loaded automatically. You need not use the
-m option to load them.
- -s [!] address[/mask] [!] [port],
--source [!] address[/mask] [!] [port]
Match packets with the source address.
The address may be supplied as a hostname, a network name, or an IP
address. The optional mask is the netmask to use and may be supplied
either in the traditional form (e.g., /255.255.255.0) or in the modern
form (e.g., /24).
- -d [!] address[/mask] [!] [port],
--destination [!] address[/mask] [port]
Match packets from the destination address. See the
description of -s for the syntax of this option.
- -j target,
--jump target
Jump to a special target or a user-defined chain. If this option is
not specified for a rule, matching the rule only increases the rule's
counters, and the packet is tested against the next rule.
- -i [!] name[+],
--in-interface name[+]
Match packets being received from interface
name. name is the network interface used by your
system (e.g., eth0 or ppp0). A + can be
used as a wildcard, so ppp+ would match any interface name beginning
with ppp
- -o [!] name[+],
--out-interface name[+]
Match packets being sent from interface name.
See the description of -i for the syntax for name.
- [!] -f,
[!]--fragment $PARAMETER
The rule applies only to the second or further fragments of a fragmented packet.
Options
- -v,
--verbose
Verbose mode.
- -n,
--numeric
Print all IP address and port numbers in numeric form. By default,
text names are displayed when possible.
- -x,
--exact
Expand all numbers in a listing (-L). Display the exact value of the packet
and byte counters instead of rounded figures.
- -m module,
--match
Explicitly load matching rule extensions associated with
module. See the following section, "Match Extensions."
- -h [icmp],
--help [icmp]
Print help message. If icmp is specified, a list of valid
ICMP type names will be printed. -h can also be used with
the -m option to get help on an extension module.
- --line-numbers
Used with the -L command. Add the line number to the
beginning of each rule in a listing, indicating its position in the
chain.
Match extensions
Several kernel modules come with netfilter to extend matching
capabilities of rules. Those associated with particular protocols are loaded
automatically when the -p option is used to specify the protocol.
Others need to be loaded explicitly with the -m option.
- tcp
Loaded when -p tcp is the only protocol specified.
- --source-port [!] [port][:port], --sport [!] [port][:port]
Match the specified source ports. Using the colon specifies an
inclusive range of services to match. If the first port is omitted, 0
is the default. If the second port is omitted, 65535 is the default.
You can also use a dash instead of a colon to specify the range.
- --destination-port [!] [port][:port],
--dport [!] [port][:port]
Match the specified destination ports. The syntax is the same as
for --source-port.
- --tcp-flags [!] mask comp
Match the packets with the TCP flags specified by mask and
comp. mask is a comma-separated list of flags that
should be examined. comp is a comma-separated list of flags
that must be set for the rule to match. Valid flags are SYN, ACK,
FIN, RST, URG, PSH, ALL, and NONE.
- [!] --syn
Match packets with the SYN bit set and the ACK and FIN bits
cleared. These are packets that request TCP connections; blocking them
prevents incoming connections. Shorthand for
--tcp-flags SYN,RST,ACK SYN.
- udp
Loaded when -p udp is the only protocol specified.
- --source-port [!] [port][:port],
--sport [!] [port][:port]
Match the specified source ports. The syntax is the same as for the
--source-port option of the TCP
extension.
- --destination-port [!] [port][:port],
--dport [!] [port][:port]
Match the specified destination ports. The syntax is the same as
for --source-port option of the TCP
extension.
- icmp
Loaded when -p icmp is the only protocol specified.
- --icmp-type [!] type
Match the specified icmp type. type may be a
numeric ICMP type or one of the ICMP type names shown by the command
iptables -p icmp -h.
- mac
Loaded explicitly with the -m option.
- --mac-source [!] address
Match the source address that
transmitted the packet. address must be
given in colon-separated hexbyte notation (for example, --mac-source
00:60:08:91:CC:B7.
- limit
Loaded explicitly with the -m option. The limit
extensions are used to limit the number of packets matched. This is
useful when combined with the LOG target. Rules using this
extension match until the specified limit is reached.
- --limit rate
Match addresses at the given rate. rate is
specified as a number with an optional /second, /minute, hour, or
/day suffix. When this option is not set, the default is
'3/hour'.
- --limit-burst [number]
Set the maximum number of packets to match in a burst. Once the number has been reached, no more packets are matched for this
rule until the number has recharged. It recharges at the rate set by
the --limit option. When not specified, the
default is 5.
- multiport
Loaded explicitly with the -m option. The
multiport extensions match sets of source or destination ports.
These rules can be used only in conjunction with -p tcp and -p
udp. Up to 15 ports can be specified in a comma-separated
list.
- --source-port [ports]
Match the given source ports.
- --destination-port [ports]
Match the given destination ports.
- --port [ports]
Match if the packet has the same source and destination port and
that port is one of the given ports.
- mark
Loaded explicitly with the -m option. This module
works with the MARK extension target:
- --mark value[/mask]
Match the given unsigned mark value. If a mask is specified, it
is logically ANDed with the mark before comparison.
- owner
Loaded explicitly with the -m option. The
owner extensions match a local packet's creator's user, group
process, and session IDs. This makes sense only as a part of the
OUTPUT chain.
- --uid-owner userid
Match packets created by a process owned by userid.
- --gid-owner groupid
Match packets created by a process owned by groupid.
- --pid-owner processid
Match packets created by process ID processid.
- --sid-owner sessionid
Match packets created by a process in the session
sessionid.
- state
Loaded explicitly with the -m option. This module matches
the connection state of a packet.
- --state states
Match the packet if it has one of the states in the comma-separated list states. Valid states are INVALID,
ESTABLISHED, NEW, and RELATED.
- tos
Loaded explicitly with the -m option. This module
matches the Type of Service field in a packet's header.
- --tos value
Match the packet if it has a TOS of value. value
can be a numeric value or a Type of Service name. iptables -m tos
-h will give you a list of valid TOS values.
Target extensions
Extension targets are optional additional targets supported by
separate kernel modules. They have their own associated options.
- LOG
Log the packet's information in the system log.
- --log-level level
Set the syslog level by name or number (as defined by
syslog.conf).
- --log-prefix prefix
Begin each log entry with the string prefix. The prefix
string may be up to 30 characters long.
- --log-tcp-sequence
Log the TCP sequence numbers. This is a security risk if your
log is readable by users.
- --log-tcp-options
Log options from the TCP packet header.
- --log-ip-options
Log options from the IP packet header.
- MARK
Used to mark packets with an unsigned integer value you can use
later with the mark matching extension. Valid only with the
mangle table.
- --set-mark value
Mark the packet with value.
- REJECT
Drop the packet and, if appropriate, send an ICMP message back to
the sender indicating the packet was dropped. If the packet was an ICMP
error message, an unknown ICMP type, or a nonhead fragment, or if too many ICMP
messages have already been sent to this address, no message is sent.
- --reject-with type
Send the specified ICMP message type. Valid values are
icmp-net-unreachable, icmp-host-
unreachable,
icmp-port-unreachable, or icmp-proto-unreachable. If
the packet was an ICMP ping packet, type may also be
echo-reply.
- TOS
Set the Type of Service field in the IP header. TOS is a
valid target only for rules in the mangle table.
- --set-tos value
Set the TOS field to value. You can specify this as an
8-bit value or as a TOS name. You can get a list of valid names
using iptables -j TOS -h.
- SNAT
Modify the source address of the packet and all future packets in
the current connection. SNAT is valid only as a part of the
POSTROUTING chain in the nat table.
- --to-source address[-address][port-port]
Specify the new source address or range of addresses. If a
tcp or udp protocol has been specified with the
-p option, source ports may also be specified. If
none is specified, map the new source to the same port if
possible. If not, map ports below 512 to other ports below 512,
those between 512 and 1024 to other ports below 1024, and ports above
1024 to other ports above 1024.
- DNAT
Modify the destination address of the packet and all future packets
in the current connection. DNAT is valid only as a part of the
POSTROUTING chain in the nat table.
- --to-destination address[-address][port-port]
Specify the new destination address or range of addresses. The
arguments for this option are the same as the
--to-source argument for the SNAT
extension target.
- MASQUERADE
Masquerade the packet so it appears that it originated from the
current system. Reverse packets from masqueraded connections are
unmasqueraded automatically. This is a legal target only for chains in
the nat table that handle incoming packets and should be used only
with dynamic IP addresses (like dial-up.) For static addresses use
DNAT.
- --to-ports port[-port]
Specify the port or range of ports to use when masquerading.
This option is only valid if a tcp or udp protocol has
been specified with the -p option. If this option is
not used, the masqueraded packet's port will not be changed.
- REDIRECT [--to-port port]
Redirect the packet to a local port. This is useful for
creating transparent proxies.
- --to-ports port[-port]
Specify the port or range of ports on the local system to which
the packet should be redirected. This option is valid only if a
tcp or udp protocol has been specified with the
-p option. If this option is not used, the redirected
packet's port will not be changed.
|
iptables-restore |
iptables-restore [file] System administration command. Restore firewall rules.
iptables-restore takes commands generated by
iptables-save and uses them to
restore the firewall rules for each chain. Often used by
initialization scripts to restore firewall settings on boot.
file is the name of a file whose contents were
generated by iptables-save. If not
specified, the command takes its input from stdin. This command was
not completed at the time this book went to print. There may be
options not listed here.
|
iptables-save |
iptables-save [chain] System administration command. Print the IP firewall rules currently
stored in the kernel to stdout. If no chain is
given, all chains will be printed. Output may be redirected to a file
that can later be used by iptables-restore to restore the firewall. This
command was not completed at the time this book went to print. There
may be options not listed here.
|
ispell | ispell [options] [files] Compare the words of one or more named files with the system
dictionary. Display unrecognized words on the top of the screen,
accompanied by possible correct spellings, and allow editing,
via a series of commands.
Options
- -b
Back up original file in filename.bak.
- -d file
Search file instead of standard dictionary file.
- -m
Suggest different root/affix combinations.
- -n
Expect nroff or troff input file.
- -p file
Search file instead of personal dictionary file.
- -t
Expect TeX or LaTeX input file.
- -w chars
Consider chars to be legal, in addition to a-z and A-Z.
- -x
Do not back up original file.
- -B
Search for missing blanks (resulting in concatenated words) in addition
to ordinary misspellings.
- -C
Do not produce error messages in response to concatenated words.
- -L number
Show number lines of context.
- -M
List interactive commands at bottom of screen.
- -N
Suppress printing of interactive commands.
- -P
Do not attempt to suggest more root/affix combinations.
- -S
Sort suggested replacements by likelihood that each is correct.
- -T type
Expect all files to be formatted by type.
- -W n
Never consider words that are n characters or less to be misspelled.
- -V
Use hat notation (^L) to display control characters and M-
to display
characters with the high bit set.
Interactive Commands
- ?
Display help screen.
- space character
Accept the word in this instance.
- number
Replace with suggested word that corresponds to
number.
- !command
Invoke shell and execute command in it. Prompt before exiting.
- a
Accept word as correctly spelled, but do not add it to personal
dictionary.
- i
Accept word and add it (capitalized, if so in file) to
personal dictionary.
- l
Search system dictionary for words.
- q
Exit without saving.
- r
Replace word.
- u
Accept word and add lowercase version of it to personal dictionary.
- x
Skip to the next file, saving changes.
- ^L
Redraw screen.
- ^Z
Suspend ispell.
|
join | join [options] file1 file2 Join lines of two sorted files by matching on a common
field. If either file1 or
file2 is -, read from standard input.
Options
- -a filenum
Print a line for each unpairable line in file filenum,
in addition to the normal output.
- -e string
Replace missing input fields with string.
- -i, --ignore-case
Ignore case differences when comparing keys.
- -1 fieldnum1
Join field in file1 is fieldnum1.
Default is the first field.
- -2 fieldnum2
Join field in file2 is fieldnum2.
Default is the first field.
- -o fieldlist
Order the output fields according to fieldlist, where
each entry in the list is in the form
filenum.fieldnum. Entries are
separated by commas or blanks.
- -t char
Specifies the field-separator character (default is
whitespace
).
- -v filenum
Print only unpairable lines from file filenum.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
|
kbd_mode | kbd_mode [option] Print or set the current keyboard mode, which may be RAW, MEDIUMRAW, or
XLATE.
Options
- -a
Set mode to XLATE (ASCII mode).
- -k
Set mode to MEDIUMRAW (keycode mode).
- -s
Set mode to RAW (scancode mode).
- -u
Set mode to UNICODE (UTF-8 mode).
|
kbdrate | kbdrate [options] System administration command.
Control the rate at which the keyboard repeats characters, as well
as its delay time. Using this command without options sets a
repeat rate of 10.9 characters per
second; the default delay is 250 milliseconds. When Linux boots,
however, it sets the keyboard rate to 30 characters per second.
Options
- -s
Suppress printing of messages.
- -r rate
Specify the repeat rate, which must be one of the following
numbers (all in characters per second):
2.0, 2.1, 2.3, 2.5,
2.7, 3.0, 3.3, 3.7, 4.0, 4.3, 4.6, 5.0, 5.5, 6.0,
6.7,
7.5, 8.0, 8.6, 9.2, 10.0, 10.9, 12.0, 13.3,
15.0, 16.0, 17.1, 18.5, 20.0, 21.8, 24.0, 26.7, or 30.0.
- -d delay
Specify the delay, which must be one of the following (in milliseconds):
250, 500, 750, or 1000.
|
kerneld | kerneld System administration command.
kerneld automatically loads kernel modules when they are needed,
thereby reducing kernel memory usage from unused loaded modules
and replacing manual loading of modules with modprobe or insmod.
If a module has not been used for more than one minute, kerneld
automatically removes it.
kerneld comes with the modules-utilities package and is set up
during kernel configuration; its functionality is provided by interactions
between that package and the kernel. kerneld is aware of most common types of
modules. When more than one possible module can be used for a
device (such as a network driver), kerneld uses the
configuration file /etc/conf.modules, which contains path
information and aliases for all loadable modules, to determine the
correct module choice.
kerneld can also be used to implement dial-on-demand
networking, such as SLIP or PPP connections.
The network connection request can be processed by kerneld to
load
the proper modules and set up the connection to the server.
|
kill | kill [option] IDs This is the /bin/kill command; there is also
a shell command of the same name.
Send a signal to terminate one or more process IDs.
You must own the process or be a privileged user.
If no signal is specified, TERM is sent.
Options
- -l
List all signals.
- -p
Print the process ID of the named process, but don't send it a signal. To use this option, specify the full path (e.g.,
/bin/kill -p).
- -signal
The signal number (from /usr/include/sys/signal.h)
or name (from kill -l). With a
signal number of 9 (HUP), the kill cannot be caught by the process; use this
to kill a process that a plain kill doesn't terminate. The
default is TERM.
|
killall | killall [options] names Kill processes by command name. If more than one process is running the
specified command, kill all of them.
Treat command names that contain a / as files;
kill all processes
that are executing that file.
Options
- -signal
Send signal to process (default is TERM).
signal may be a name or number.
- -e
Require an exact match to kill very long names
(i.e., longer than 15 characters).
Normally, killall kills everything that
matches within the first 15 characters.
With -e, such entries are skipped.
(Use -v to print a message
for each skipped entry.)
- -g
Kill the process group to which the process belongs.
- -i
Prompt for confirmation before killing processes.
- -l
List known signal names.
- -q
Quiet; do not complain of processes not killed.
- -v
Verbose: after killing process, report success and process ID.
- -V
Print version information.
- -w
Wait for all killed processes to die. Note that killall may wait forever if the
signal was ignored or had no effect, or if the process stays
in zombie state.
|
killall5 | killall5 The System V equivalent of killall, this command kills all processes except those on which it depends.
|
klogd | klogd [options] System administration command.
Control which kernel messages are displayed on the console; prioritize
all messages, and log them through syslogd. On many operating
systems, syslogd performs all the work of klogd, but
on Linux the features are separated. Kernel messages are gleaned from
the /proc filesystem and from system calls to syslogd. By
default, no messages appear on the console. Messages are sorted into
8 levels, 0-7, and the level number is prepended to each message.
Priority levels
- 0
Emergency situation (KERN_EMERG).
- 1
A crucial error has occurred (KERN_ALERT).
- 2
A serious error has occurred (KERN_CRIT).
- 3
An error has occurred (KERN_ERR).
- 4
A warning message (KERN_WARNING).
- 5
The situation is normal but should be checked (KERN_NOTICE).
- 6
Information only (KERN_INFO).
- 7
Debugging messages (KERN_DEBUG).
Options
- -c level
Print all messages of a higher priority (lower number) than level
to the console.
- -d
Debugging mode.
- -f file
Print all messages to file; suppress normal logging.
- -k file
Use file as source of kernel symbols.
- -n
Avoid autobackgrounding. This is needed when klogd is started
from init.
- -o
One-shot mode. Prioritize and log all current messages, then immediately
exit.
- -s
Suppress reading of messages from the /proc filesystem.
Files
- /usr/include/linux/kernel.h, /usr/include/sys/syslog.h
Sources for definitions of each logging level
- /proc/kmsg
A file examined by klogd for messages
- /var/run/klogd.pid
klogd's process ID
|
ksyms | ksyms [options] System administration command.
Print a list of all exported kernel symbols (name, address, and
defining module, if applicable).
Options
- -a
Include symbols from unloaded modules.
- -h
Suppress header message.
- -m
Include starting address and size. Useful only for symbols in
loaded modules.
File
- /proc/ksyms
Another source of the same information
|
lastlog |
lastlog [options] System administration command. Print the last login times for system
accounts. Login information is read from the file
/var/log/lastlog.
Options
- -tn
Print only logins more recent than n days ago.
- -uname
Print only login information for user name.
|
ld | ld [options] objfiles Combine several objfiles, in the specified order, into
a single executable object module (a.out by default).
ld is the link editor and is often invoked automatically by compiler
commands.
Options
- -c file
Consult file for commands.
- -d, -dc, -dp
Force the assignment of space to common symbols.
- -defsym symbol=expression
Create the global symbol with the value expression.
- -e symbol
Set symbol as the address of the output file's entry point.
- -i
Produce a linkable output file; attempt to set its magic number
to OMAGIC.
- -larch
Include the archive file arch in the list of files to link.
- -m linker
Emulate linker.
- -n
Make text read-only; attempt to set NMAGIC.
- -noinhibit-exec
Produce output file even if errors are encountered.
- -o output
Place output in output, instead of a.out.
- -oformat format
Specify output format.
- -r
Produce a linkable output file; attempt to set its magic number
to OMAGIC.
- -s
Do not include any symbol information in output.
- -shared
Create a shared library.
- -sort-common
Do not sort global common symbols by size.
- -t
Announce each input file's name as it is processed.
- -u symbol
Force symbol to be undefined.
- -v, --version
Show version number.
- --verbose
Print information about ld; print the names of input files
while attempting to open them.
- -warn-common
Warn when encountering common symbols combined with other constructs.
- -warn-once
Provide only one warning per undefined symbol.
- -x
With -s or -S, delete all local symbols that begin with L.
- -L dir
Search directory dir before standard search directories
(this option must precede the -l option that searches that directory).
- -M
Display a link map on standard out.
- -Map file
Print a link map to file.
- -N
Allow reading of and writing to both data and text;
mark ouput if it supports Unix magic numbers;
do not page-align data.
- -R file
Obtain symbol names and addresses from file, but suppress
relocation of file and its inclusion in output.
- -S
Do not include debugger symbol information in output.
- -Tbss address
Begin bss segment of output at address.
- -Tdata address
Begin data segment of output at address.
- -Ttext address
Begin text segment of output at address.
- -Ur
Synonymous with -r except when linking C++ programs, where
it resolves constructor references.
- -X
With -s or -S, delete local symbols beginning with L.
- -V
Show version number and emulation linkers for -m option.
|
ldconfig | ldconfig [options] directories System administration command.
Examine the libraries in the given directories, /etc/ld.so.conf,
/usr/lib, and /lib; update links and cache where necessary.
Usually run in startup files or after the installation of new shared
libraries.
Options
- -D
Debug. Suppress all normal operations.
- -l
Library mode. Expect libraries as arguments, not directories. Manually link specified libraries.
- -n
Suppress examination of /usr/lib and /lib and reading of
/etc/ld.so.conf; do not cache.
- -N
Do not cache; only link.
- -p
Print all directories and candidate libraries in the cache.
Expects no arguments.
- -v
Verbose. Include version number, and announce each directory as
it is scanned and links as they are created.
- -X
Do not link; only rebuild cache.
Files
- /lib/ld.so
Linker and loader.
- /etc/ld.so.conf
List of directories that contain libraries.
- /etc/ld.so.cache
List of the libraries found in those libraries mentioned in
/etc/ld.so.conf.
|
ldd | ldd [options] programs Display a list of the shared libraries each program requires.
Options
- -v
Display ldd's version.
- -V
Display the linker's version.
|
less | less [options] [filename] less is a program for paging through
files or other output. It was written in reaction to the perceived
primitiveness of more (hence its
name). Some commands may be preceded by a number.
Options
- -[z]num
Set number of lines to scroll to num. Default is one
screenful. A negative num sets the number to num
lines less than the current number.
- +[+]command
Run command on startup. If command is a number, jump
to that line. The option ++ applies this command to each file in
the command-line list.
- -?
Print help screen. Ignore all other options; do not page through file.
- -a
When searching, begin after last line displayed. (Default is to search from
second line displayed.)
- -bbuffers
Use buffers buffers for each file (default is 10). Buffers are 1 kilobyte
in size.
- -c
Redraw screen from top, not bottom.
- -d
Suppress dumb-terminal error messages.
- -e
Automatically exit after reaching EOF twice.
- -f
Force opening of directories and devices; do not print warning when
opening binaries.
- -g
Highlight only string found by past search command, not all matching strings.
- -hnum
Never scroll backward more than num lines at once.
- -i
Make searches case-insensitive, unless the search string contains
uppercase letters.
- -jnum
Position target line on line num of screen. Target line can be the result of a search or a jump. Count lines beginning from 1 (top line). A negative num is
counted back from bottom of screen.
- -kfile
Read file to define special key bindings.
- -m
Display more-like prompt, including percent of file read.
- -n
Do not calculate line numbers. Affects -m and -M options and
= and v commands (disables passing of line number to editor).
- -ofile
When input is from a pipe, copy output to file as well as to
screen. (Prompt for overwrite authority if file exists.)
- -ppattern
At startup, search for first occurrence of pattern.
- m
Set medium prompt (specified by -m).
- M
Set long prompt (specified by -M).
- =
Set message printed by = command.
- -q
Disable ringing of bell on attempts to scroll past EOF or before
beginning of file. Attempt to use visual bell instead.
- -r
Display "raw" control characters, instead of using ^x notation.
Sometimes leads to display problems.
- -s
Print successive blank lines as one line.
- -ttag
Edit file containing tag. Consult ./tags (constructed by
ctags).
- -u
Treat backspaces and carriage returns as printable input.
- -w
Print lines after EOF as blanks instead of tildes (~).
- -xn
Set tab stops to every n characters. Default is 8.
- -yn
Never scroll forward more than n lines at once.
- -B
Do not automatically allocate buffers for data read from a pipe.
If -b specifies a number of buffers, allocate that many.
If necessary, allow information from previous screens to be lost.
- -C
Redraw screen by clearing it and then redrawing from top.
- -E
Automatically exit after reaching EOF once.
- -G
Never highlight matching search strings.
- -I
Make searches case-insensitive, even when the search string contains
uppercase letters.
- -M
Prompt more verbosely than with -m, including percentage, line
number, and total lines.
- -N
Print line number before each line.
- -Ofile
Similar to -o but does not prompt when overwriting file.
- -P[m,M,=]prompt
Set prompt (as defined by -m, -M, or =).
Default is short prompt (-m).
- -Q
Never ring terminal bell.
- -S
Cut, do not fold, long lines.
- -Tfile
With the -t option or :t command, read file
instead of ./tags.
- -U
Treat backspaces and carriage returns as control characters.
- -X
Do not send initialization and deinitialization strings from
termcap to terminal.
Commands
Many commands can be preceded by a numeric argument, referred to as
number in the command descriptions.
- SPACE, ^V, f, ^F
Scroll forward the default number of lines (usually one windowful).
- z
Similar to SPACE but allows the number of lines to be specified,
in which case it resets the default to that number.
- RETURN, ^N, e, ^E, j, ^J
Scroll forward. Default is one line. Display all lines, even if
the default is more lines than the screen size.
- d, ^D
Scroll forward. Default is one-half the screen size. The number of
lines may be specified, in which case the default is reset.
- b, ^B, ESC-v
Scroll backward. Default is one windowful.
- w
Like b but allows the number of lines to be specified, in which case
it resets the default to that number.
- y, ^Y, ^P, k, ^K
Scroll backward. Default is one line. Display all lines, even if
the default is more lines than the screen size.
- u, ^U
Scroll backward. Default is one-half the screen size. The number of
lines may be specified, in which case the default is reset.
- r, ^R, ^L
Redraw screen.
- R
Like r but discard buffered input.
- F
Scroll forward. When an EOF is reached, continue trying to find
more output, behaving similarly to tail -f.
- g, <, ESC-<
Skip to a line. Default is 1.
- G, >, ESC->
Skip to a line. Default is the last one.
- p, %
Skip to a position
number percent of the way into the file.
- {
If the top line on the screen includes a {, find its matching }.
If the top line contains multiple {s,
use number to
determine which one to use in finding a match.
- }
If the bottom line on the screen includes a }, find its matching {.
If the bottom line contains multiple }s, use number to
determine which one to use in finding a match.
- (
If the top line on the screen includes a (, find its matching ).
If the top line contains multiple (s,
use number to
determine which one to use in finding a match.
- )
If the bottom line on the screen includes a ), find its matching (.
If the bottom line contains multiple )s,
use number to
determine which one to use in finding a match.
- [
If the top line on the screen includes a [, find its matching ].
If the top line contains multiple [s,
use number to
determine which one to use in finding a match.
- ]
If the bottom line on the screen includes a ], find its matching [.
If the bottom line contains multiple ]s,
use number to
determine which one to use in finding a match.
- ESC-^F
Behave like { but prompt for two characters, which it
substitutes for { and } in its search.
- ESC-^B
Behave like } but prompt for two characters, which it
substitutes for { and } in its search.
- m
Prompt for a lowercase letter and then use that letter to
mark the current position.
- '
Prompt for a lowercase letter and then go to the position
marked by that letter. There are some special characters:
- '
Return to position before last "large movement."
- ^
Beginning of file.
- $
End of file.
- ^X^X
Same as '.
- /pattern
Find next occurrence of pattern, starting at second line displayed. Some special characters can be entered before pattern:
- !
Find lines that do not contain pattern.
- *
If current file does not contain pattern, continue through the
rest of the files in the command line list.
- @
Search from the first line in the first file specified on the command
line, no matter what the screen currently displays.
- ?pattern
Search backward, beginning at the line before the top line.
Treats !, *, and @ as special characters when they begin pattern, as
/ does.
- ESC-/pattern
Same as /*.
- ESC-?pattern
Same as ?*.
- n
Repeat last pattern search.
- N
Repeat last pattern search, in the reverse direction.
- ESC-n
Repeat previous search command but as though it were prefaced by *.
- ESC-N
Repeat previous search command but as though it were prefaced by * and in
the opposite direction.
- ESC-u
Toggle search highlighting.
- :e [filename]
Read in filename and insert it into the command-line list of filenames. Without filename, reread the current file.
filename may contain special characters:
- %
Name of current file
- #
Name of previous file
- ^X^V, E
Same as :e.
- :n
Read in next file in command-line list.
- :p
Read in previous file in command-line list.
- :x
Read in first file in command-line list.
- :f, =, ^G
Print filename, position in command-line list, line number on top
of window, total lines, byte number, and total bytes.
- -
Expects to be followed by a command-line option letter. Toggles the value of that option or, if appropriate, prompts
for its new value.
- -+
Expects to be followed by a command-line option letter. Resets that option to its default.
- --
Expects to be followed by a command-line option letter. Resets that option to the opposite of its default, where the opposite
can be determined.
- _
Expects to be followed by a command-line option letter.
Display that option's current
setting.
- +command
Execute command each time a new file is read in.
- q, :q, :Q, ZZ
Exit.
- v
Not valid for all versions. Invoke editor specified
by $VISUAL or $EDITOR, or vi if neither is set.
- ! [command]
Not valid for all versions.
Invoke $SHELL or sh. If command is given, run it and then exit.
Special characters:
- %
Name of current file
- #
Name of previous file
- !!
Last shell command
- | mark-letter command
Not valid for all versions. Pipe fragment of file (from first line on screen
to mark-letter) to command. mark-letter may also be:
- ^
Beginning of file.
- $
End of file.
- ., newline
Current screen is piped.
Prompts
The prompt interprets certain sequences specially.
Those beginning with % are always
evaluated. Those beginning with ? are
evaluated if certain conditions are true.
Some prompts determine the position of particular lines on the screen.
These sequences require that a method of determining that line
be specified. See the -P option
and the manpage for more information.
|
ln | ln [options] sourcename [destname] ln [options] sourcenames destdirectory
Create pseudonyms (links) for files, allowing them to be
accessed by different names. In the first form, link sourcename to
destname, where destname is usually a new filename, or
(by default) the current directory. If
destname is an existing file, it is overwritten; if destname is
an existing directory, a link named sourcename is created in that
directory. In the second form, create links in destdirectory, each
link having the same name as the file specified.
Options
- -b, --backup
Back up files before removing the originals.
- -d, -F, --directory
Allow hard links to directories. Available to privileged users.
- -f, --force
Force the link (don't prompt for overwrite permission).
- --help
Print a help message and then exit.
- -i, --interactive
Prompt for permission before removing files.
- -n, --no-dereference
Replace symbolic links to directories instead of dereferencing them.
--force is useful with this option.
- -s, --symbolic
Create a symbolic link. This lets you link across filesystems and
also see the name of the link when you run
ls -l (otherwise,
there's no way to know the name that a file is linked to).
- -S suffix, --suffix suffix
Append suffix to files when making backups, instead
of the default ~.
- -v, --verbose
Verbose mode.
- --version
Print version information and then exit.
- -V, --version-control value
Control the types of backups made. The acceptable values for version-control
are:
- t, numbered
Numbered.
- nil,existing
Simple (~) unless a numbered backup exists; then make a numbered backup.
- never, simple
Simple.
|
locate | locate [options] pattern Search database(s) of filenames and print matches. *, ?, [, and ]
are treated specially; / and . are not. Matches include all files
that contain pattern, unless pattern
includes metacharacters, in which case locate
requires an exact match.
Options
- -d path, --database=path
Search databases in path. path
must be a colon-
separated list.
- -h, --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
lockfile | lockfile [options] filenames Create semaphore file(s), used to limit access to a file.
When lockfile fails to create some of the specified files,
it pauses for 8 seconds and retries the last one on which it failed.
The command processes flags as they are encountered (i.e., a flag that is
specified after a file will not affect that file).
Options
- -sleeptime
Time lockfile waits before
retrying after a failed creation attempt. Default is 8 seconds.
- -!
Invert return value. Useful in shell scripts.
- -l lockout_time
Time (in seconds) after a lockfile was last modified at which it will be
removed by force. See also -s.
- -ml, -mu
If the permissions on the system mail spool directory
allow it or if lockfile is suitably setgid,
it can lock and unlock your system mailbox with the
options -ml and
-mu, respectively.
- -r retries
Stop trying to create files after retries retries. The
default is -1 (never stop trying). When giving up, remove all
created files.
- -s suspend_time
After a lockfile has been removed by force (see
-l),
a suspension of 16 seconds takes place by default.
(This is intended to prevent the inadvertent immediate
removal of any lockfile newly created by another program.)
Use -s to change the default 16 seconds.
|
logger | logger [options] [message...] TCP/IP command. Add entries to the system log (via syslogd).
A message can be given on the
command line, or standard input is logged.
Options
- -f file
Read message from file.
- -i
Include the process ID of the logger process.
- -p pri
Enter message with the specified priority pri. Default is user.notice.
- -t tag
Mark every line in the log with the specified tag.
|
login | login [name | option] Log in to the system. login asks for a
username (name
can be supplied on the command line) and password (if appropriate).
If successful, login updates
accounting files, sets various environment variables, notifies
users if they have mail, and executes startup shell files.
Only the root user can log in when /etc/nologin exists.
That file is displayed before the connection is terminated. Furthermore,
root may connect only on a tty that is listed in
/etc/securetty.
If ~/.hushlogin exists, execute a quiet login. If
/var/adm/lastlog exists, print the time of the last login.
Options
- -f
Suppress second login authentication.
- -h host
Specify name of remote host. Normally used by servers, not
humans; may be used only by root.
- -p
Preserve previous environment.
|
logname | logname [option] Consult /var/run/utmp for user's login
name. If found, print it; otherwise, exit with an error message.
Options
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
logrotate | logrotate [options] config_files System administration command.
Manipulate log files according to commands given in
config_files.
Options
- -d
Debug mode. No changes will be made to log files.
- -s, --state file
Save state information in file. The default is
/var/lib/logrotate.status.
- --usage
Usage version and copyright information.
Commands
- compress
Compress old versions of log files with gzip.
- copytruncate
Copy log file, then truncate it in place. For use with
programs whose logging cannot be temporarily halted.
- create [permissions] [owner] [group]
After rotation, re-create log file with the specified
permissions, owner, and group. permissions
must be in octal. If any of these parameters is missing,
the log file's original attributes will be used.
- daily
Rotate log files every day.
- delaycompress
Don't compress log file until the next rotation.
- errors address
Mail any errors to the given address.
- endscript
End a postrotate or prerotate script.
- ifempty
Rotate log file even if it is empty. Overrides the default
notifempty option.
- include file
Read the file into current file. If file is a
directory, read all files in that directory into the current file.
- mail address
Mail any deleted logs to address.
- monthly
Rotate log files only the first time logrotate is
run in a month.
- nocompress
Override compress.
- nocopytruncate
Override copytruncate.
- nocreate
Override create.
- nodelaycompress
Override delaycompress.
- noolddir
Override olddir.
- notifempty
Override ifempty.
- olddir directory
Move logs into directory for rotation. directory
must be on the same physical device as the original log files.
- postrotate
Begin a script of directives to apply after the log file is
rotated. The script ends when the endscript directive
is read.
- prerotate
Begin a script of directives to apply before a log file is
rotated. The script ends when the endscript directive
is read.
- rotate number
The number of times to rotate a log file before removing it.
- size n[k|M]
Rotate log file when it is greater than n bytes. n can
optionally be followed by k for kilobytes or M for megabytes.
|
look | look [options] string [file] Search for lines in file
(/usr/dict/words by default) that begin
with string.
Options
- -a
Use alternate dictionary /usr/dict/web2.
- -d
Compare only alphanumeric characters.
- -f
Search is not case-sensitive.
- -t character
Stop checking after the first occurrence of character.
|
lpc | lpc [command] System administration command.
Control line printer. If executed without a command, lpc
will accept commands from standard input.
Commands
- ?, help [commands]
Get a list of commands or help on specific commands.
- abort all|printer
Terminate current printer daemon and disable printing for the specified
printer.
- clean all|printer
Remove files that cannot be printed from the specified printer
queues.
- disable all|printer
Disable specified printer queues.
- down all|printer message
Disable specified printer queues and put message in
the printer status file.
- enable all|printer
Enable the specified printer queues.
- exit, quit
Exit lpc.
- restart all|printer
Try to restart printer daemons for the specified printers.
- start all|printer
Enable the printer queues and start printing daemons for the specified
printers.
- status all|printer
Return the status of the specified printers.
- stop all|printer
Disable the specified printer daemons after any current jobs are completed.
- topq printer [jobnumbers] [users]
Put the specifed jobs at the top of the printer's queue in the order
the jobs are listed.
- up all|printer
Enable print queues and restart daemons for the specified printers.
|
lpd | lpd [option] [port] TCP/IP command. Line printer daemon.
lpd is usually invoked at boot time from the
rc2 file. It makes a single pass through the printer
configuration file (traditionally /etc/printcap)
to find out about the existing printers and prints any files left after
a crash. It then accepts requests to print files in a queue, transfer
files to a spooling area, display a queue's status, or remove jobs from
a queue. In each case, it forks a child process for each request, then
continues to listen for subsequent requests. If port is
specified, lpd listens on that port; otherwise, it
uses the getservbyname call to ascertain the correct port.
The file lock in each spool directory prevents multiple daemons
from becoming active simultaneously. After the daemon has set the lock,
it scans the directory for files beginning wth cf. Lines in each
cf file specify files to be printed or nonprinting actions to
be performed.
Each line begins with a key character,
which specifies information about the print job or
what to do with the remainder of the line. Key characters are:
- C
Classification -- string to be used for the classification line on the
burst page.
- c
cifplot file.
- f
Formatted file -- name of a file to print that is already formatted.
- g
Graph file.
- H
Hostname -- name of machine where lpd was invoked.
- J
Job name -- string to be used for the jobname on the burst page.
- L
Literal -- this line contains identification information from the password
file and causes the banner page to be printed.
- l
Formatted file, but suppress page breaks and printing of control characters.
- M
Mail -- send mail to the specified user when the current print job completes.
- n
ditroff file.
- P
Person -- login name of person who invoked lpd.
- r
DVI file.
- T
Title -- string to be used as the title for pr.
- t
troff file.
- U
Unlink -- name of file to remove upon completion of printing.
Option
- -l
Enable logging of all valid requests.
Files
- /etc/printcap
Printer description file
- /var/spool/*
Spool directories
- /var/spool/*/minfree
Minimum free space to leave
- /dev/lp*
Printer devices
- /etc/hosts.equiv
Machine names allowed printer access
- /etc/hosts.lpd
Machine names allowed printer access,
but not under same administrative control
|
lpq | lpq [options] [user] Check the print spool queue for status of print jobs.
For each job, display username, rank in the queue,
filenames, job number, and total file size (in bytes). If
user is
specified, display information only for that user.
Options
- -l
Print information about each file comprising a job.
- -Pprinter
Specify which printer to query. Without this option,
lpq
uses the printer set in the PRINTER environment variable or the
default system printer.
- num
Check status for job number num.
|
lpr | lpr [options] files Send files to the printer spool queue.
Options
- -c
Expect data produced by cifplot.
- -d
Expect data produced by TeX in the DVI (device-
independent) format.
- -f
Use a filter that interprets the first character of each line as a
standard carriage control character.
- -g
Expect standard plot data as produced by the
plot routines.
- -l
Use a filter that allows control characters to be printed and suppresses
page breaks.
- -n
Expect data from ditroff
(device-independent troff).
- -p
Use pr to format the files.
- -t
Expect data from troff
(phototypesetter commands).
- -v
Expect a raster image for devices like the Benson
Varian.
- -Pprinter
Output to printer instead of the printer specified
in the PRINTER environment variable or the system default.
- -h
Do not print the burst page.
- -m
Send mail to notify of completion.
- -r
Remove the file upon completion of spooling. Cannot be used
with the -s option.
- -s
Use symbolic links instead of copying files to the spool directory. This can save time and disk space for large files. Files should
not be modified or removed until they have been printed.
- -#num
Print num copies of each listed file.
- -C string
Replace system name on the burst page with string.
- -J name
Replace the job name on the burst page with name. If
omitted, uses the first file's name.
- -T title
Use title as the title
when using pr.
- -i [cols]
Indent the output. Default is 8 columns. Specify number of columns
to indent with the cols argument.
- -w num
Set num characters as the page width for pr.
|
lprm | lprm [options] [jobnum] [user] Remove a print job from the print spool queue. You
must specify a job number or numbers, which can be obtained
from lpq. A privileged user may use the user
parameter to remove all files belonging to a particular user
or users.
Options
- -Pprinter
Specify printer name. Normally, the default printer or printer
specified in the PRINTER environment variable is used.
- -
Remove all jobs in the spool owned by user.
|
lpstat | lpstat [options] Show the status of the print queue. With options that take a
list argument, omitting the list produces all
information for that option. list can be
separated by commas or, if enclosed in double quotes, by spaces.
Options
- -a [list]
Show whether the list of printer or class names is accepting requests.
- -c [list]
Show information about printer classes named in list.
- -d
Show the default printer destination.
- -f [list]
Verify that the list of forms is known to lp.
- -l
Use after -f to describe available forms, after -p to show printer
configurations, or after -s to describe printers appropriate
for the specified character set or print wheel.
- -o [list]
Show the status of output requests. list contains printer names,
class names, or request IDs.
- -p [list]
Show the status of printers named in list.
- -r
Show whether the print scheduler is on or off.
- -R
Show the job's position in the print queue.
- -s
Summarize the print status (shows almost everything).
- -t
Show all status information (reports everything).
- -u [list]
Show request status for users on list. list can
be all to show information on all users.
- -v [list]
Show device associated with each printer named in list.
|
lptest | lptest [length] [count] Generate a lineprinter test pattern on standard output. Prints a standard
ripple pattern of all printable ASCII characters, offset by one position
on each succeeding line.
Parameters
- length
Specify the output line length (default is 79).
- count
Specify the number of lines to print (default is 200).
|
ls | ls [options] [names] List contents of directories. If no names are given, list
the files in the current directory. With one or more names, list
files contained in a directory name or that match a file
name. names can include filename metacharacters. The
options let you display a variety of information in different formats.
The most useful options include -F, -R, -l, and
-s. Some options don't make sense together (e.g., -u and
-c).
Options
- -1, --format=single-column
Print one entry per line of output.
- -a
List all files, including the normally hidden files whose names begin with
a period.
- -b, --escape
Display nonprinting characters in octal and alphabetic format.
- -c, --time-ctime, --time=status
List files by status change time (not creation/modification time).
- --color, --colour, --color=yes, --colour=yes
Colorize the names of files depending on the type of file.
- --color=no, --colour=no
Disables colorization. This is the default. Provided to
override a previous color option.
- --color=tty, --colour=tty
Same as --color, but only if standard output is a
terminal. Very useful for shell scripts
and command aliases, especially if your favorite
pager does not support color control codes.
- -d, --directory
Report only on the directory, not its contents.
- -f
Print directory contents in exactly the order in which they are stored,
without attempting to sort them.
- --full-time
List times in full, rather than use the standard
abbreviations.
- --help
Print a help message and then exit.
- -i, --inode
List the inode for each file.
- -k, --kilobytes
If file sizes are being listed, print them in kilobytes. This option overrides
the environment variable POSIXLY_CORRECT.
- -l, --format=long, --format=verbose
Long format listing (includes permissions, owner, size, modification
time, etc.).
- -m, --format=commas
Merge the list into a comma-separated series of names.
- -n, --numeric-uid-gid
Like -l, but use group-ID and user-ID numbers instead of owner and group
names.
- -p
Mark directories by appending / to them.
- -q, --hide-control-chars
Show nonprinting characters as ?.
- -r, --reverse
List files in reverse order (by name or by time).
- -s, --size
Print size of the files in blocks.
- -t, --sort=time
Sort files according to modification time (newest first).
- -u, --time=atime, --time=access, --time=use
Sort files according to the file access time.
- --version
Print version information on standard output, then exit.
- -x, --format=across, --format=horizontal
List files in rows going across the screen.
- -A, --almost-all
List all files, including the normally hidden files whose names begin with
a period. Does not include the . and . directories.
- -B, --ignore-backups
Do not list files ending in ~, unless given as arguments.
- -C, --format=vertical
List files in columns (the default format).
- -F, --classify
Flag filenames by appending / to directories, * to
executable files, @ to symbolic links, | to FIFOs, and = to sockets.
- -G, --no-group
In long format, do not display group name.
- -I, --ignore pattern
Do not list files whose names match the shell pattern
pattern, unless they are given on the command line.
- -L, --dereference
List the file or directory referenced by a symbolic link rather than
the link itself.
- -N, --literal
Do not list filenames.
- -Q, --quote-name
Quote filenames with "; quote nongraphic characters
with alphabetic and octal backslash sequences.
- -R, --recursive
Recursively list subdirectories as well as the specified (or current) directory.
- -S, --sort=size
Sort by file size, largest to smallest.
- -T, --tabsize n_cols
Assume that each tabstop is n_cols columns wide. The
default is 8.
- -U, --sort=none
Do not sort files. Similar to -f but display in long
format.
- -X, --sort=extension
Sort by file extension.
Examples
List all files in the current directory and their sizes; use multiple
columns and mark special files:
ls -asCF
List the status of directories /bin and /etc:
ls -ld /bin /etc
List C source files in the current directory, the oldest first:
ls -rt *.c
Count the nonhidden files in the current directory:
ls | wc -l
|
lsattr | lsattr [options] [files] Print attributes of files on a Linux Second Extended File System.
See also chattr.
Options
- -a
List all files in specified directories.
- -d
List directories' attributes, not the attributes of the contents.
- -R
List directories and their contents recursively.
- -v
List version of files.
- -V
List version and then exit.
|
lsmod | lsmod System administration command.
List all loaded modules: their name, size (in 4KB units)
and, if appropriate, a list of referring modules.
File
- /proc/modules
Source of the same information.
|
m4 | m4 [options] [macros] [files] Macro processor for C and other files.
Options
- -e, --interactive
Operate interactively, ignoring interrupts.
- -dflags, --debug=flags
Specify flag-level debugging.
- -ln, --arglength=n
Specify the length of debugging output.
- -o file, --error-output=file
Place output in file. Despite the name, print error messages
on standard error.
- -p, --prefix-built-ins
Prepend m4_ to all built-in macro names.
- -s, --synclines
Insert #line directives for the C preprocessor.
- -Bn
Set the size of the push-back and argument collection buffers
to n (default is 4096).
- -Dname[=value], --define=name[=value]
Define name as value or, if value is not specified,
define name as null.
- -E, --fatal-warnings
Consider all warnings to be fatal, and exit after the first of them.
- -Ffile, --freeze-state file
Record m4's frozen state in file, for later reloading.
- -G, --traditional
Behave like traditional m4, ignoring GNU extensions.
- -Hn, --hashsize=n
Set symbol-table hash array to n (default is 509).
- -Idirectory, --include=directory
Search directory for include files.
- -Q, --quiet, --silent
Suppress warning messages.
- -Rfile, --reload-state file
Load state from file before starting execution.
- -Uname, --undefine=name
Undefine name.
|
mail | mail [options] [users] Read mail or send mail to other users. The
mail utility allows you to compose,
send, receive, forward, and reply to mail. mail has two main modes: compose mode, in which
you create a message, and command mode, in which you manage your mail.
While mail is a powerful utility, it
can be tricky for a novice user. Most Linux distributions include
pine and elm, which are much easier to use.
This section presents mail
commands, options, and files.
To get you started, here are two of the most basic commands.
To enter interactive mail-reading mode, type:
mail
To begin writing a message to user, type:
mail user
Enter the text of the message, one line at a time, pressing Enter at
the end of each line. To end the message, enter a single period (.)
in the first column of a new line, and press Enter.
Command-line options
- -b list
Set blind carbon copy field to comma-separated list.
- -c list
Set carbon copy field to comma-separated list.
- -d
Print debugging information.
- -f [file]
Process contents of file, instead of
/var/spool/mail/$user. If file is omitted, process mbox in the user's home directory.
- -i
Do not respond to tty interrupt signals.
- -n
Do not consult /etc/mail.rc when starting up.
- -p
Read mail in POP mode.
- -s subject
Set subject to subject.
- -u
Process contents of /var/spool/mail/$user. Default.
- -v
Verbose. Print information about mail delivery to standard out.
- -I
Interactive -- even when standard input has been redirected from the
terminal.
- -N
When printing a mail message or entering a mail folder, do not display
message headers.
- -P
Disable POP mode.
Compose-mode commands
- ~!
Execute a shell escape from compose mode.
- ~?
List compose mode escapes.
- ~b names
Add names to or edit the Bcc: header.
- ~c names
Add names to or edit the Cc: header.
- ~d
Read in the dead.letter file.
- ~e
Invoke text editor.
- ~f messages
Insert messages into message being composed.
- ~F messages
Similar to ~f, but include message headers.
- ~h
Add to or change all the headers interactively.
- ~m messages
Similar to ~f, but indent with a tab.
- ~M messages
Similar to ~m, but include message headers.
- ~p
Print message header fields and message being sent.
- ~q
Abort current message composition.
- ~r filename
Append file to current message.
- ~s string
Change Subject: header to string.
- ~t names
Add names to or edit the To list.
- ~v
Invoke editor specified with the VISUAL environment variable.
- ~| command
Pipe message through command.
- ~: mail-command
Execute mail-command.
- ~~string
Insert string in text of message, prefaced by a single tilde
(~). If string contains a ~, it must be escaped with a \.
Command-mode commands
? |
List summary of commands (help screen). |
! |
Execute a shell command. |
- num |
Print numth previous message; defaults
to immediately previous. |
alias (a) |
Print or create alias lists. |
alternates (alt) |
Specify remote accounts on remote machines that are yours.
Tell mail not to reply to them. |
chdir (c) |
cd to home or specified directory. |
copy (co) |
Similar to save, but do not mark message for deletion. |
delete (d) |
Delete message. |
dp |
Delete current message and display next one. |
edit (e) |
Edit message. |
exit (ex, x) |
Exit mail without updating folder. |
file (fi) |
Switch folders. |
folder (fold) |
Read messages saved in a file. Files can be: |
|
#
Previous |
|
%
System mailbox |
|
%user
user's system mailbox |
|
&
mbox |
|
+folder
File in folder directory. |
folders |
List folders. |
headers (h) |
List message headers at current prompt. |
headers+ (h+) |
Move forward one window of headers. |
headers- (h-) |
Move back one window of headers. |
help |
Same as ?. |
hold (ho) |
Hold messages in system mailbox. |
ignore |
Append list of fields to ignored fields. |
mail user (m) |
Compose message to user. |
mbox |
Default. Move specified messages to mbox on exiting. |
next (n) |
Type next message or next message that matches argument. |
preserve (pr) |
Synonym for hold. |
print [list] (p) |
Display each message in list. |
Print [list] (P) |
Similar to print, but include header fields. |
quit (q) |
Exit mail and update folder. |
reply (r) |
Send mail to all on distribution list. |
Reply (R) |
Send mail to author only. |
respond |
Same as reply. |
retain |
Always include this list of header fields when printing messages. With
no arguments, list retained fields. |
save (s) |
Save message to folder. |
saveignore |
Remove ignored fields when saving. |
saveretain |
Override saveignore to retain specified fields. |
set (se) |
Set or print mail options. |
shell (sh) |
Enter a new shell. |
size |
Print size of each specified message. |
source |
Read commands from specified file. |
top |
Print first few lines of each specified message. |
type (t) |
Same as print. |
Type (T) |
Same as Print. |
unalias |
Discard previously defined aliases. |
undelete (u) |
Restore deleted message. |
unread (U) |
Mark specified messages as unread. |
unset (uns) |
Unset mail options. |
visual (v) |
Edit message with editor specified by the VISUAL environment variable. |
write (w) |
Write message, without header, to file. |
xit (x) |
Same as exit. |
z |
Move mail's attention to next windowful of text. Use z- to move it back. |
mail options
These options are used inside of the .mailrc file. The syntax
is set option or unset option.
append |
Append (do not prepend) messages to mbox. |
ask |
Prompt for subject. |
askbcc |
Prompt for blind carbon copy recipients. |
askcc |
Prompt for carbon copy recipients. |
asksub |
Prompt for Subject line. |
autoprint |
Print next message after a delete. |
chron |
Display messages in chronological order, most recent last. |
debug |
Same as -d on command line. |
dot |
Interpret a solitary . as an EOF. |
folder |
Define directory to hold mail folders. |
hold |
Keep message in system mailbox upon quitting. |
ignore |
Ignore interrupt signals from terminal. Print them as @. |
ignoreeof |
Do not treat ^D as an EOF. |
metoo |
Do not remove sender from groups when mailing to them. |
noheader |
Same as -N on command line. |
nokerberos |
Retrieve POP mail via POP3, not KPOP, protocol. |
nosave |
Do not save aborted letters to dead.letter. |
pop-mail |
Retrieve mail with POP3 protocol, and save it in mbox.pop. |
prompt |
Set prompt to a different string. |
Replyall |
Switch roles of Reply and reply. |
quiet |
Do not print version at startup. |
searchheaders |
When given the specifier /x:y, expand all messages
that
contain the string y in the x header field. |
verbose |
Same as -v on command line. |
verbose-pop |
Display status while retrieving POP mail. |
Special files
calendar |
Contains reminders that the operating system mails to you. |
.maildelivery |
Mail delivery configuration file. |
.mailrc |
Mail configuration file. |
triplog |
Keeps track of your automatic response recipients. |
tripnote |
Contains automatic message. |
|
mailq |
mailq [option] System administration command. List all messages in the sendmail mail queue. Equivalent to sendmail -bp.
Option
- -v
Verbose mode.
|
mailstats |
mailstats [options] System administration command. Display a formatted report of the
current sendmail mail statistics.
Options
- -C file
Use sendmail configuration
file file instead of the default
sendmail.cf file.
- -f file
Use sendmail statistics
file file instead of the file specified in
the sendmail configuration file.
- -o
Don't show the name of the mailer in the report.
|
make | make [options] [targets] [macro definitions] Update one or more targets according to dependency
instructions in a description file in the current directory.
By default, this file is called makefile or Makefile.
Options, targets, and macro definitions can be in any order.
Macros definitions are typed as:
name=string
For more information on make, see
Managing Projects with make by Andrew Oram and Steve Talbott.
Options
- -d, --debug
Print detailed debugging information.
- -e, --environment-overrides
Override makefile macro definitions with environment variables.
- -f makefile, --file=makefile, --makefile=makefile
Use makefile as the description file; a filename of -
denotes standard input.
- -h, --help
Print options to make command.
- -i, --ignore-errors
Ignore command error codes (same as .IGNORE).
- -j [jobs], --jobs [=jobs]
Attempt to execute jobs jobs simultaneously, or, if no number is
specified, as many jobs as possible.
- -k, --keep-going
Abandon the current target when it fails, but keep working with
unrelated targets.
- -l [load], --load-average [=load], --max-load [=load]
Attempt to keep load below load, which should be a
floating-point number. Used with -j.
- -n, --just-print, --dry-run, --recon
Print commands but don't execute (used for testing).
- -o file, --old-file=file, --assume-old=file
Never remake file or cause other files to be remade on account of it.
- -p, --print-data-base
Print rules and variables in addition to normal execution.
- -q, --question
Query; return 0 if file is up-to-date; nonzero otherwise.
- -r, --no-built-in-rules
Do not use default rules.
- -s, --silent, --quiet
Do not display command lines (same as .SILENT).
- -t, --touch
Touch the target files, without remaking them.
- -v, --version
Show version of make.
- -w, --print-directory
Display the current working directory before and after execution.
- --warn -undefined -variables
Print warning if a macro is used without being defined.
- -C directory, --directory directory
cd to directory before beginning make operations.
A subsequent -C directive will cause make to attempt to
cd into a directory relative to the current working
directory.
- -I directory, --include-dir directory
Include directory in list of directories that contain
included files.
- -S, --no-keep-going, --stop
Cancel previous -k options. Useful in recursive makes.
- -W file, --what-if file, --new-file file, --assume-new file
Behave as though file has been recently updated.
Description file lines
Instructions in the description file are interpreted as single lines.
If an instruction must span more than one input line, use a backslash
(\) at the end of the line so that the next line is considered as a
continuation.
The description file may contain any of the following types of lines:
- Blanklines
Blank lines are ignored.
- Commentlines
A pound sign (#) can be used at the beginning of a line or anywhere
in the middle. make ignores everything after the #.
- Dependencylines
Depending on one or more targets, certain commands that follow will be
executed. Possible formats include:
targets : dependencies
targets : dependencies ; command
Subsequent commands are executed if dependency files (the names of which
may contain wildcards) do not
exist or are newer than a target. If no prerequisites are supplied,
then subsequent commands are always executed
(whenever any of the targets are specified). No tab should precede any targets.
- Suffixrules
These specify that files ending with the first suffix can be prerequisites for
files ending with the second suffix (assuming the root filenames are the
same). Either of these formats can be used:
.suffix.suffix:
.suffix:
The second form means that the root filename depends on the filename with the
corresponding suffix.
- Commands
Commands are grouped below the dependency line and
are typed on lines that begin with a tab.
If a command is preceded by a hyphen (-), make ignores
any error returned. If a command is preceded by an at sign (@),
the command line won't echo on the display (unless make is called
with -n).
- macrodefinitions
These have the following form:
name = string
or
define name
string
endef
Blank space is optional around the =.
- includestatements
Similar to the C include directive, these have the form:
include files
Internal macros
- $?
The list of prerequisites that have been changed more recently than the
current target. Can be used only in normal description file
entries -- not suffix rules.
- $@
The name of the current target, except in description file entries
for making libraries, where it becomes the library name. Can be used
both in normal description file entries and in suffix rules.
- $<
The name of the current prerequisite that has been modified more recently
than the current target.
- $*
The name -- without the suffix -- of the current prerequisite that has
been modified more recently than the current target. Can be used only in
suffix rules.
- $%
The name of the corresponding .o file when the current target is a
library module. Can be used both in normal description file entries
and in suffix rules.
- $^
A space-separated list of all dependencies, with no duplications.
- $+
A space-separated list of all dependencies, including duplications.
Pattern rules
These are a more general application of the idea behind suffix
rules. If a target and a dependency both contain %, GNU
make will substitute any part of an existing filename. For
instance, the standard suffix rule:
$(cc) -o $@ $<
can be written as the following pattern rule:
%.o : %.c
$(cc) -o $@ $<
Macro modifiers
- D
The directory portion of any internal macro name except
$?. Valid uses are:
$(*D) $$(@D) $(?D) $(<D)
$(%D) $(@D) $(^D)
- F
The file portion of any internal macro name except $?.
Valid uses are:
$(*F) $$(@F) $(?F) $(<F)
$(%F) $(@F) $(^F)
Functions
- $(subst from, to, string)
Replace all occurrences of from with to in string.
- $(patsubst pattern, to, string)
Similar to subst, but treat % as a wildcard within
pattern. Substitute to for any word in string that
matches pattern.
- $(strip string)
Remove all extraneous whitespace.
- $(findstring substring, mainstring)
Return substring if it exists within mainstring; otherwise,
return null.
- $(filter pattern, string)
Return those words in string that match at least one word in
pattern. patterns may include the wildcard %.
- $(filter-out pattern, string)
Remove those words in string that match at least one word in
pattern. patterns may include the wildcard %.
- $(sort list)
Return list, sorted in lexical order.
- $(dir list)
Return the directory part (everything up to the last slash) of each
filename in list.
- $(notdir list)
Return the nondirectory part (everything after the last slash) of each
filename in list.
- $(suffix list)
Return the suffix part (everything after the last period) of each
filename in list.
- $(basename list)
Return everything but the suffix part (everything up to the last
period) of each filename in list.
- $(addsuffix suffix,list)
Return each filename given in list with suffix appended.
- $(addprefix prefix,list)
Return each filename given in list with prefix prepended.
- $(join list1,list2)
Return a list formed by concatenating the two arguments, word by
word (e.g., $(join a b,.c .o) becomes a.c b.o).
- $(word n,string)
Return the nth word of string.
- $(words string)
Return the number of words in string.
- $(firstword list)
Return the first word in the list list.
- $(wildcard pattern)
Return a list of existing files in the current directory that match
pattern.
- $(origin variable)
Return one of the following strings that describes how variable
was defined: undefined, default, environment,
environment override, file, command line, override, or automatic.
- $(shell command)
Return the results of command. Any newlines in the result are
to be converted to spaces. This function works similarly to backquotes in
most shells.
Macro string substitution
- $(macro:s1=s2)
Evaluates to the current definition of $(macro),
after substituting the string s2 for every occurrence of s1
that occurs either immediately before a blank or tab or at the end of
the macro definition.
Special target names
- .DEFAULT:
Commands associated with this target are executed if make
can't find any description file entries or suffix rules with which to build a
requested target.
- .EXPORT_ALL_VARIABLES:
If this target exists, export all macros to all child processes.
- .IGNORE:
Ignore error codes. Same as the -i option.
- .PHONY:
Always execute commands under a target, even if it is an existing,
up-to-date file.
- .PRECIOUS:
Files you specify for this target are not removed
when you send a signal (such as an interrupt) that aborts make
or when a command line in your description file returns an error.
- .SILENT:
Execute commands, but do not echo them. Same as the -s option.
- .SUFFIXES:
Suffixes associated with this target are meaningful in suffix rules.
If no suffixes are listed, the existing list of suffix rules is
effectively "turned off."
|
makedbm | makedbm [options] infile outfile NFS/NIS command. Make NIS dbm file. makedbm takes infile and converts it
to a pair of files in ndbm format, namely outfile.pag and
outfile.dir. Each line of the input file is converted to a single
dbm record. All characters up to the first TAB or SPACE form the
key, and the rest of the line is the data. If line ends with \&,
the data for that record is continued on to the next line. It is
left for the NIS clients to interpret #; makedbm does not treat
it as a comment character. infile can be -, in which case the
standard input is read.
makedbm generates a special entry with the key
yp_last_modified, which is the date of infile (or the
current time, if infile is -).
Options
- -b
Interdomain. Propagate a map to all servers using the interdomain
name server named.
- -d yp_domain_name
Create a special entry with the key yp_domain_name.
- -i yp_input_file
Create a special entry with the key yp_input_file.
- -l
Convert keys of the given map to lowercase.
- -m yp_master_name
Create a special entry with the key yp_master_name. If no master
hostname is specified, yp_master_name is set to the local hostname.
- -o yp_output_file
Create a special entry with the key yp_output_name.
- -s
Secure map. Accept connections from secure NIS networks only.
- -u dbm filename
Undo a dbm file -- print out a dbm file, one entry per
line, with a single space separating keys from values.
Example
It is easy to write shell scripts to convert standard files such as
/etc/passwd to the key value form used by makedbm. For example,
the awk program:
BEGIN { FS =":";OFS = "\t";}
{ print $1, $0}
takes the /etc/passwd file and converts it to a form that can
be read by makdbm to make the NIS file passwd.byname. That is,
the key is a username and the value is the remaining line in the
/etc/passwd file.
|
makemap |
makemap [options] type name System administration command.
Transfer from standard input to sendmail's database maps.
Input should be formatted as:
key value
You may comment lines with #, may substitute parameters with
%n, and must escape literal % by entering it as %%.
The type must be dbm, btree, or
hash. The name is a filename to which makemap
appends standard suffixes.
Options
- -d
Allow duplicate entries. Valid only with btree type maps.
- -f
Suppress conversion of uppercase to lowercase.
- -N
Append a zero byte to each key.
- -o
Append to existing file instead of replacing it.
- -r
If some keys already exist, replace them. (By default, makemap
will exit when encountering a duplicated key.)
- -s
Ignore safety checks.
- -v
Verbose mode.
|
man | man [options] [section] [title]
Display information from the online reference manuals.
man locates and
prints the named title from the
designated reference section.
Options
- -7, --ascii
Expect a pure ASCII file, and format it for a 7-bit
terminal or terminal emulator.
- -a, --all
Show all pages matching title.
- -b
Leave blank lines in output.
- -d, --debug
Display debugging information. Suppress actual printing of manual pages.
- -f, --whatis
Same as whatis command.
- -k, --apropos
Same as apropos command.
- -l, --local-file
Search local files, not system files, for manual pages. If i is given
as filename, search standard input.
- -m systems, --systems=systems
Search systems' manual pages. systems should be a
comma-separated list.
- -p preprocessors, --preprocessor=preprocessors
Preprocess manual pages with preprocessors before turning them
over to nroff, troff, or groff. Always runs soelim first.
- -r prompt, --prompt=prompt
Set prompt if less is used as pager.
- -t, --troff
Format the manual page with /usr/bin/groff -Tgv -mandoc. Implied by
-T and -Z.
- -u, --update
Perform a consistency check between manual page cache and filesystem.
- -w, --where, --location
Print pathnames of entries on standard output.
- -D, --default
Reset all options to their defaults.
- -L locale, --locale=locale
Assume current locale to be locale; do not consult the
setlocale() function.
- -M path, --manpath=path
Search for manual pages in path. Ignore -m option.
- -Ppager, --pager=pager
Select paging program pager to display the entry.
- -T device, --troff-device[=device]
Format groff or troff output for device, such as
dvi, latin1, X75, and X100.
- -Z, --ditroff
Do not allow postprocessing of manual page after groff has finished
formatting it.
Section names
Manual pages are divided into sections, depending on their intended
audience:
- 1
Executable programs or shell commands
- 2
System calls (functions provided by the kernel)
- 3
Library calls (functions within system libraries)
- 4
Special files (usually found in /dev)
- 5
File formats and conventions (e.g., /etc/passwd)
- 6
Games
- 7
Macro packages and conventions
- 8
System administration commands (usually only for a privileged user)
- 9
Kernel routines (nonstandard)
|
manpath | manpath [options] Attempt to determine path to manual pages. Check $MANPATH first; if that
is not set, consult /etc/man.conf,
user environment variables, and the current working directory. The
manpath command is a symbolic link
to man, but
most of the options are ignored for manpath.
Options
- -d, --debug
Print debugging information.
- -h
Print help message and then exit.
|
merge | merge [options] file1 file2 file3 Perform a three-way file merge.
merge incorporates all changes that
lead from file2 to file3
and puts the results into file1.
merge is
useful for combining separate changes to an original. Suppose
file2 is the original, and both
file1 and file3 are
modifications of file2. Then
merge combines both
changes. A conflict occurs if both file1 and
file3 have
changes in a common segment of lines. If a conflict is
found, merge normally outputs a warning and puts brackets around the
conflict, with lines preceded by <<<<<<< and >>>>>>>.
A typical conflict looks like this:
<<<<<<< file1
relevant lines from file1
=======
relevant lines from file3
>>>>>>> file3
If there are conflicts, the user should edit the result
and delete one of the alternatives.
Options
- -e
Don't warn about conflicts.
- -p
Send results to standard output instead of overwriting
file1.
- -q
Quiet; do not warn about conflicts.
- -A
Output conflicts using the -A style of
diff3. This merges all changes
leading from file2 to file3 into
file1 and generates the most verbose output.
- -E
Output conflict information in a less verbose style
than -A; this is the default.
- -L label
Specify up to three labels to be used in place of the corresponding
filenames in conflict reports. That is:
merge -L x -L y -L z file_a file_b file_c
generates output that looks as if it came from x,
y, and z instead of
from file_a, file_b, and
file_c.
- -V
Print version number.
|
mesg | mesg [option] Change the ability of other users to send write messages
to your terminal. With no options, display the permission
status.
Options
- n
Forbid write messages.
- y
Allow write messages (the default).
|
mimencode | mimencode [options] [filename] [-o output_file] mimencode [options] [filename] [-o output_file] Translate to and from MIME encoding formats,
the proposed standard for Internet multimedia mail formats.
By default, mimencode reads standard input and sends a
base64-encoded version of the input to standard output.
Options
- -b
Use the (default) base64 encoding.
- -o output_file
Send output to the named file rather than to standard output.
- -p
Translate decoded CRLF sequences into the local newline
convention during decoding and do the reverse during
encoding; meaningful only when the default base64 encoding is
in effect.
- -q
Use the quoted-printable encoding instead of base64.
- -u
Decode the standard input rather than encode it.
|
mkdir | mkdir [options] directories Create one or more directories. You must have write
permission in the parent directory in order to create a
directory. See also rmdir. The default mode of
the new directory is 0777, modified by the system or user's
umask.
Options
- -m, --mode mode
Set the access mode for new directories. See
chmod for an explanation
of acceptable formats for mode.
- -p, --parents
Create intervening parent directories if they don't exist.
- --verbose
Print a message for each directory created.
- --help
Print help message and then exit.
- --version
Print version number and then exit.
Examples
Create a read-only directory named personal:
mkdir -m 444 personal
The following sequence:
mkdir work; cd work
mkdir junk; cd junk
mkdir questions; cd ../..
can be accomplished by typing this:
mkdir -p work/junk/questions
|
mke2fs | mke2fs [options] device [blocks] mkfs.ext2 [options] device [blocks] System administration command.
Format device as a Linux Second Extended Filesystem.
You may specify the number of blocks on the device or allow
mke2fs to guess.
Options
- -b block-size
Specify block size in bytes.
- -c
Scan device for bad blocks before execution.
- -f fragment-size
Specify fragment size in bytes.
- -i bytes-per-inode
Create an inode for each bytes-per-inode of space.
bytes-per-inode must be 1024 or greater; it is
4096 by default.
- -l filename
Consult filename for a list of bad blocks.
- -m percentage
Reserve percentage percent of the blocks for use by
privileged users.
- -q
Quiet mode.
- -v
Verbose mode.
- -S
Write only superblock and group descriptors; suppress writing
of inode table and block and inode bitmaps.
Useful only when attempting to salvage damaged
systems.
|
mkfs | mkfs [options] [fs-options] filesys [blocks] System administration command.
Construct a filesystem on a device (such as a hard disk partition).
filesys is either the name of the device or the mountpoint.
mkfs is actually a frontend that
invokes the appropriate version of mkfs according to a
filesystem type specified by the -t option. For example,
a Linux Second Extended Filesystem uses mkfs.ext2 (which is the
same as mke2fs); MS-DOS filesystems use mkfs.msdos.
fs-options are options specific to the filesystem type.
blocks is the size of the filesystem in 1024-byte blocks.
Options
- -V
Produce verbose output, including all commands executed to create
the specific filesystem.
- -t fs-type
Tells mkfs what type of filesystem to construct.
- filesystem-specific options
These options must follow generic
options and not be combined with them. Most filesystem builders
support these three options:
- -c
Check for bad blocks on the device before building the filesystem.
- -l file
Read the file file for the list of bad blocks on the device.
- -v
Produce verbose ouput.
|
mkfs.minix | mkfs.minix [options] device size System administration command.
Creates a MINIX filesystem. See mkfs.
|
mklost+found | mklost+found System administration command.
Create a lost+found directory in the current working
directory. Intended for Linux Second Extended Filesystems.
|
mkraid |
mkraid [options] devices System administration command. Set up RAID array
devices as defined in the
/etc/raidtab configuration file. mkraid can be used to initialize a new array or
upgrade older RAID device arrays for the new kernel. Initialization
will destroy any data on the disk devices used to create the array.
Options
- -c file,
--configfile file
Use file instead of /etc/raidtab.
- -f, --force
Initialize the devices used to create the RAID array even if
they currently have data.
- -h,
--help
Print a usage message and then exit.
- -o,
--upgrade
Upgrade an older array to the current kernel's RAID version. Preserve data on the old array.
- -V,
--version
Print version information and then exit.
|
mkswap | mkswap [option] device [size] System administration command.
Create swap space on device. You may specify its size
in blocks; each block is a page of about 4KB.
Option
- -c
Check for bad blocks before creating the swap space.
|
modprobe | modprobe [options] [modules] System administration command.
With no options, attempt to load the specified module, as
well as all modules on which it depends. If more than one
module is specified,
attempt to load further modules only
if the previous module failed to load.
Options
- -a
Load all listed modules, not just the first one.
- -l [pattern]
List all existing modules. This option may be combined with
-t to specify a type of module, or you may include a
pattern to search for.
- -r
Remove the specified modules, as well as the modules on
which they depend.
- -t type
Load only a specific type of module. Consult /etc/conf.modules
for the directories in which all modules of that type reside.
Files
- /etc/conf.modules
Information about modules: which ones depend on others,
which directories correspond to particular types of
modules.
- /sbin/insmod, /sbin/rmmod, /sbin/depmod
Programs that modprobe relies on.
|
more | more [options] [files] Display the named files on a terminal, one screenful at a time.
See less for an alternative to more.
Some commands can be preceded by a number.
Options
- +num
Begin displaying at line number num.
- -num number
Set screen size to number lines.
- +/pattern
Begin displaying two lines before pattern.
- -c
Repaint screen from top instead of scrolling.
- -d
Display the prompt "Hit space to continue, Del to abort" in response to
illegal commands; disable bell.
- -f
Count logical rather than screen lines. Useful when long lines wrap
past the width of the screen.
- -l
Ignore form-feed (Ctrl-L) characters.
- -p
Page through the file by clearing each window instead of scrolling. This is sometimes faster.
- -r
Force display of control characters, in the form ^x.
- -s
Squeeze; display multiple blank lines as one.
- -u
Suppress underline characters.
Commands
All commands in more are based on
vi commands. An argument
can precede many commands.
- SPACE
Display next screen of text.
- z
Display next lines of text, and redefine a screenful to
lines lines. Default is one screenful.
- RETURN
Display next lines of text, and redefine a screenful to
lines lines. Default is one line.
- d, ^D
Scroll lines of text, and redefine scroll size to
lines lines. Default is one line.
- q, Q, INTERRUPT
Quit.
- s
Skip forward one line of text.
- f
Skip forward one screen of text.
- b, ^B
Skip backward one screen of text.
- '
Return to point where previous search began.
- =
Print number of current line.
- /pattern
Search for pattern, skipping to
numth occurrence if an argument is specified.
- n
Repeat last search, skipping to numth
occurrence if an argument is specified.
- !cmd, :!cmd
Invoke shell and execute cmd in it.
- v
Invoke vi editor on the file, at the
current line.
- ^L
Redraw screen.
- :n
Skip to next file.
- :p
Skip to previous file.
- :f
Print current filename and line number.
- .
Reexecute previous command.
Examples
Page through file in "clear" mode, and display prompts:
more -cd file
Format doc to the screen, removing underlines:
nroff doc | more -u
View the manpage for the grep command; begin near the word "BUGS"
and compress extra whitespace:
man grep | more +/BUGS -s
|
mount | mount [options] [special-device] [directory] System administration command.
Mount a file structure. mount announces to the system that a
removable file structure is present on special-device. The file
structure is mounted on directory, which must already
exist and should be empty; it then becomes the name of the root of the newly
mounted file structure. If mount is invoked with no
arguments, it displays the name of each mounted device, the directory
on which it is mounted, whether the file structure is read-only, and
the date it was mounted. Only a privileged user can use the
mount command.
Options
- -a
Mount all filesystems listed in /etc/fstab.
Note: this is the only option that cannot take a
special-device or node argument.
- -f
Fake mount. Go through the motions of checking the device and directory, but do not actually mount the filesystem.
- -n
Do not record the mount in /etc/mtab.
- -o option
Note: this is the only option to mount that requires a
special-device or node argument.
Qualify the mount with one of the specified options:
- async
Read input and output to the device asynchronously.
- auto
Allow mounting with the -a option.
- defaults
Use all options' default values (async, auto,
dev, exec, nouser, rw, suid).
- dev
Interpret any special devices that exist on the filesystem.
- exec
Allow binaries to be executed.
- noauto
Do not allow mounting via the -a option.
- nodev
Do not interpret any special devices that exist on the filesystem.
- noexec
Do not allow the execution of binaries on the filesystem.
- nosuid
Do not acknowledge any suid or sgid bits.
- nouser
Only privileged users will have access to the filesystem.
- remount
Expect the filesystem to have already been mounted, and
remount it.
- ro
Allow read-only access to the filesystem.
- rw
Allow read/write access to the filesystem.
- suid
Acknowledge suid and sgid bits.
- sync
Read input and output to the device synchronously.
- user
Allow unprivileged users to mount the filesystem. Note that
the defaults on such a system will be nodev, noexec,
and nosuid, unless otherwise
specified.
- check=relaxed|normal|strict
Specify how strictly to regulate the integration of an
MS-DOS filesystem when mounting it.
- conv=binary|text|auto
Specify method by which to convert files on MS-DOS and ISO 9660
filesystems.
- debug
Turn debugging on for MS-DOS and ext2fs filesystems.
- errors=continue|remount|ro|panic
Specify action to take when encountering an error.
ext2fs filesystems only.
- -r
Mount filesystem read-only.
- -t type
Specify the filesystem type. Possible values are:
minix, ext, ext2, xiafs, hpfs,
msdos, umsdos, vfat, proc, nfs, iso9660,
smbfs, ncpfs, affs, ufs, romfs,
sysv, xenix, and coherent. Note that ext and
xiafs are
valid only for kernels older than 2.1.21 and that sysv should be
used instead of xenix and coherent.
- -v
Display mount information verbosely.
- -w
Mount filesystem read/write. This is the default.
Files
- /etc/fstab
List of filesystems to be mounted and options to use when mounting
them.
- /etc/mtab
List of filesystems that are currently mounted and the options
with which they were mounted.
|
mountd | rpc.mountd [options] NFS/NIS command. NFS mount request server. mountd reads the file
/etc/exports to determine which
filesystems are available for mounting by which machines. It also
provides information as to what filesystems are mounted by which
clients. See also nfsd.
Options
- -d, --debug
Debug mode. Output all debugging information via syslogd.
- -f file, --exports-file file
Read the export permissions from file instead of /etc/exports.
- -n, --allow-non-root
Accept even those mount requests that enter via a non-reserved port.
- -p, --promiscuous
Accept requests from any host that sends them.
- -r, --re-export
Allow re-exportation of imported filesystems.
- -v, --version
Print the version number.
File
- /etc/exports
Information about mount permissions.
|
mv | mv [option] sources target Move or rename files and directories.
The source (first column) and target (second column) determine the
result (third column):
Source |
Target |
Result |
File |
name (nonexistent) |
Rename file to name. |
File |
Existing file |
Overwrite existing file with source file. |
Directory |
name (nonexistent) |
Rename directory to name. |
Directory |
Existing directory |
Move directory to be a subdirectory of existing directory. |
One or more files |
Existing directory |
Move files to directory. |
Options
- -b, --backup
Back up files before removing.
- -f, --force
Force the move, even if target file exists;
suppress messages about restricted access modes.
- --help
Print a help message and then exit.
- -i, --interactive
Query user before removing files.
- -u, --update
Do not remove a file or link if its modification date is the same as
or newer than that of its replacement.
- -v, --verbose
Print the name of each file before moving it.
- --version
Print version information and then exit.
- -S suffix, --suffix=suffix
Override the SIMPLE_BACKUP_SUFFIX environment variable,
which determines the suffix used for making simple
backup files. If the suffix is not set either way, the default
is a tilde (~).
- -V value, --version-control=value
Override the VERSION_CONTROL environment variable, which
determines the type of backups made.
The acceptable values for version control are:
- t, numbered
Always make numbered backups.
- nil, existing
Make numbered backups of files that already
have them, simple backups of the others. The default.
- never, simple
Always make simple backups.
|
named | named [options] TCP/IP command. Internet domain name server. named is used by resolver
libraries to provide access to the Internet distributed naming
database. With no arguments, named reads
/etc/named.boot for any initial data and listens for
queries on a privileged port. See RFC 1034 and RFC 1035 for more
details.
There are several
named binaries available at different
Linux archives, displaying various behaviors. If your version doesn't
behave like the one described here, never fear -- it should have come
with documentation.
Options
- -d debuglevel
Print debugging information. debuglevel is a number indicating
the level of messages printed.
- -p port
Use port as the port number. Default is 42.
- [-b] bootfile
File to use instead of named.boot. The -b is optional and
allows you to specify a filename that begins with a leading dash.
File
- /etc/named.boot
Read when named starts up.
|
namei | namei [options] pathname [pathname . . .] Follow a pathname until a terminal point is found (e.g.,
a file, directory, char device, etc.). If
namei finds a
symbolic link, it shows the link and starts following it,
indenting the output to show the context.
namei prints an informative message when
the maximum number of symbolic links this system can have has been exceeded.
Options
- -m
Show the mode bits of each file type in the style
of ls; for example: "rwxr-xr-x".
- -x
Show mountpoint directories with a D,
rather than a d.
File type characters
For each line of output, namei prints the
following characters to identify the file types found:
- -
A regular file
- ?
An error of some kind
- b
A block device
- c
A character device
- d
A directory
- f:
The pathname namei is
currently trying to resolve
- l
A symbolic link (both the link and its contents are output)
- s
A socket
|
netdate | netdate [options] [protocol] hostname... TCP/IP command. Set the system time according to the time provided by
one of the hosts in the list hostname. netdate
tries to ascertain which host is the most reliable
source. When run by an unprivileged user, netdate reports
the current time, without attempting to set the system clock.
You may specify the protocol -- udp (the default)
or tcp -- once, or several times for various hosts.
Options
- -l time
The most reliable host is chosen from the list by sorting
the hosts into groups based on the times they return when
questioned. The first host from the largest group is then
polled a second time. The differences between its time
and the local host's time on each poll are recorded. These
two differences are then compared. If the gap between them is greater
than time (the default is five seconds), the host is
rejected as inaccurate.
- -v
Display the groups into which hosts are sorted.
|
netstat | netstat [options] TCP/IP command. Show network status. For all active sockets,
print the protocol, the number of bytes waiting to be received, the
number of bytes to be sent, the port number, the remote
address and port, and the state of the socket.
Options
- -a
Show the state of all sockets, not just active ones.
- -c
Display information continuously, refreshing once every second.
- -i
Include statistics for network devices.
- -n
Show network addresses as numbers.
- -o
Include additional information such as username.
- -r
Show routing tables.
- -t
List only TCP sockets.
- -u
List only UDP sockets.
- -v
Print the version number and exit.
- -w
List only raw sockets.
- -x
List only Unix domain sockets.
|
newgrp | newgrp [group] Change user's group identification to the specified group. If no group
is specified, change to the user's login group. The new group is then used
for checking permissions.
|
newusers |
newusers file System administration command. Create or update system users from
entries in file. Each line in
file has the same format as an entry in
/etc/passwd, except passwords are unencrypted,
and group IDs can be given as a name or number. During an update, the
password age field is ignored if the user already exists in the
/etc/shadow password file. If a group name or ID
does not already exist, it will be created. If a home directory does
not exist, it will be created.
|
nfsd | rpc.nfsd [options] System administration command.
Daemon that starts the NFS server daemons that handle
client filesystem requests. These daemons are user-level
processes. The options are exactly the same as in
mountd.
|
nice | nice [option] [command [arguments]] Execute a command (with its
arguments) with lower priority
(i.e., be "nice" to other users).
With no arguments, nice prints
the default scheduling priority (niceness).
If nice is a
child process, it prints the parent process's scheduling
priority. Niceness
has a range of -20 (highest priority) to 19
(lowest priority).
Options
- --help
Print a help message and then exit.
- -n adjustment, -adjustment, --adjustment=adjustment
Run command with niceness incremented by adjustment
(1-19); default is 10. A privileged user can raise
priority by specifying a negative adjustment (e.g., -5).
- --version
Print version information and then exit.
|
nm | nm [options] [objfiles] Print the symbol table (name list) in alphabetical order for one or
more object files. If no object files are specified, perform
operations on a.out. Output includes each symbol's value, type,
size, name, and so on. A key letter categorizing the symbol can also be
displayed. If no object file is given, use a.out.
Options
- -a, --debug-syms
Print debugger symbols.
- -f format
Specify output format (bsd, sysv, or posix).
Default is bsd.
- -g, --extern-only
Print external symbols only.
- -n, -v, --numeric-sort
Sort the external symbols by address.
- -p, --no-sort
Don't sort the symbols at all.
- -r, --reverse-sort
Sort in reverse, alphabetically or numerically.
- --size-sort
Sort by size.
- -u, --undefined-only
Report only the undefined symbols.
- -A, -o, -print-file-name
Print input filenames before each symbol.
- -C, --demangle
Translate low-level symbol names into readable versions.
- -D, --dynamic
Print dynamic, not normal, symbols. Useful only when working with
dynamic objects (some kinds of shared libraries, for example).
- -P, --portability
Same as -f posix.
- -V, --version
Print nm's version number on standard error.
|
nohup | nohup command [arguments] Run the named command with its optional command
arguments, continuing to run it even
after you log out (make command immune to hangups;
i.e., no hangup).
TTY output is appended to the file nohup.out by default.
Modern shells preserve background commands by default; this command is
necessary only in the original Bourne shell.
|
nslookup | nslookup [-option...] [host_to_find | - [server ]] TCP/IP command. Query Internet domain name servers.
nslookup has two
modes: interactive and noninteractive. Interactive mode allows the
user to query name servers for information about various hosts and
domains or to print a list of hosts in a domain. It is entered either when
no arguments are given (default name server will be used) or
when the first argument is a hyphen and the second argument is the
hostname or Internet address of a name server. Noninteractive mode is
used to print just the name and requested information for a host or
domain. It is used when the name of the host to be looked up is given
as the first argument. Any of the keyword=value pairs listed
under the interactive set command can be used as an option on the
command line by prefacing the keyword with a -. The optional second
argument specifies a name server.
Options
All of the options under the set interactive command can
be
entered on the command line, with the syntax
-keyword[=value].
Interactive commands
- exit
Exit nslookup.
- finger [name] [>|>>filename]
Connect with finger server on current host, optionally creating or
appending to filename.
- help, ?
Print a brief summary of commands.
- host [server]
Look up information for host using the current default server or
using server if specified.
- ls -[ahd] domain [>|>>filename]
List information available for domain, optionally creating or
appending to filename. The -a option lists aliases of
hosts in the domain. -h lists CPU and operating system
information for the domain. -d lists all contents of a zone
transfer.
- lserver domain
Change the default server to domain. Use the initial server to
look up information about domain.
- root
Change default server to the server for the root of the domain namespace.
- server domain
Change the default server to domain. Use the current default
server to look up information about domain.
- set keyword[=value]
Change state information affecting the lookups. Valid keywords are:
- all
Print the current values of the frequently used options to set.
- class=name
Set query class to IN (Internet), CHAOS, HESIOD, or ANY. Default
is IN.
- domain=name
Change default domain name to name.
- [no]debug
Turn debugging mode on or off.
- [no]d2
Turn exhaustive debugging mode on or off.
- [no]defname
Append default domain name to every lookup.
- [no]ignoretc
Ignore truncate error.
- [no]recurse
Tell name server to query or not query other servers if it does not have the
information.
- [no]search
With defname, search for each name in parent domains of
current domain.
- [no]vc
Always use a virtual circuit when sending requests to the server.
- port=port
Connect to name server using port.
- querytype=value
See type=value.
- retry=number
Set number of retries to number.
- root=host
Change name of root server to host.
- srchlist=domain
Set search list to domain.
- timeout=number
Change timeout interval for waiting for a reply to number
seconds.
- type=value
Change type of information returned from a query to one of:
A |
Host's Internet address |
ANY |
Any available information |
CNAME |
Canonical name for an alias |
HINFO |
Host CPU and operating system |
|
type |
MD |
Mail destination |
MG |
Mail group member |
MINFO |
Mailbox or mail list |
|
information |
MR |
Mail rename domain name |
MX |
Mail exchanger |
NS |
Nameserver for the named zone |
PTR |
Hostname or pointer to other |
|
information |
SOA |
Domain start-of-authority |
TXT |
Text information |
UINFO |
User information |
WKS |
Supported well-known services |
- view filename
Sort and list output of previous ls command(s)
with more.
|
passwd | passwd [user] Create or change a password associated with a user name.
Only the owner or a privileged user may change a password. Owners
need not specify their user name.
|
paste | paste [options] files Merge corresponding lines of one or more files into
tab-
separated vertical columns.
See also cut, join, and pr.
Options
- -
Replace a filename with the standard input.
- -dchar, --delimiters=char
Separate columns with char instead of a tab.
Note: you can separate columns with different characters
by supplying more than one char.
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
- -s, --serial
Merge lines from one file at a time.
Examples
Create a three-column file from files
x, y, and z:
paste x y z > file
List users in two columns:
who | paste - -
Merge each pair of lines into one line:
paste -s -d"\t\n" list
|
patch | patch [options] [original [patchfile]] Apply the patches specified in patchfile to original.
Replace the original with the new, patched version; move the original
to original.orig or original~.
Options
- + [options] [original2]
Apply patches again, with different options or a different original
file.
- -b, --backup
Back up the original file.
- -z suffix, --suffix=suffix
Back up the original file in original.suffix.
- -B prefix, --prefix=prefix
Prepend prefix to the backup filename.
- -c, --context
Interpret patchfile as a context diff.
- -d dir, --directory=dir
cd to directory before beginning patch operations.
- -D string, --ifdef=string
Mark all changes with:
#ifdef
string
#endif
- -e, --ed
Treat the contents of patchfile as ed commands.
- -E, --remove-empty-files
If patch creates any empty files, delete them.
- -f, --force
Force all changes, even those that look incorrect. Skip patches if the original file does not exist;
force patches for files with the wrong version specified;
assume patches are never reversed.
- -i file, --input=file
Read patch from file instead of stdin.
- -t, --batch
Skip patches if the original file does not exist.
- -F num, --fuzz=num
Specify the maximum number of lines that may be ignored
(fuzzed over) when deciding where to install a hunk of code. The default is 2. Meaningful only with context diffs.
- -l, --ignore-whitespace
Ignore whitespace while pattern matching.
- -n, --normal
Interpret patch file as a normal diff.
- -N, --forward
Ignore patches that appear to be reversed or to have already been
applied.
- -o file, --output=file
Print output to file.
- -p[num], --strip[=num]
Specify how much of preceding pathname to strip. A
num of 0 strips everything, leaving just the filename.
1 strips the leading /; each higher number after that
strips another directory from the left.
- -r file, --reject-file=file
Place rejects (hunks of the patch file that patch fails to
place within the original file) in file. Default is
original.rej.
- -R, --reverse
Do a reverse patch: attempt to undo the damage done by patching
with the old and new files reversed.
- -s, --silent, --quiet
Suppress commentary.
- -u, --unified
Interpret patch file as a unified context diff.
- -V method, --version-control=method
Specify method for creating backup files (overridden by -B):
- t, numbered
Make numbered backups.
- nil, existing
Back up files according to preexisting backup schemes,
with simple backups as the default. This is patch's
default behavior.
- never, simple
Make simple backups.
Environment variables
- TMPDIR
Specify the directory for temporary files, /tmp by
default.
- SIMPLE_BACKUP_SUFFIX
Suffix to append to backup files instead of .orig or ~.
- VERSION_CONTROL
Specify what method to use in naming backups (see -V).
|
pathchk | pathchk [ option ] filenames Determine validity and portability of filenames. Specifically,
determine if all directories within the path are searchable and if the
length of the filenames is acceptable.
Options
- -p, --portability
Check portability for all POSIX systems.
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
pcnfsd | /usr/sbin/rpc.pcnfsd NFS/NIS command. NFS authentication and print request server.
pcnfsd is an RPC
server that supports ONC clients on PC systems.
pcnfsd reads the configuration
file /etc/pcnfsd.conf,
if present, then services RPC requests directed to program number
150001. This current release of the pcnfsd
daemon (as of this printing) supports both Version 1
and Version 2 of the pcnfsd protocol. Requests serviced by pcnfsd
fall into three categories: authentication,
printing, and other. Only
the authentication and printing services have administrative
significance.
Authentication
When pcnfsd receives a PCNFSD_AUTH or PCNFSD2_AUTH request, it will log in the user by validating the username and
password, returning the corresponding user ID, group IDs, home directory, and
umask. At this time, pcnfsd will also append a record to the
wtmp database. If you do not want to record PC logins in this
way, add the line:
wtmp off
to the /etc/pcnfsd.conf file.
Printing
pcnfsd supports a printing model based on the use of NFS to
transfer the actual print data from the client to the server. The
client system issues a PCNFSD_PR_INIT or PCNFSD2_PR_INIT
request, and the server returns the path to a spool directory that the
client may use and that is exported by NFS. pcnfsd creates a
subdirectory for each of its clients; the parent directory is normally
/usr/spool/pcnfs and the subdirectory is the hostname of the
client system. If you want to use a different parent directory, add the
line:
spooldir path
to the /etc/pcnfsd.conf file. Once a client has mounted the spool
directory and has transferred print data to a file in this directory,
pcnfsd will issue a PCNFSD_PR_START or PCNFSD2_PR_START
request. pcnfsd constructs a command based on the printing
services of the server operating system and executes the command using
the identity of the PC user. Every print request includes the name of
the printer to be used. pcnfsd interprets a printer as either a
destination serviced by the system print spooler or as a virtual
printer. Virtual printers are defined by
the following line in the
/etc/pcnfsd.conf file:
printer name alias-for command
where name is the name of the printer you want to define,
alias-for is the name of a real printer that corresponds to this
printer, and command is a command that will be executed whenever
a file is printed on name.
|
perl | perl A powerful text-processing language that combines many of the
most useful features of shell programs, C, awk, and sed, as
well as adding extended features of its own. For more
information, see Learning Perl by Randal L. Schwartz and
Programming Perl, 2d ed.,
by Larry Wall, Tom Christiansen, and Randal L. Schwartz.
|
pidof | pidof [options] programs Display the process IDs of the listed program or programs.
pidof is actually a symbolic link to killall5.
Options
- -o pids
Omit all processes with the specified process ID. You may list several
process IDs.
- -s
Return a single process ID.
- -x
Also return process IDs of shells running the named scripts.
|
ping | ping [options] host System administration command.
Confirm that a remote host is online and responding. ping is
intended for use in network testing,
measurement, and management. Because of the load it can impose on the
network, it is unwise to use ping during normal operations or
from automated scripts.
Options
- -c count
Stop after sending (and receiving) count ECHO_RESPONSE
packets.
- -d
Set SO_DEBUG option on socket being used.
- -f
Flood ping-output packets as fast as they come back or 100 times
per second, whichever is more. This can be very hard on a network and
should be used with caution; only a privileged user may use this option.
- -i wait
Wait wait seconds between sending each packet. Default is to wait
1 second between each packet. This option is incompatible with the
-f option.
- -l preload
Send preload number of packets as fast as possible before falling
into normal mode of behavior.
- -n
Numeric output only. No attempt will be made to look up symbolic names
for host addresses.
- -p digits
Specify up to 16 pad bytes to fill out packet sent. This is useful
for diagnosing data-dependent problems in a network. digits
are in hex. For example, -p ff will cause the sent packet to be filled with all 1s.
- -q
Quiet output -- nothing is displayed except the summary lines at
startup time and when finished.
- -r
Bypass the normal routing tables and send directly to a host on an
attached network.
- -s packetsize
Specify number of data bytes to be sent. Default is 56, which
translates into 64 ICMP data bytes when combined with the 8 bytes of
ICMP header data.
- -v
Verbose -- list ICMP packets received other than ECHO_RESPONSE.
- -R
Set the IP record route option, which will store the route of the
packet inside the IP header. The contents of the record route will
be printed if the -v option is given, and
will be set on return
packets if the target
host preserves the record route option across
echoes or the -l option is given.
|
pop2d | in.pop2d System administration command.
Allow users to connect to port 109 and request the contents of their
mailbox in /var/spool/mail. pop2d requires a username
and password before providing mail and can serve individual messages.
See also pop3d.
Commands
Each command must be entered on a separate line.
- HELO
Prompt for username and password.
- FOLD
Open /var/spool/mail/$USER.
- HOST
Open /var/spool/pop/$USER.
- READ
Read a message.
- RETR
Retrieve a message.
- ACKS
Save the last message retrieved and move to next message.
- ACKD
Delete the last message retrieved and move to next message.
- NACK
Save the last message retrieved and expect to resend it.
- QUIT
Exit.
|
pop3d | in.pop3d System administration command.
pop3d is a more recent version of pop2d. It behaves
similarly but accepts a slightly different list of commands.
Commands
- USER
Prompt for name.
- PASS
Prompt for password.
- STAT
Display the number of messages in the mailbox and its total size.
- LIST
Display individual messages' sizes.
- DELE
Delete a message.
- NOOP
Perform a null operation.
- LAST
Print the number of the most recently received message that has been read.
- RSET
Reset: clear all deletion marks.
- TOP
Print the first part of a message.
- QUIT
Exit.
|
portmap | rpc.portmap [option] NFS/NIS command. RPC program number to IP port mapper.
portmap is a server
that converts RPC program numbers to IP port numbers. It
must be running in order to make RPC calls. When an RPC server is
started, it tells portmap what port number it is listening to
and what RPC program numbers it is prepared to serve. When a client
wishes to make an RPC call to a given program number, it first
contacts portmap on the server machine to determine the port
number where RPC packets should be sent. portmap must be
the first RPC server started.
Option
- -d
Run portmap in debugging mode. Does not allow portmap to
run as a daemon.
|
powerd | powerd device
System administration command.
Monitor the connection to an uninterruptible power supply,
which the user must specify via device. When power
goes low, signal init to run its powerwait and
powerfail entries; when full power is restored,
signal init to run its powerokwait entries.
|
pppd | pppd [options] [tty] [speed] System administration command.
PPP stands for the Point-to-Point Protocol; it allows datagram
transmission over a serial connection. pppd attempts to
configure tty for PPP (searching in /dev) or, by
default, the controlling terminal. You can also specify a baud
rate of speed.
Options
- asyncmap map
Specify which control characters cannot pass over the line.
map should be a 32-bit hex number, where each bit represents
a character to escape. For example, bit 00000001 represents the character
0x00; bit 80000000 represents the character 0x1f or _.
You may specify multiple characters.
- auth
Require self-authentication by peers before allowing packets to move.
- connect command
Connect as specified by command, which may be a binary or shell command.
- debug, -d
Increment the debugging level.
- defaultroute
Add a new default route in which the peer is the gateway. When the
connection shuts down, remove the route.
- -detach
Operate in the foreground. By default, pppd forks and operates
in the background.
- disconnect command
Close the connection as specified by command, which may be a
binary or shell command.
- domain d
Specify a domain name of d.
- escape character-list
Escape all characters in character-list, which should be a
comma-separated list of hex numbers. You cannot escape 0x20-0x3f or 0x5e.
- file file
Consult file for options.
- lock
Allow only pppd to access the device.
- mru bytes
Refuse packets of more than bytes bytes.
- name name
Specify a machine name for the local system.
- netmask mask
Specify netmask (for example, 255.255.255.0).
- passive, -p
Do not exit if peer does not respond to attempts to initiate a
connection. Instead, wait for a valid packet from the peer.
- silent
Send no packets until after receiving one.
- [local_IP_address]:[remote_IP_address]
Specify the local and/or remote interface IP addresses, as hostnames
or numeric addresses.
Files
- /var/run/pppn.pid
pppd's process ID. The n in pppn.pid is the number
of the PPP interface unit corresponding to this pppd process.
- /etc/ppp/ip-up
Binary or script to be executed when the PPP link becomes active.
- /etc/ppp/ip-down
Binary or script to be executed when the PPP link goes down.
- /etc/ppp/pap-secrets
Contains usernames, passwords, and IP addresses for use in PAP authentication.
- /etc/ppp/options
System defaults. Options in this file are set before the
command-line options.
- ~/.ppprc
The user's default options. These are read before command-line
options but after the system defaults.
- /etc/ppp/options.ttyname
Name of the default serial port.
|
pr | pr [files] Convert a text file or files to a paginated, columned version, with headers.
If - is provided as the filename,
read from standard input.
Options
- +beg_pag[:end-pag], --pages=[beg_pag[:end-pag]
Begin printing on page beg_pag and end on
end-pag if specified.
- -num_cols, --columns=num_cols
Print in num_cols number of columns, balancing the number
of lines in the columns on each page.
- -a, --across
Print columns horizontally, not vertically.
- -c, --show-control-chars
Convert control characters to hat notation (such as ^C) and other unprintable
characters to octal backslash
format.
- -d, --double-space
Double space.
- -e[tab-char[width]], --expand-tabs=[tab-char[width]]
Convert tabs (or tab-chars) to spaces.
If width is specified,
convert tabs to width characters (default is 8).
- -f, -F, --form-feed
Separate pages with form feeds, not newlines.
- -h header, --header=header
Use header for the header instead of the filename.
- -i[out-tab-char[out-tab-width]], --output-tabs[=out-tab-char[out-tab-width]]
Replace spaces with tabs on output. Can specify
alternative tab character (default is tab) and width (default is 8).
- -J, --join-lines
Merge full lines; ignore
-W if set.
- -l lines, --length=lines
Set page length to lines (default 66). If lines is less than
10, omit headers and footers.
- -m, --merge
Print all files, one file per column.
- -n[delimiter[digits]], --number-lines[=delimiter[digits]]
Number columns, or, with the -m
option, number lines. Append delimiter to each
number (default is a tab) and limit
the size of numbers to digits (default is 5).
- -o width, --indent=width
Set left margin to width.
- -r, --no-file-warnings
Continue silently when unable to open an input file.
- -s[delimiter], --separator[=delimiter]
Separate columns with delimiter (default is a tab)
instead of spaces.
- -S[string], --sep-string[=string]
Separate columns with string. Default is a tab with
-J and a space otherwise.
- -t, --omit-header
Suppress headers, footers, and fills at end of pages.
- -T, --omit-pagination
Like -t but also suppress form feeds.
- -v, --show-non-printing
Convert unprintable characters to octal backslash format.
- -w page_width, --width=page_width
Set the page width to page_width characters for
multi-column output. Default is 72.
- -W page_width, --page-width=page_width
Set the page width to always be page_width characters.
Default is 72.
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
praliases |
praliases [option] System administration command. praliases prints the current sendmail mail aliases. (Usually defined in the
/etc/aliases or
/etc/aliases.db file.)
Option
- -f file
Read the aliases from the specified file instead of
sendmail's default alias files.
|
printenv | printenv [variables] Print values of all environment variables
or, optionally, only the specified variables.
|
printf | printf formats [strings] Print strings using the specified formats.
formats can be ordinary text characters, C-language escape
characters, or more commonly, a set of conversion arguments listed here.
Arguments
- %s
Print the next string.
- %n$s
Print the nth string.
- %[-]m[.n]s
Print the next string, using a field that is m characters wide. Optionally, limit the field to print only the first n characters
of string. Strings are right-adjusted unless the left-adjustment flag, -, is specified.
Examples
printf '%s %s\n' "My files are in" $HOME
printf '%-25.15s %s\n' "My files are in" $HOME
|
ps | ps [options] Report on active processes. Note that you do not need to include a
- before options. In options, list arguments
should either be separated by commas or be put in double quotes.
In comparing the amount of output produced, note that
e prints more than
a and l
prints more than f.
Options
- pids
Include only specified processes, which are given in a
comma-delimited list.
- a
List all processes.
- c
Consult task_struct for command name.
- e
Include environment.
- f
"Forest" family tree format.
- h
Suppress header.
- j
Jobs format.
- l
Produce a long listing.
- m
Memory format.
- n
Print user IDs and WCHAN numerically.
- r
Exclude processes that are not running.
- s
Signal format.
- --sortdelimiter[+|-]key[,[+|-]key[,...]]
Similar to O, but designed to protect multiletter sort keys. See
the later list, "Sort keys".
- ttty
Display only processes running on tty.
- u
Include username and start time.
- v
vm format.
- w
Wide format. Don't truncate long lines.
- x
Include processes without an associated terminal.
- O[+|-]key[,[+|-]key[,...]]
Sort processes. (See the following list, "Sort keys.")
- +
Return key to default direction.
- -
Reverse default direction on key.
- S
Include child processes' CPU time and page faults.
Sort keys
- c, cmd
Name of executable.
- C, cmdline
Whole command line.
- f, flags
Flags.
- g, pgrp
Group ID of process.
- G, tpgid
Group ID of associated tty.
- j, cutime
Cumulative user time.
- J, cstime
Cumulative system time.
- k, utime
User time.
- K, stime
System time.
- m, min_flt
Number of minor page faults.
- M, maj_flt
Amount of major page faults.
- n, cmin_flt
Total minor page faults.
- N, cmaj_flt
Total major page faults.
- o, session
Session ID.
- p, pid
Process ID.
- P, ppid
Parent's process ID.
- r, rss
Resident set size.
- R, resident
Resident pages.
- s, size
Kilobytes of memory used.
- S, share
Number of shared pages.
- t, tty
tty.
- T, start_time
Process's start time.
- U, uid
User ID.
- u, user
User's name.
- v, vsize
Bytes of VM used.
- y, priority
Kernel's scheduling priority.
Fields
- PRI
Process's scheduling priority. A higher number indicates lower
priority.
- NI
Process's nice value. A higher number indicates less CPU time.
- SIZE
Size of virtual image.
- RSS
Resident set size (amount of physical memory), in kilobytes.
- WCHAN
Kernel function in which process resides.
- STAT
Status:
- R
Runnable
- T
Stopped
- D
Asleep and not interruptible
- S
Asleep
- Z
Zombie
- W
No resident pages (second field)
- N
Positive nice value (third field)
- TT
Associated tty.
- PAGEIN
Number of major page faults.
- TRS
Size of resident text.
- SWAP
Amount of swap used, in kilobytes.
- SHARE
Shared memory.
|
psupdate | psupdate [mapfile] System administration command.
Update the psupdate database (on some systems /boot/psupdate;
on others, /etc/psdatabase), which contains information
about the kernel image system map file. If no mapfile is specified,
psupdate uses the default (which is either /usr/src/linux/vmlinux
or /usr/src/linux/tools/zSystem, depending on the distribution).
|
pwck | pwck [option] [files] System administration command.
Remove corrupt or duplicate entries in the /etc/passwd
and /etc/shadow files.
pwck will prompt for a "yes" or "no"
before deleting entries. If the user replies "no,"
the program will exit. Alternate passwd and shadow files
can be checked. If correctable errors are found, the user will
be encouraged to run the usermod command.
Option
- -n
Noninteractive mode. Don't prompt for input, and delete
no entries. Return appropriate exit status.
Exit status
- 0
Success.
- 1
Syntax error.
- 2
One or more bad password entries found.
- 3
Could not open password files.
- 4
Could not lock password files.
- 5
Could not write password files.
|
pwconv |
pwconv pwunconv System administration command. Convert unshadowed entries in
/etc/passwd into shadowed entries in the
/etc/shadow file. Replace the encrypted password
in /etc/password with an x. Shadowing passwords
keeps them safe from password cracking programs. pwconv creates additional expiration
information for the /etc/shadow file from entries
in your /etc/login.defs file. If you add new
entries to the /etc/passwd file, you can run
pwconv again to transfer the new
information to /etc/shadow. Already shadowed
entries are ignored. pwunconv
restores the encrypted passwords to your
/etc/passwd file and removes the
/etc/shadow file. Some expiration information is
lost in the conversion.
|
pwd | pwd Print the full pathname of the current working directory.
See also the dirs shell command, built in
to both bash and
csh/tcsh.
|
quota | quota [options] [user|group] Display disk usage and total space allowed for a designated
user or group. With no argument, the quota for the current user
is displayed. This command reports quotas for all filesystems
listed in /etc/fstab.
Options
- -g
Given with a user argument, display the quotas for the
groups of which the user is a member, instead of the user's quotas.
- -q
Display information only for filesystems in which the user is over quota.
- -u
The default behavior. When used with -g,
display both user and group quota information.
- -v
Display quotas for filesystems even if no storage is currently
allocated.
|
raidstart |
raidstart [options] [devices] raidstop [options] [devices] System administration command. Start or stop RAID
devices as defined in the RAID configuration
file, /etc/raidtab. If option -a (or --all) is used, no
devices need to be given; the command will be
applied to all the devices defined in the configuration file.
Options
- -a,
--all
Apply command to all devices defined in the RAID configuration file.
- -c file,
--configfile file
Use file instead of /etc/raidtab.
- -h,
--help
Print usage message and exit.
- -V,
--version
Print version and exit.
|
ramsize | ramsize [option] [image [size [offset]]] System administration command.
If no options are specified, print usage information for the RAM disk.
The pair of bytes at offset 504 in the kernel image normally specify
the RAM size; with a kernel image argument, print the information
found at that offset. To change that information, specify a new size
(in kilobytes). You may also specify a different offset.
Note that rdev -r is the same as ramsize.
Option
- -o offset
Same as specifying an offset as an argument.
|
ranlib |
ranlib filename Generate an index for archive file filename.
Same as running ar -s.
|
rarp | rarp [options] System administration command.
Administer the Reverse Address Resolution Protocol table
(usually /proc/net/rarp).
Options
- -a [hostname]
Show all entries. If hostname is specified,
show only the entries relevant to hostname, which may be a list.
- -d hostname
Remove the entries relevant to hostname, which may be a list.
- -s hostname hw_addr
Add a new entry for hostname, with the hardware
address hw_addr.
- -t type
Check only for type entries when consulting or changing the
table. type may be ether (the default) or ax25.
- -v
Verbose mode.
|
rcp | rcp [options] file1 file2 rcp [options] file ... directory Copy files between two machines. Each file or
directory
is either a remote filename of the form rname@rhost:path or a
local filename.
Options
- -k
Attempt to get tickets for remote host; query
krb_realmofhost to determine realm.
- -p
Preserve modification times and modes of the source files.
- -r
If any of the source files are directories,
rcp copies each subtree rooted at that name. The destination must be a directory.
- -x
Turns on DES encryption for all data passed by
rcp.
|
rdate | rdate [options] [host...] TCP/IP command. Retrieve the date and time from a
host or hosts on the network and optionally set the local system time.
Options
- -p
Print the retrieved dates.
- -s
Set the local system time from the host; must be specified by
root.
|
rdev | rdev [options] [image [value [offset]]] System administration command.
If no arguments are specified, display a line, in /etc/mtab
syntax, that describes the root filesystem.
Otherwise, change the values of the bytes in the kernel image
that describe the RAM disk size (by default located at decimal byte offset
504 in the kernel), VGA mode (default 506), and root device (default 508).
You must specify the kernel image to change and may specify a new
value and a different offset.
Options
- -o offset
Same as specifying an offset as an argument. The offset is given in decimal.
- -r
Behave like ramsize.
- -s
Behave like swapdev.
- -v
Behave like vidmode.
- -R
Behave like rootflags.
|
rdist | rdist [options] [names] System administration command.
Remote file distribution client program. rdist maintains
identical copies of files over multiple hosts. It reads
commands from a file named distfile to direct the updating
of files and/or directories. An alternative distfile
can be specified with the -f option or the -c option.
Options
- -a num
Do not update filesystems with fewer than num bytes free.
- -c name [login@]host[:dest]
Interpret the arguments as a small distfile, where login
is the user to log in as, host is the destination host,
name is
the local file to transfer, and dest is the remote
name where the file should be installed.
- -d var=value
Define var to have value. This option defines or overrides
variable definitions in the distfile.
Set the variable var to value.
- -f file
Read input from file (by default, distfile).
If file is -, read from standard input.
- -l options
Specify logging options on the local machine.
- -m machine
Update only machine. May be specified multiple times for
multiple machines.
- -n
Suppress normal execution. Instead, print the commands that
would have been executed.
- -ooptions
Specify one or more options, which must be comma-separated.
- chknfs
Suppress operations on files that reside on NFS filesystems.
- chkreadonly
Check filesystem to be sure it is not read-only before attempting
to perform updates.
- chksym
Do not update files that exist on the local host but are symbolic
links on the remote host.
- compare
Compare files; use this comparison rather than age as the criteria for
determining which files should be updated.
- follow
Interpret symbolic links, copying the file to which the link points
instead of creating a link on the remote machine.
- ignlnks
Ignore links that appear to be unresolvable.
- nochkgroup
Do not update a file's group ownership unless the entire file needs updating.
- nochkmode
Do not update file mode unless the entire file needs updating.
- nochkowner
Do not update file ownership unless the entire file needs updating.
- nodescend
Suppress recursive descent into directories.
- noexec
Suppress rdist of executables that are in a.out
format.
- numchkgroup
Check group ownership by group ID instead of by name.
- numchkowner
Check file ownership by user ID instead of by name.
- quiet
Quiet mode; do not print commands as they execute.
- remove
Remove files that exist on the remote host but not the local host.
- savetargets
Save updated files in name.old.
- verify
Print a list of all files on the remote machine that are out
of date, but do not update them.
- whole
Preserve directory structure by creating subdirectories on the
remote machine. For example, if you rdist the file
/foo/bar into the directory /baz, it would produce the
file /baz/foo/bar, instead of the default, /baz/bar.
- younger
Do not update files that are younger than the master files.
- -p path
Specify the path to search for rdistd on the remote machine.
- -t seconds
Specify the timeout period (default 900 seconds) after which rdist
will sever the connection if the remote server has not yet responded.
- -A num
Specify the minimum number of inodes that rdist requires.
- -D
Debugging mode.
- -F
Execute all commands sequentially, without forking.
- -L options
Specify logging options on the remote machine.
- -M num
Do not allow more than num child rdist processes to run
simultaneously. Default is 4.
- -P path
Specify path to rsh on the local machine.
|
rdistd | rdistd options System administration command.
Start the rdist server. Note that you must specify the
-S option, unless you are simply querying for version information
with -V.
Options
- -D
Debugging mode.
- -S
Start the server.
- -V
Display the version number and exit immediately.
|
reboot | reboot [options] System administration command.
Close out filesystems, shut down the system, then reboot the system.
Because this command immediately stops all processes, it
should be run only in single-user mode. If the system is not
in runlevel 0 or 6, reboot calls shutdown -nf.
Options
- -d
Suppress writing to /var/log/wtmp.
- -f
Call reboot even when shutdown would normally be
called.
- -n
Suppress normal call to sync.
- -w
Suppress normal execution; simply write to /var/log/wtmp.
|
renice | renice [priority] [options] [target] Control the scheduling priority of various processes as they run.
May be applied to a process, process group, or user (target).
A privileged user may alter the priority of other users' processes.
priority must, for ordinary users, lie between 0 and the
environment variable PRIO_MAX (normally 20), with a higher number
indicating increased niceness. A privileged user may set a negative
priority, as low as PRIO_MIN, to speed up processes.
Options
- +num
Specify number by which to increase current priority of process, rather
than an absolute priority number.
- -num
Specify number by which to decrease current priority of process, rather
than an absolute priority number.
- -g
Interpret target parameters as process group IDs.
- -p
Interpret target parameters as process IDs (default).
- -u
Interpret target parameters as usernames.
|
reset | reset Clear screen (reset terminal).
|
rev | rev [file] Reverse the lines of a file onto standard output.
The order of characters on each line is also reversed. If
no file is specified, rev
reads from standard input.
|
rexecd | rexecd command-line TCP/IP command. Server for the rexec
routine, providing remote execution facilities with authentication
based on usernames and passwords. rexecd is started by inetd
and must have an entry in inetd's configuration file,
/etc/inetd.conf. When rexecd receives a service request,
the following protocol is initiated:
The server reads characters from the socket up to a null byte. The
resulting string is interpreted as an ASCII number, base 10. If the number received in step 1 is nonzero, it is interpreted as the
port number of a secondary stream to be used for stderr. A second
connection is then created to the specified port on the client's
machine. A null-terminated username of at most 16 characters is retrieved on
the initial socket. A null-terminated, unencrypted password of at most 16 characters
is retrieved on the initial socket. A null-terminated command to be passed to a shell is retrieved on the
initial socket. The length of the command is limited by the upper bound
on the size of the system's argument list. rexecd then validates the user, as is done at login time and, if
the authentication was successful, changes to the user's home
directory and establishes the user and group protections of the user. A null byte is returned on the connection associated with stderr,
and the command line is passed to the normal login shell of the user.
The shell inherits the network connections established by
rexecd.
Diagnostics
- Username too long
Name is longer than 16 characters.
- Password too long
Password is longer than 16 characters.
- Command too long
Command passed is too long.
- Login incorrect
No password file entry for the username exists.
- Password incorrect
Wrong password was supplied.
- No remote directory
chdir to home directory failed.
- Try again
fork by server failed.
- <shellname>:...
fork by server failed.
User's login shell could not be started.
|
rlogin | rlogin rhost [options] Remote login. rlogin connects the terminal
on the current local host system to the remote host system rhost.
The remote terminal type is the same as your local terminal type. The
terminal or window size is also copied to the remote system if the server
supports it.
Options
- -8
Allow an 8-bit input data path at all times.
- -ec
Specify escape character c (default is ~).
- -d
Debugging mode.
- -k
Attempt to get tickets from remote host, requesting them in the realm
as determined by krb_realm-ofhost.
- -l username
Specify a different username for the remote login. Default is
the same as your local username.
- -x
Turns on DES encryption for all data passed via the rlogin
session.
- -E
Do not interpret any character as an escape character.
- -K
Suppress all Kerberos authentication.
- -L
Allow rlogin session to be run
without any output
postprocessing (i.e., run in litout mode).
|
rlogind | rlogind [options] TCP/IP command. Server for the rlogin
program, providing a remote login facility, with authentication based on
privileged port numbers from trusted hosts.
rlogind is invoked by inetd when a
remote login connection is requested and executes the following
protocol:
The server checks the client's source port. If the port is not in
the range 0-023, the server aborts the connection. The server checks the client's source address and requests the
corresponding hostname. If the hostname cannot be
determined, the dot-notation representation of the host address is used.
The login process propagates the client terminal's
baud rate and terminal type, as found in the environment variable,
TERM.
Options
- -a
Verify hostname.
- -l
Do not authenticate hosts via a nonroot .rhosts file.
- -n
Suppress keep-alive messages.
|
rm | rm [options] files Delete one or more files. To remove a file, you must have write
permission in the directory that contains the file, but you need not
have permission on the file itself. If you do not have write
permission on the file, you will be prompted (y or n) to override.
Options
- -d, --directory
Remove directories, even if they are not empty. Available only to
a privileged user.
- -f, --force
Remove write-protected files without prompting.
- --help
Print a help message and then exit.
- -i, --interactive
Prompt for y (remove the file) or
n (do not remove the file).
- -r, -R, --recursive
If file is a directory,
remove the entire directory and all its contents, including subdirectories. Be forewarned: use of this option can be dangerous.
- -v, --verbose
Turn on verbose mode. (rm prints the name of each file before
removing it.)
- --version
Print version information and then exit.
- --
Mark the end of options. Use this when you need to supply a filename
beginning with -.
|
rmail | rmail user... TCP/IP command. Handle remote mail received via
uucp, collapsing From lines
in the form generated by mail into a single line of the form
return-path!sender and passing the processed mail onto
sendmail. rmail is explicitly designed for use with
uucp and sendmail.
|
rmdir | rmdir [options] directories Delete the named directories (not the contents).
directories are deleted from the parent directory
and must be empty (if not, rm -r can be used instead).
See also mkdir.
Options
- --help
Print a help message and then exit.
- --ignore-fail-on-non-empty
Ignore failure to remove directories that are not empty.
- -p, --parents
Remove directories and any intervening parent directories
that become empty as a result; useful for removing subdirectory trees.
- --verbose
Turn on verbose mode; print message for each directory as it is processed.
- --version
Print version information and then exit.
|
rmmod | rmmod [option] modules System administration command.
Unload a module or list of modules from the kernel. This command
is successful only if the specified modules are not in use and no
other modules are dependent on them.
Option
- -r
Recursively remove stacked modules (all modules that use the
specified module).
|
rootflags | rootflags [option] image [flags [offset]] System administration command. Sets flags for a
kernel image. If no arguments are specified,
print flags for the kernel image.
flags is a 2-byte integer located at offset 498
in a kernel image. Currently the only effect of
flags is to mount the root filesystem in
read-only mode if flags is non-zero. You may
change flags by specifying the kernel
image to change, the new
flags, and the byte-offset at which to place the
new information (the default is 498). Note that rdev -R is a synonym for rootflags. If LILO is used, rootflags is not needed.
flags can be set from the LILO prompt during a
boot.
Option
- -o offset
Same as specifying an offset as an argument.
|
route | route [option] [command] TCP/IP command. Manually manipulate the routing tables normally
maintained by routed. route accepts two commands: add, to add a route, and del, to delete a route. The two commands have
the following syntax:
add [-net | -host] address [gw gateway]
[netmask mask] [mss tcp-mss] [dev device]
del address
address is treated as a plain route unless
-net is specified or
address is found in
/etc/networks. -host can be used to specify that
address is a plain route whether or not it is
found in /etc/networks. The keyword
default means to use this route for all requests
if no other route is known. You can specify the
gateway through which to route packets headed for
that address, its netmask, TCP
mss, and the device with
which to associate the route. Only a privileged user may modify the
routing tables.
If no command is specified, route
prints the routing tables.
Option
- -n
Show numerical addresses; do not look up hostnames. (Useful if DNS is not functioning properly.)
|
routed | routed [options] [logfile] TCP/IP command. Network routing daemon.
routed is invoked by a privileged user at
boot time to manage the Internet routing tables. The routing daemon
uses a variant of the Xerox NS Routing Information Protocol in
maintaining up-to-date kernel routing-table entries. When routed is
started, it uses the SIOCGIFCONF ioctl call to find those directly
connected interfaces configured into the system and marked up.
routed transmits a REQUEST packet on each interface, then
enters a loop, listening for REQUEST and RESPONSE packets
from other hosts. When a REQUEST packet is received, routed
formulates a reply based on the information maintained in its internal
tables. The generated RESPONSE packet contains a list of known
routes. Any RESPONSE packets received are used to update the
routing tables as appropriate.
When an update is applied, routed records the change in
its internal tables, updates the kernel routing table, and generates
a RESPONSE packet reflecting these changes to all directly connected
hosts and networks.
Options
- -d
Debugging mode. Log additional information to the logfile.
- -g
Offer a route to the default destination.
- -q
Opposite of -s option.
- -s
Force routed to supply routing information, whether it is acting
as an internetwork router or not.
- -t
Stop routed from going into background and releasing itself from
the controlling terminal, so that interrupts from the keyboard will kill
the process.
|
rpcgen | rpcgen [options] file Parse file, which should be written in the RPC language,
and produce a program written in C that implements the RPC code.
Place header code generated from file.x in file.h,
XDR routines in file_xdr.c, server code in file_svc.c,
and client code in file_clnt.c.
Lines preceded by % are not parsed. By default, rpcgen
produces SunOS 4.1-compatible code.
- -a
Produce all files (client and server).
- -5
Produce SVR4-compatible code.
- -c
Create XDR routines. Cannot be used with other options.
- -C
Produce ANSI C code (default).
- -Dname[=value]
Define the symbol name, and set it equal to value or 1.
- -h
Produce a header file. With -T, make the file support
RPC dispatch tables. Cannot be used with other options.
- -I
Produce an inetd-compatible server.
- -K secs
Specify amount of time that the server should wait after replying to
a request and before exiting. Default is 120. A secs of -1
prevents the program from ever exiting.
- -l
Produce client code.
Cannot be used with other options.
- -m
Produce server code only, suppressing creation of a "main" routine.
Cannot be used with other options.
- -N
New style. Allow multiple arguments for procedures. Not
necessarily backward compatible.
- -o [file]
Print output to file or standard output.
- -Ss
Create skeleton server code only.
- -t
Create RPC dispatch table. Cannot be used with other options.
- -T
Include support for RPC dispatch tables.
|
rpcinfo | rpcinfo [options] [host] [program] [version] NFS/NIS command. Report RPC information.
program can be either a name or a number.
If a version is specified, rpcinfo attempts to call that
version of the specified program. Otherwise, it attempts to find
all the registered version numbers for the specified program by
calling Version 0, and it attempts to call each registered version.
Options
- -b program version
Make an RPC broadcast to the specified program and
version, using UDP, and report all hosts that respond.
- -d program version
Delete the specified version of program's registration.
Can be executed only by the user who added the registration
or a privileged user.
- -n portnum
Use portnum as the port number for the -t and -u options,
instead of the port number given by the portmapper.
- -p [host]
Probe the portmapper on host and print a list of all registered RPC
programs. If host is not specified, it defaults to the value returned
by hostname.
- -t host program [version]
Make an RPC call to program on the specified host,
using TCP, and report whether a response was received.
- -u host program [version]
Make an RPC call to program on the specified host,
using UDP, and report whether a response was received.
Examples
To show all of the RPC services registered on the local machine,
use:
$ rpcinfo -p
To show all of the RPC services registered on the machine named
klaxon, use:
$ rpcinfo -p klaxon
To show all machines on the local net that are running the Network
Information Service (NIS), use:
$ rpcinfo -b ypserv version | uniq
where version is the current NIS version obtained from the results of
the -p switch earlier in this list.
|
rpm | rpm [options] The Red Hat Package Manager. A freely available packaging system for
software distribution and installation. RPM packages are built, installed, and
queried with the rpm command. For detailed
information on rpm, see Chapter 5, "Red Hat and Debian Package Managers".
|
rsh | rsh [options] host [command] Execute command on remote host, or, if no command is
specified, begin an interactive shell on the remote host using
rlogin.
Options
- -d
Enable socket debugging.
- -k
Cause rsh to obtain tickets for the remote host in
realm instead of the remote host's realm as determined by
krb_realmofhost(3).
- -l username
Attempt to log in as username. By default, the name of the
user executing rsh is used.
- -n
Redirects the input to rsh from the special device
/dev/null. (This should be done when backgrounding rsh
from a shell prompt, to direct the input away from the terminal.)
- -x
Turns on DES encryption for all data exchange.
- -K
Suppress Kerberos authentication.
|
rshd | rshd [options] TCP/IP command. Remote shell server for programs
such as rcmd and rcp, which need to execute a
noninteractive shell on remote machines. rshd is started by inetd
and must have an entry in inetd's configuration file,
/etc/inetd.conf.
All options are exactly the same as those in rlogind, except for
-L, which is unique to rshd.
Option
- -L
Log all successful connections and failed attempts via syslogd.
|
rstat | rstat host TCP/IP command. Summarize host's system status: the
current time, uptime,
and load averages -- the average number of jobs in the run queue.
Queries the remote host's rstat_svc daemon.
|
run-parts | run-parts [options] [directory] System administration command.
Run, in lexical order, all scripts found in directory. Exclude
scripts whose filenames include nonalphanumeric characters (besides
underscores and hyphens).
Options
- --
Interpret all subsequent arguments as filenames, not options.
- --test
Print information listing which scripts would be run, but suppress
actual execution of them.
- --umask=umask
Specify umask. The default is 022.
|
runlevel | runlevel System administration command.
Display the previous and current system runlevels.
|
ruptime | ruptime [options] TCP/IP command. Provide information on how long each machine on the local
network has been up and which users are logged in to each.
If a machine has not reported in for 11 minutes, assume it
is down. The listing is sorted by hostname.
Options
- -a
Include users who have been idle for more than one hour.
- -l
Sort machines by load average.
- -r
Reverse the normal sort order.
- -t
Sort machines by uptime.
- -u
Sort machines by the number of users logged in.
|
rusers | rusers [options] [host] TCP/IP command. List the users logged on to host, or to
all local machines, in who format (hostname, usernames).
Options
- -a
Include machines with no users logged in.
- -l
Include more information: tty, date, time, idle time,
remote host.
|
rwall | rwall host [file] TCP/IP command. Print a message to all users logged on to host. If
file is specified, read the message from it;
otherwise, read from standard input.
|
rwho | rwho [option] Report who is logged on for all machines on the local network
(similar to who).
Option
- -a
List users even if they've been idle for more than one hour.
|
rwhod | rwhod TCP/IP command. System status server that maintains the
database used by the rwho and ruptime programs. Its operation
is predicated on the ability to broadcast messages on a network. As
a producer of information, rwhod periodically queries the state of the
system and constructs status messages, which are broadcast on a
network. As a consumer of information, it listens for other rwhod
servers' status messages, validates them, then records them in a
collection of files located in the directory /var/spool/rwho. Messages
received by the rwhod server are discarded unless they
originated at an rwhod server's port. Status messages are generated
approximately once every 3 minutes.
|
script | script [option] [file] Fork the current shell and make a typescript of a terminal session.
The typescript is written to file. If no file is given,
the typescript is saved in the file typescript. The script ends
when the forked shell exits, usually with Ctrl-D or exit.
Option
- -a
Append to file or typescript instead of overwriting the
previous contents.
|
sed | sed [options] [command] [files] Stream editor -- edit one or more files without user interaction.
See Chapter 12, "The sed Editor", for more information.
|
sendmail | sendmail [flags] [address...] System administration command.
sendmail is a mail transfer agent (MTA) or, more simply, a mail router.
It accepts mail from a user's mail program, interprets the mail
address, rewrites the address into the proper form for the
delivery program, and routes the mail to the correct delivery
program.
Command-line flags
- -bx
Set operation mode to x. Operation modes are:
- a
Run in ARPAnet mode.
- d
Run as a daemon.
- i
Initialize the alias database.
- m
Deliver mail (default).
- p
Print the mail queue.
- s
Speak SMTP on input side.
- t
Run in test mode.
- v
Verify addresses; do not collect or deliver.
- -C file
Use configuration file file.
- -d level
Set debugging level.
- -F name
Set full name of user to name.
- -f name
Sender's name is name.
- -h cnt
Set hop count (number of times message has been processed by sendmail)
to cnt.
- -n
Do not alias or forward.
- -o x value
Set option x to value value. Options are described below.
- -p protocol
Receive messages via the protocol protocol.
- -q [time]
Process queued messages immediately, or at intervals indicated by
time (for example, -q30m for every half hour).
- -r name
Obsolete form of -f.
- -t
Read head for To:, Cc:, and Bcc: lines, and send
to everyone on those lists.
- -v
Verbose.
- -X file
Log all traffic to file. Not to be used for normal logging.
Configuration options
The following options can be set with the -o flag on the
command line or the O line in the configuration file:
- 7
Format all incoming messages in 7 bits.
- amin
If the D option is set, wait min minutes for the aliases file
to be rebuilt before returning an alias database
out-of-date warning.
- Afile
Use alternate alias file.
- bminblocks[/maxsize]
Require at least minblocks to be free, and
optionally set the maximum message size to maxsize.
If maxsize is omitted, the slash is optional.
- Bchar
Set unquoted space replacement character.
- c
On mailers that are considered "expensive" to connect to, don't
initiate immediate connection.
- Cnum
Checkpoint the queue when mailing to multiple
recipients. sendmail will rewrite the list of
recipients after each group of num
recipients has been processed.
- dx
Set the delivery mode to x. Delivery modes are d for
deferred delivery, i for
interactive (synchronous) delivery, b for background (asynchronous)
delivery, and q for queue only -- i.e., deliver
the next time the queue is run.
- D
Try to automatically rebuild the alias database if necessary.
- ex
Set error processing to mode x. Valid modes are m to mail
back the error message, w to write back the error message, p to
print the errors on the terminal (default), q to throw away error
messages, and e to do special processing for the BerkNet.
- Etext
Set error message header. text is either text
to add to an error message or the name of a file. A filename must include its full path and begin
with a /.
- f
Save Unix-style From lines at the front of messages.
- Fmode
Set default file permissions for temporary files. If
this option is missing, default permissions are 0644.
- G
Compare local mail names to the GECOS section in the password file.
- g n
Default group ID to use when calling mailers.
- Hfile
SMTP help file.
- h num
Allow a maximum of num hops per message.
- i
Do not take dots on a line by themselves as a message terminator.
- I arg
Use DNS lookups and tune them. Queue messages on connection refused.
The arg arguments are identical to resolver flags without
the RES_ prefix. Each flag can be preceded by a plus or minus to
enable or disable the corresponding name server option.
There must be
a whitespace between the I and the first flag.
- j
Use MIME format for error messages.
- Jpath
Set an alternative .forward search path.
- knum
Specify size of the connection cache.
- Ktime
Time out connections after time.
- l
Do not ignore Errors-To header.
- Ln
Specify log level.
- m
Send to me (the sender) also if I am in an alias expansion.
- MXvalue
Define a macro's value in command line. Assign value to macro
X.
- n
When running newaliases, validate the right side of aliases.
- o
If set, this message may have old-style headers. If not set, this
message is guaranteed to have new-style headers (i.e., commas
instead of spaces between addresses).
- pwhat,what,...
Tune how private you want the SMTP daemon. The what arguments
should be separated from one another by commas. The what
arguments may be any of the following:
- public
Make SMTP fully public (default).
- needmailhelo
Require site to send HELO or ELHO before sending mail.
- needexpnhelo
Require site to send HELO or ELHO before answering an address
expansion request.
- needvrfyhelo
Like preceding argument but for verification requests.
- noexpn
Deny all expansion requests.
- novrfy
Deny all verification requests.
- authwarnings
Insert special headers in mail messages advising recipients that
the message may not be authentic.
- goaway
Set all of the previous arguments (except public).
- restrictmailq
Allow only users of the same group as the owner of the queue directory
to examine the mail queue.
- restrictqrun
Limit queue processing to root and the owner of the queue directory.
- Puser
Send copies of all failed mail to user (usually postmaster).
- qfact
Multiplier (factor) for high-load queuing.
- Qqueuedir
Select the directory in which to queue messages.
- R
Don't prune route addresses.
- Sfile
Save statistics in the named file.
- s
Always instantiate the queue file, even under circumstances in which
it is not strictly necessary.
- Ttime
Set the timeout on undelivered messages in the queue to the specified
time.
- tstz, dtz
Set name of the time zone.
- Udatabase
Consult the user database database for forwarding information.
- uN
Set default user ID for mailers.
- v
Run in verbose mode.
- Vhost
Fall-back MX host. host should be the fully qualified
domain name of the fallback host.
- w
Use a record for an ambiguous MX.
- xload
Queues messages when load level is higher than load.
- Xload
Refuse SMTP connections when load is higher than load.
- yfactor
Penalize large recipient lists by factor.
- Y
Deliver each job that is run from the queue in a separate process. This helps limit the size of running processes on systems with very
low amounts of memory.
- zfactor
Multiplier for priority increments. This determines how much weight
to give to a message's precedence header. sendmail's default is 1800.
- Zinc
Increment priority of items remaining in queue by inc after each
job is processed. sendmail uses 90,000 by default.
sendmail support files
- /usr/lib/sendmail
Binary of sendmail.
- /usr/bin/newaliases
Link to /usr/lib/sendmail; causes the alias database to
be rebuilt.
- /usr/bin/mailq
Prints a listing of the mail queue.
- /etc/sendmail.cf
Configuration file, in text form.
- /etc/sendmail.hf
SMTP help file.
- /usr/lib/sendmail.st
Statistics file. Doesn't need to be present.
- /etc/aliases
Alias file, in text form.
- /etc/aliases.{pag,dir}
Alias file in dbm format.
- /var/spool/mqueue
Directory in which the mail queue and temporary files reside.
- /var/spool/mqueue/qf
Control (queue) files for messages.
- /var/spool/mqueue/df
Data files.
- /var/spool/mqueue/lf
Lockfiles.
- /var/spool/mqueue/tf
Temporary versions of af files, used during queue-file rebuild.
- /var/spool/mqueue/nf
Used when creating a unique ID.
- /var/spool/mqueue/xf
Transcript of current session.
|
setfdprm | setfdprm [options] device [name] Load disk parameters used when autoconfiguring floppy devices.
Options
- -c device
Clear parameters of device.
- -n device
Disable format-detection messages for device.
- -p device [name | parameter]
Permanently reset parameters for device. You can use
name to specify a configuration, or you can specify
individual parameters. The parameters
that can be specified are dev,
size, sect,
heads,
tracks,
stretch,
gap,
rate,
spec1, or
fmt_gap. Consult
/etc/fdprm for the original values.
- -y device
Enable format-detection messages for device.
|
setsid |
setsid command [arguments] System administration command. Execute the named command and optional
command arguments in a new session.
|
sh | sh [options] [file [arguments]] The standard Unix shell, a command interpreter into which all
other commands are entered. On Linux, this is just another name
for the bash shell. For more information, see Chapter 7, "bash: The Bourne-Again Shell",
.
|
shar | shar [options] files shar -S [options]
Create shell archives (or shar files) that are in text format
and can be mailed.
These files may be unpacked later by executing them with
/bin/sh. Other commands may be required on the recipient's
system, such as compress, gzip, and uudecode.
The resulting archive is sent to
standard output, unless the -o option is given.
Options
- -a, --net-headers
Allows automatic generation of headers. The -n option is required if the -a option is used.
- -b bits, --bits-per-code=bits
Use -b bits as a parameter to compress
(when doing compression). Default
value is 12. The -b option
automatically turns on -Z.
- -c, --cut-mark
Start the shar file with a line that says "Cut here."
- -d delimiter, --here-delimiter=delimiter
Use delimiter for the files in the shar instead of SHAR_EOF.
- -f, --basename
Causes only simple filenames to be used when restoring, which is
useful when building a shar from several directories or
another directory. (If a directory
name is passed to shar, the substructure of
that directory will be restored whether or not -f is used.)
- -g level, --level-for-gzip=level
Use -level as a parameter to gzip (when
doing compression). Default is 9. The -g option turns
on the -z option by default.
- --help
Print a help summary on standard output, then exit.
- -l nn, --whole-size-limit=nn
Limit the output file size to nn kilobytes but don't
split input files. Requires use of -o.
- -m, --no-timestamp
Don't generate touch commands to restore the
file modification dates when unpacking files from the archive.
- -n name, --archive-name=name
Name of archive to be included in the header of the
shar files. Required if the -a option is used.
- --no-i18n
Do not produce internationalized shell archives;
use default English messages. By default, shar
produces archives that will try to output messages
in the unpacker's preferred language (as determined by
LANG/LC_MESSAGES).
- -o prefix, --output-prefix=prefix
Save the archive to files prefix.01 through
prefix.nn (instead of sending it to standard output).
This option must be used when
either -l or -L is used.
- -p, --intermix-type
Allow positional parameter options. The options
-B, -T, -z, and -Z may be
embedded, and files to the right of the option will be
processed in the specified mode.
- --print-text-domain-dir
Print the directory shar looks in to find messages
files for different languages, then immediately exit.
- -q, --quiet, --silent
Turn off verbose mode.
- -s who@where, --submitter=who@where
Supply submitter name and address, instead of allowing shar to determine
it automatically.
- --version
Print the version number of the program on standard
output, then exit.
- -w, --no-character-count
Do not check each file with wc -c after unpacking.
The default is to check.
- -x, --no-check-existing
Overwrite existing files without checking. Default
is to check and not overwrite existing files. If -c is passed as a parameter to the
script when unpacking (sh archive -c),
existing files will be overwritten
unconditionally. See also -X.
- -z, --gzip
gzip and uuencode all files prior to packing. Must be unpacked with uudecode and gunzip (or zcat).
- -B, --uuencode
Treat all files as binary; use uuencode prior to
packing. This increases the size of the archive,
and it must be unpacked with uudecode.
- -D, --no-md5-digest
Do not use md5sum digest to verify the unpacked
files. The default is to check.
- -F, --force-prefix
Force the prefix character to
be prepended to every line even if not required.
May slightly increase the size of the
archive, especially if -B or -Z is used.
- -L nn, --split-size-limit=nn
Limit output file size to nn kilobytes and split files
if necessary. The archive parts created with this
option must be unpacked in correct order.
Requires use of
-o.
- -M, --mixed-uuencode
Pack files in mixed mode (the default).
Distinguishes files as either text or binary;
binaries are uuencoded prior to packing.
- -P, --no-piping
Use temporary files instead of pipes in the shar file.
- -Q, --quiet-unshar
Disable verbose mode.
- -S, --stdin-file-list
Read list of files to be packed from standard
input rather than from the command line. Input must be in a form similar to that generated by the
find command, with one filename per line.
- -T, --text-files
Treat all files as text.
- -V, --vanilla-operation
Produce shars that rely only upon the
existence of sed and echo in the
unsharing environment.
- -X, --query-user
Prompt user to ask if files should be overwritten
when unpacking.
- -Z, --compress
Compress and uuencode all files prior to packing.
|
showmount | showmount [options] [host] NFS/NIS command.
Show information about an NFS server.
This information is
maintained by the mountd server on host. The default value
for host is the value returned by hostname. With no options,
show the clients that have mounted directories from the host.
showmount is usually found in /usr/sbin, which is
not in the default search path.
Options
- -a, --all
Print all remote mounts in the format:
hostname:directory
where hostname is the name of the client and directory is
the root of the filesystem that has been mounted.
- -d, --directories
List directories that have been remotely mounted by clients.
- -e, --exports
Print the list of exported filesystems.
- -h, --help
Provide a short help summary.
- --no-headers
Do not print headers.
- -v, --version
Report the current version number of the program.
|
shutdown | shutdown [options] when [message] System administration command.
Terminate all processing. when may be a specific time (in
hh:mm format), a number of minutes to wait (in
+m format), or now.
A broadcast message notifies all users to log
off the system. Processes are signaled with SIGTERM, to
allow them to exit gracefully. /etc/init is called to perform
the actual shutdown, which consists of placing the system in runlevel 1.
Only privileged users can execute the shutdown command.
Broadcast messages, default or defined, are displayed at regular
intervals during the grace period; the closer the shutdown time, the
more frequent the message.
Options
- -c
Cancel a shutdown that is in progress.
- -f
Reboot fast, by suppressing the normal call to fsck when rebooting.
- -h
Halt the system when shutdown is complete.
- -k
Print the warning message, but suppress actual shutdown.
- -n
Perform shutdown without a call to init.
- -r
Reboot the system when shutdown is complete.
- -t sec
Ensure a sec-second delay between killing processes and
changing the runlevel.
|
size | size [options] [objfile...] Print the number of bytes of each section of objfile
and its total size.
If objfile is not specified, a.out is used.
Options
- -d
Display the size in decimal and hexadecimal.
- --format format
Imitate the size command from either System V (--format
sysv) or BSD (--format berkeley).
- -o
Display the size in octal and hexadecimal.
- --radix num
Specify how to display the size: in hexadecimal and decimal
(if num is 10 or 16) or hexadecimal and
octal (if num is 8).
- -x
Display the size in hexadecimal and decimal.
- -A
Imitate System V's size command.
- -B
Imitate BSD's size command.
|
slattach | slattach [options] [tty] TCP/IP command. Attach serial lines as network interfaces,
thereby preparing them for use as point-to-point connections.
Only a privileged user may attach or detach a network interface.
Options
- -c command
Run command when the connection is severed.
- -d
Debugging mode.
- -e
Exit immediately after initializing the line.
- -h
Exit when the connection is severed.
- -l
Create UUCP-style lockfile in /var/spool/uucp.
- -L
Enable 3-wire operation.
- -m
Suppress initialization of the line to 8 bits raw mode.
- -n
Similar to mesg -n.
- -p protocol
Specify protocol, which may be slip, adaptive,
ppp, or kiss.
- -q
Quiet mode; suppress messages.
- -s speed
Specify line speed.
|
sleep | sleep amount[units] Wait a specified amount of time before
executing another command. The default for units is seconds.
Time |
Units |
s |
seconds |
m |
minutes |
h |
hours |
d |
days |
|
sort | sort [options] [files] Sort the lines of the named files. Compare specified fields for
each pair of lines, or, if no fields are specified, compare them
by byte, in machine collating sequence.
See also uniq, comm, and join.
Options
- -b
Ignore leading spaces and tabs.
- -c
Check whether files are already sorted, and, if so, produce no
output.
- -d
Sort in dictionary order.
- -f
Fold -- ignore uppercase/lowercase differences.
- --help
Print a help message and then exit.
- -i
Ignore nonprinting characters (those outside ASCII range 040-176).
- -m
Merge (i.e., sort as a group) input files.
- -n
Sort in arithmetic order.
- -ofile
Put output in file.
- -r
Reverse the order of the sort.
- -tc
Separate fields with c (default is a tab).
- -u
Identical lines in input file appear only one (unique) time in
output.
- -zrecsz
Provide recsz bytes for any one line in
the file. This option prevents abnormal termination
of sort in certain
cases.
- +n [-m]
Skip n fields before sorting, and sort up to field position
m. If m is missing, sort to end of line.
Positions take the form a.b, which means
character b of field a. If .b is missing,
sort at the first character of the field.
- -k n[,m]
Similar to +. Skip n-1 fields and stop at m-1 fields (i.e., start
sorting at the nth field, where the fields are numbered beginning with
1).
- --version
Print version information and then exit.
- -M
Attempt to treat the first three characters as a month designation
(JAN, FEB, etc.). In comparisons, treat JAN < FEB and any valid month as less than an invalid name for a month.
- -T tempdir
Directory pathname to be used for temporary files.
Examples
List files by decreasing number of lines:
wc -l * | sort -r
Alphabetize a list of words, remove duplicates, and print the frequency
of each word:
sort -fd wordlist | uniq -c
Sort the password file numerically by the third field (user ID):
sort +2n -t: /etc/passwd
|
split | split [option] [infile] [outfile] Split infile into equal-sized segments.
infile remains unchanged, and the results are written to
outfileaa,
outfileab, and so on.
(default is xaa,
xab, etc.). If infile
is - (or missing), standard input is
read. See also csplit.
Options
- -n, -l n, --lines=n
Split infile into n-line segments
(default is 1000).
- -b n[bkm], --bytes=n[bkm]
Split infile into n-byte segments. Alternate blocksizes may be specified:
- b
512 bytes
- k
1 kilobyte
- m
1 megabyte
- -C bytes[bkm], --line-bytes=bytes[bkm]
Put a maximum of bytes into file; insist on adding
complete lines.
- --help
Print a help message and then exit.
- --verbose
Print a message for each output file.
- --version
Print version information and then exit.
- -
Take input from the standard input.
Examples
Break bigfile into 1000-line segments:
split bigfile
Join four files, then split them into 10-line files named
new.aa, new.ab, and so on. Note that without the -, new.
would be treated as a nonexistent input file:
cat list[1-4] | split -10 - new.
|
stat | stat filename [filenames . . . ] Print out the contents of an inode as they appear to the
stat system call in a human-readable format.
The error messages "Can't stat file" or "Can't lstat file"
usually mean the file doesn't exist.
"Can't readlink file" generally indicates that something
is wrong with a symbolic link.
Output
Sample output from the command:
stat /
File: "/"
Size: 1024 Filetype: Directory
Mode: (0755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ system)
Device: 3,3 Inode: 2 Links: 21
Access: Tue Apr 11 04:02:01 2000(00000.11:47:35)
Modify: Wed Nov 17 11:46:38 1999(00146.03:02:58)
Change: Wed Nov 17 11:46:38 1999(00146.03:02:58)
|
strace |
strace [options] command [arguments] Trace the system calls and signals for command
and arguments. strace shows you how data is passed between the
program and the system kernel. With no options, strace prints a line to stderr for each system call. It shows the call
name, arguments given, the return value, and any error messages
generated. A signal is printed with both its signal symbol and a
descriptive string.
Options
- -a n
Align the return values in column n.
- -c
Count all calls and signals and create a summary report when the
program has ended.
- -d
Debug mode. Print debugging information for strace on stderr.
- -e keyword[=[!]values
Pass an expression to strace to
limit the types of calls or signals that are traced or change how they are
displayed. The values for these expressions can be given as a comma-separated list. Preceding the list with an exclamation mark (!) negates the list. The special
values of all and
none are valid, as are the
values listed with the following keywords.
- abbrev=names
Abbreviate output from large structures for system calls
listed in names.
- read=descriptors
Print all data read from the given file descriptors.
- signal=symbols
Trace the listed signal symbols (for example,
signal=SIGIO,SIGHUP).
- trace=values
Trace the listed values. values may be a
list of system call names or one of the following sets of system
calls:
file |
Calls that take a filename as an argument |
ipc |
Interprocess communication |
network |
Network-related |
process |
Process management |
signal |
Signal-related |
- verbose=names
Unabbreviate structures for the given system call
names. Default is none.
- write=descriptors
Print all data written to the given file
descriptors.
- -f
Trace forked processes.
- -ff
Write system calls for forked processes to separate files named
filename.pid when using the -o option.
- -h
Print help and exit.
- -i
Print instruction pointer with each system call.
- -o filename
Write output to filename instead of stderr. If filename starts
with the pipe symbol |, treat the rest of the name as a command to
which output should be piped.
- -O n
Override strace's built-in timing
estimates, and just subtract n microseconds from the
timing of each system call to adjust for the time it takes to measure thestentry>
call.
- -p pid
Attach to the given process ID and begin tracking. strace can track more than one process if more than
one option -p is given. Type Ctrl-c
to end the trace.
- -q
Quiet mode. Suppress attach and detach messages from strace.
- -r
Relative timestamp. Print time in microseconds between system
calls.
- -s n
Print only the first n characters of a string.
Default value is 32.
- -S value
Sort output of -c option by
the given value. value may be
calls, name, time, or
nothing. By default it is sorted by
time.
- -T
Print time spent in each system call.
- -t
Print time of day on each line of output.
- -tt
Print time of day with microseconds on each line of output.
- -ttt
Print timestamp on each line as number of seconds since the Epoch.
- -u username
Run command as username. Needed when tracing
setuid and setgid programs.
- -V
Print version and exit.
- -v
Verbose. Do not abbreviate structure information.
- -x
Print all non-ASCII strings in hexadecimal.
- -xx
Print all strings in hexadecimal.
|
strfile | strfile [options] input_file [output_file] unstr [-c delimiter] input_file[.ext] [output_file] strfile creates a random-access file
for storing strings. The input file should be a file
containing groups of lines separated
by a line containing a single percent sign (or other
specified delimiter character). strfile
creates an output file that contains a header structure and a
table of file offsets for each group of lines, allowing
random access of the strings.
The output file, if not specified on the command line, is
named sourcefile.dat.
unstr undoes the work of
strfile, printing out
the strings contained in the input file in the order
that they are listed in the header file data.
If no output file is specified,
unstr prints to standard output;
otherwise, it prints to the file specified.
unstr can also globally change the delimiter
character in a strings file.
Options
Of the following options, only -c can be used with unstr.
All other options apply to strfile alone.
- -c delimiter
Change the delimiting character from the percent
sign to delimiter. Valid for both
strfile and unstr.
- -i
Ignore case when ordering the strings.
- -o
Order the strings alphabetically.
- -r
Randomize access to the strings.
- -s
Run silently; don't give a summary message when finished.
- -x
Set the STR_ROTATED bit in the header str_flags field.
|
strings | strings [options] files Search each file specified and print any printable
character strings found that are at least four characters long and
followed by an unprintable character.
Options
- -, -a, --all
Scan entire object files; default is to scan only the initialized
and loaded sections for object files.
- -f, --print-file-name
Print the name of the file before each string.
- -min-len, -n min-len, --bytes=min-len
Print only strings that are at least min-len characters.
- -t base, --radix=base
Print the offset within the file before each string, in the format specified
by base:
- d
Decimal
- o
Octal
- x
Hexadecimal
- --target=format
Specify an alternative object code format to the system default.
- -o
Same as -t o.
- --help
Print help message and then exit.
- -v, --version
Print version information and then exit.
|
strip | strip [options] files Remove symbols from object files,
thereby reducing file sizes and freeing disk space.
Options
- -F format, --target=format
Expect the input file to be in the format format.
- -O format, --output-target=format
Write output file in format.
- -R section, --remove-section=section
Delete section.
- -s, --strip-all
Strip all symbols.
- -S, -g,--strip-debug
Strip debugging symbols.
- -x, --discard-all
Strip nonglobal symbols.
- -X, --discard-locals
Strip local symbols that were generated by the compiler.
- -v, --verbose
Verbose mode.
|
stty | stty [options] [modes] Set terminal I/O options for the current
standard input device. Without options,
stty reports the terminal settings
that differ from those set by running stty sane, where a
^ indicates the Ctrl key
and ^` indicates a null value.
Most modes can be negated
using an optional - (shown in brackets).
The corresponding description is also shown in brackets.
Some arguments use non-POSIX extensions; these are marked with a *.
Options
- -a, --all
Report all option settings.
- -g
Report settings in hex.
Control modes
- n
Set terminal baud rate to n (e.g., 2400).
- [-]clocal
[Enable] disable modem control.
- [-]cread
[Disable] enable the receiver.
- csbits
Set character size to bits, which must be 5, 6, 7, or 8.
- [-]cstopb
[1] 2 stop bits per character.
- [-]hup
[Do not] hang up connection on last close.
- [-]hupcl
Same as previous.
- ispeed n
Set terminal input baud rate to n.
- ospeed n
Set terminal output baud rate to n.
- [-]parenb
[Disable] enable parity generation and detection.
- [-]parodd
Use [even] odd parity.
- [-]crtscts*
[Disable]enable RTS/CTS handshaking.
Flow control modes
The following flow control modes are available by combining
the ortsfl, ctsflow, and rtsflow flags:
Flag Settings |
Flow Control Mode |
ortsfl rtsflow ctsflow |
Enable unidirectional flow control. |
ortsfl rtsflow -ctsflow |
Assert RTS when ready to send. |
ortsfl -rtsflow ctsflow |
No effect. |
ortsfl -rtsflow -ctsflow |
Enable bidirectional flow control. |
-ortsfl rtsflow ctsflow |
Enable bidirectional flow control. |
-ortsfl rtsflow -ctsflow |
No effect. |
-ortsfl -rtsflow ctsflow |
Stop transmission when CTS drops. |
-ortsfl -rtsflow -ctsflow |
Disable hardware flow control. |
Input modes
- [-]brkint
[Do not] signal INTR on break.
- [-]icrnl
[Do not] map CR to NL on input.
- [-]ignbrk
[Do not] ignore break on input.
- [-]igncr
[Do not] ignore CR on input.
- [-]ignpar
[Do not] ignore parity errors.
- [-]inlcr
[Do not] map NL to CR on input.
- [-]inpck
[Disable] enable input parity checking.
- [-]istrip
[Do not] strip input characters to 7 bits.
- [-]iuclc*
[Do not] map uppercase to lowercase on input.
- [-]ixany*
Allow [XON] any character to restart output.
- [-]ixoff [-]tandem
[Do not] send START/STOP characters when queue is nearly
empty/full.
- [-]ixon
[Disable] enable START/STOP output control.
- [-]parmrk
[Do not] mark parity errors.
- [-]imaxbel*
When input buffer is too full to accept a new character, [flush the
input buffer] beep without flushing the input buffer.
Output modes
- bsn
Select style of delay for backspaces (0 or 1).
- crn
Select style of delay for carriage returns (0-3).
- ffn
Select style of delay for formfeeds (0 or 1).
- nln
Select style of delay for linefeeds (0 or 1).
- tabn
Select style of delay for horizontal tabs (0-3).
- vtn
Select style of delay for vertical tabs (0 or 1).
- [-]ocrnl*
[Do not] map CR to NL on output.
- [-]ofdel*
Set fill character to [NULL] DEL.
- [-]ofill*
Delay output with [timing] fill characters.
- [-]olcuc*
[Do not] map lowercase to uppercase on output.
- [-]onlcr*
[Do not] map NL to CR-NL on output.
- [-]onlret*
On the terminal, NL performs [does not perform] the CR function.
- [-]onocr*
Do not [do] output CRs at column 0.
- [-]opost
[Do not] postprocess output.
Local modes
- [-]echo
[Do not] echo every character typed.
- [-]echoe, [-]crterase
[Do not] echo ERASE character as BS-space-BS string.
- [-]echok
[Do not] echo NL after KILL character.
- [-]echonl
[Do not] echo NL.
- [-]icanon
[Disable] enable canonical input (ERASE, KILL, WERASE,
and RPRINT processing).
- [-]iexten
[Disable] enable extended functions for input data.
- [-]isig
[Disable] enable checking of characters against INTR, SUSPEND, and
QUIT.
- [-]noflsh
[Enable] disable flush after INTR or QUIT.
- [-]tostop*
[Do not] send SIGTTOU
when background processes write to the
terminal.
- [-]xcase*
[Do not] change case on local output.
- [-]echoprt, [-]prterase*
When erasing characters, echo them backward, enclosed in \ and /.
- [-]echoctl. [-]ctlecho*
Do not echo control characters literally. Use hat notation
(e.g., ^Z).
- [-]echoke [-]crtkill*
Erase characters as specified by the echoprt and echoe settings
(default is echoctl and echok settings).
Control assignments
- ctrl-char c
Set control character to c.
ctrl-char is dsusp (flush input and then send stop), eof,
eol, eol2 (alternate end-of-line), erase, intr,
lnext (treat next character literally), kill,
rprnt (redraw line), quit, start, stop, susp,
swtch, or werase (erase previous word).
c can be a literal control character, a character in hat notation
(e.g., ^Z), in hex (must begin with 0x), in octal (must begin with 0),
or in decimal. Disable the control character with values of ^-
or undef.
- min n
Set the minimum number of characters that will satisfy a read
until the time value has expired when -icanon is set.
- time n
Set the number of tenths of a second before reads
time out if the min number of characters have not
been read when -icanon is set.
- line i
Set line discipline to i (1-126).
Combination modes
- cooked
Same as -raw.
- [-]evenp [-]parity
Same as [-]parenb and cs[8]7.
- [-]parity
Same as [-]parenb and cs[8]7.
- ek
Reset ERASE and KILL characters to Ctrl-h and Ctrl-u,
their defaults.
- [-]lcase
[Un] set xcase, iuclc, and olcuc.
- [-]LCASE
Same as [-]lcase.
- [-]nl
[Un] set icrnl and onlcr. -nl also unsets
inlcr, igncr, ocrnl, and onlret,
icrnl, onlcr.
- [-]oddp
Same as [-]parenb, [-]parodd, and
cs7[8].
- [-]raw
[Disable] enable raw input and output (no ERASE, KILL,
INTR, QUIT, EOT, SWITCH, or output
postprocessing).
- sane
Reset all modes to reasonable values.
- [-]tabs*
[Expand to spaces] preserve output tabs.
- [-]cbreak
Same as -icanon.
- [-]pass8
Same as -parenb -istrip cs8.
- [-]litout
Same as -parenb -istrip cs8.
- [-]decctlq*
Same as -ixany.
- crt
Same as echoe echoctl echoke.
- dec
Same as echoe echoctl echoke -ixany.
Additionally, set INTERRUPT to ^C, ERASE to DEL, and KILL to ^U.
Special settings
- ispeed speed
Specify input speed.
- ospeed speed
Specify output speed.
- rows rows*
Specify number of rows.
- cols columns, columns columns*
Specify number of columns.
- size*
Display current row and column settings.
- line discipline*
Specify line discipline.
- speed
Display terminal speed.
|
su | su [option] [user] [shell_args] Create a shell with the effective user-ID user.
If no user is specified, create a shell for a
privileged user (that is, become a superuser). Enter EOF to terminate.
You can run the shell with particular options by passing them
as shell_args (e.g., if the shell runs sh, you can specify
-c command to execute command via sh
or -r to create a restricted shell).
Options
- -, -l, --login
Go through the entire login sequence (i.e., change to
user's environment).
- -c command, --command=command
Execute command in the new shell and then exit immediately.
If command is more than one word, it should
be enclosed in quotes -- for example:
su -c 'find / -name \*.c -print' nobody
- -f, --fast
Start shell with -f option. In
csh and tcsh,
this suppresses the reading of the .cshrc file. In
bash, this suppresses filename
pattern expansion.
- -m, -p, --preserve-environment
Do not reset environment variables.
- -s shell, --shell=shell
Execute shell, not the shell specified in
/etc/passwd, unless shell
is restricted.
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
sum | sum [options] files Calculate and print a checksum and the number of (1KB)
blocks for file. Useful for verifying data transmission.
Options
- -r
The default setting. Use the BSD checksum algorithm.
- -s, --sysv
Use alternate checksum algorithm as used on System V.
The blocksize is 512 bytes.
- --help
Print a help message and then exit.
- --version
Print the version number and then exit.
|
swapdev | swapdev [option] [image [swapdevice [offset]]] System administration command.
If no arguments are given,
display usage information about the swap device.
If just the location of the kernel image is
specified, print the information found there. To change
that information, specify the new swapdevice. You
may also specify the offset in the kernel image to change.
Note that rdev -s is a synonym for swapdev.
Option
- -o offset
Synonymous to specifying an offset as an argument.
|
swapoff | swapoff -a | device ... System administration command.
Stop making the listed devices
available for swapping and paging.
Option
- -a
Consult /etc/fstab for devices marked sw.
Use those in place of the device argument.
|
swapon | swapon [options] device ... System administration command.
Make the listed devices
available for swapping and paging.
Options
- -a
Consult /etc/fstab for devices marked sw.
Use those in place of the device argument.
- -p priority
Specify a priority for the swap area. Higher priority areas
will be used up before lower priority areas are used.
|
sync | sync System administration command.
Write filesystem buffers to disk.
sync executes the sync() system
call. If the system is to be stopped, sync must be called to
ensure filesystem integrity. Note that shutdown automatically
calls sync before shutting down the system. sync may take
several seconds to complete, so the system should be told to
sleep briefly if you are about to manually call halt
or reboot. Note that shutdown is the preferred way to
halt or reboot your system, since it takes care of sync-ing
and other housekeeping for you.
|
sysklogd | sysklogd System administration command.
sysklogd, the Linux program that provides syslogd
functionality, behaves exactly like the BSD version of syslogd.
The difference should be completely transparent to the user. However,
sysklogd is coded very differently and supports a slightly
extended syntax. It is invoked as syslogd. See also
klogd.
Options
- -d
Turn on debugging.
- -f configfile
Specify alternate configuration file.
- -h
Forward messages from remote hosts to forwarding hosts.
- -l hostlist
Specify hostnames that should be logged with just their hostname, not
their fully qualified domain name. Multiple hosts should be separated
with a colon (:).
- -m markinterval
Select number of minutes between mark messages.
- -n
Avoid autobackgrounding. This is needed when starting syslogd from
init.
- -p socket
Send log to socket instead of /dev/log.
- -r
Receive messages from the network using an Internet domain socket with the
syslog service.
- -s domainlist
Strip off domain names specified in domainlist before logging. Multiple
domain names should be separated by a colon (:).
|
syslogd | syslogd TCP/IP command. Log system messages
into a set of files described
by the configuration file /etc/syslog.conf. Each message is one line.
A message can contain a priority code, marked by a number in angle braces at
the beginning of the line. Priorities are defined in <sys/syslog.h>.
syslogd reads from an Internet domain socket specified in
/etc/services. To bring syslogd down, send it a terminate signal.
|
systat | systat [options] host System administration command.
Get information about the network or system status of a remote
host by querying its netstat, systat, or daytime
service.
Options
- -n, --netstat
Specifically query the host's netstat service.
- -p port, --port port
Specify port to query.
- -s, --systat
Specifically query the host's systat service.
- -t, --time
Specifically query the host's daytime service.
|
tac | tac [options] [file] Named for the common command cat, tac prints files in
reverse. Without a filename or with -, it reads from standard
input. By default, it reverses the order of the lines, printing the
last line first.
Options
- -b, --before
Print separator (by default a newline) before string that it delimits.
- -r, --regex
Expect separator to be a regular expression.
- -s string, --separator=string
Specify alternate separator (default is newline).
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
|
tail | tail [options] [file] Print the last 10 lines of the named file
(or standard input if - is specified) on standard output.
Options
- -n[k]
Begin printing at nth item from end-of-file. k specifies
the item to count: l (lines, the default), b (blocks),
or c (characters).
- -k
Same as -n, but use the default count of 10.
- +n[k]
Like -n, but start at nth item from beginning of file.
- +k
Like -k, but count from beginning of file.
- -c num{bkm}, --bytes num{bkm}
Print last num bytes. An alternate blocksize may be
specified:
- b
512 bytes
- k
1 kilobyte
- m
1 megabyte
- -f
Don't quit at the end of file; "follow" file as it grows.
End when user presses Ctrl-C.
- -n num, --lines num
Print last num lines.
- -q, --quiet, --silent
Suppress filename headers.
- --version
Print version information and then exit.
Examples
Show the last 20 lines containing instances of .Ah:
grep '\.Ah' file | tail -20
Show the last 10 characters of variable name:
echo "$name" | tail -c
Print the last two blocks of bigfile:
tail -2b bigfile
|
talk | talk person [ttyname] Talk to another user.
person is either the login name of someone
on your own machine or user@host on another host. To
talk to a user who is logged in more than once, use ttyname
to indicate the appropriate terminal name. Once communication
has been established, the two parties may type simultaneously,
with their output appearing in separate windows. To redraw the screen,
type Ctrl-L. To exit, type your interrupt character; talk then
moves the cursor to the bottom of the screen and restores the
terminal.
|
talkd | talkd [option] TCP/IP command. Remote user communication server. talkd notifies a user
that somebody else wants to initiate a conversation. A talk
client initiates a rendezvous by sending a CTL_MSG
of type LOOK_UP to the server. This causes the server to search its
invitation tables for an existing invitation for the
client. If the lookup fails, the caller sends an ANNOUNCE message,
causing the server to broadcast an announcement on the callee's login
ports requesting contact. When the callee responds, the local server
responds with the rendezvous address, and a stream connection is
established through which the conversation takes place.
Option
- -d
Write debugging information to the syslogd log file.
|
tar | tar [options] [tarfile] [other-files] Copy files to or restore files from an archive medium.
If any files are directories, tar acts on the entire subtree.
Options need not be preceded by - (though they may be).
The exception to this rule is when you are using a long-style
option (such as --modification-time). In that case, the exact syntax is:
tar --long-option -function-options files
For example:
tar --modification-time -xvf tarfile.tar
Function options
You must use exactly one of these, and it must come before any other options:
- -c, --create
Create a new archive.
- -d, --compare
Compare the files stored in tarfile with other-files.
Report any differences: missing files, different sizes, different file
attributes (such as permissions or modification time).
- -r, --append
Append other-files to the end of an existing archive.
- -t, --list
Print the names of other-files if they are stored on the archive
(if other-files are not specified, print names of all files).
- -u, --update
Add files if not in the archive or if modified.
- -x, --extract, --get
Extract other-files from an archive (if other-files are not
specified, extract all files).
- -A, --catenate, --concatenate
Concatenate a second tar file on to the end of the first.
Options
- n
Select device n, where n is 0,...,9999. The default
is found in /etc/default/tar.
- [drive][density]
Set drive (0-7) and storage density (l, m, or h,
corresponding to low, medium, or high).
- --atime-preserve
Preserve original access time on extracted files.
- -b, --block-size=n
Set block size to n × 512 bytes.
- --checkpoint
List directory names encountered.
- --exclude=file
Remove file from any list of files.
- -f arch, --file=filename
Store files in or extract files from archive arch.
Note that filename may take the form
hostname:filename.
- --force-local
Interpret filenames in the form hostname:filename as local files.
- -g, --listed-incremental
Create new-style incremental backup.
- -h, --dereference
Dereference symbolic links.
- -i, --ignore-zeros
Ignore zero-sized blocks (i.e., EOFs).
- --ignore-failed-read
Ignore unreadable files to be archived. Default behavior is to
exit when encountering these.
- -k, --keep-old-files
When extracting files, do not overwrite files with similar names.
Instead, print an error message.
- -l, --one-file-system
Do not archive files from other file systems.
- -m, --modification-time
Do not restore file modification times;
update them to the time of extraction.
- --null
Allow filenames to be null-terminated with -T. Override -C.
- --old, --portability, --preserve
Equivalent to invoking both the -p and -s options.
- -p, --same-permissions, --preserve-permissions
Keep ownership of extracted files same as that of original permissions.
- --remove-files
Remove originals after inclusion in archive.
- --rsh-command=command
Do not connect to remote host with rsh; instead, use command.
- -s, --same-order, --preserve-order
When extracting, sort filenames to correspond to the order in the archive.
- --totals
Print byte totals.
- --use-compress-program=program
Compress archived files with program, or uncompress extracted
files with program.
- -v, --verbose
Verbose. Print filenames as they are added or extracted.
- -w, --interactive
Wait for user confirmation (y) before taking any actions.
- -z, --gzip, --ungzip
Compress files with gzip before archiving them, or uncompress them with
gunzip before extracting them.
- -C, --directory=directory
cd to directory before beginning tar operation.
- -F, --info-script, --new-volume-script=script
Implies -M (multiple archive files). Run script at the end of each file.
- -G, --incremental
Create old-style incremental backup.
- -K file, --starting-file file
Begin tar operation at file file in archive.
- -L, --tape-length=length
Write a maximum of length × 1024 bytes to each tape.
- -M, --multivolume
Expect archive to multivolume. With -c, create such an archive.
- -N date, --after-date date
Ignore files older than date.
- -O, --to-stdout
Print extracted files on standard out.
- -P, --absolute-paths
Do not remove initial slashes (/) from input filenames.
- -R, --record-number
Display archive's record number.
- -S, --sparse
Treat short file specially and more efficiently.
- -T filename, --files-from filename
Consult filename for files to extract or create.
- -V name, --label=name
Name this volume name.
- -W, --verify
Check archive for corruption after creation.
- -X file, --exclude file
Consult file for list of files to exclude.
- -Z, --compress, --uncompress
Compress files with compress before archiving them, or
uncompress them with uncompress before extracting them.
Examples
Create an archive of /bin and /usr/bin (c),
show the command working (v), and store on the tape in /dev/rmt0:
tar cvf /dev/rmt0 /bin /usr/bin
List the tape's contents in a format like ls -l:
tar tvf /dev/rmt0
Extract the /bin directory:
tar xvf /dev/rmt0 /bin
Create an archive of the current directory and store it
in a file backup.tar:
tar cvf - `find . -print > backup.tar
(The - tells tar to store the archive on standard output, which is then redirected.)
|
tcpd | tcpd TCP/IP command. Monitor incoming TCP/IP requests (such as those for
telnet, ftp, finger, exec, rlogin).
Provide checking and logging services; then pass the
request to the appropriate daemon.
|
tcpdchk | tcpdchk [options] TCP/IP command. Consult the TCP wrapper configuration (in
/etc/hosts.allow and /etc/hosts.deny); display a list of
all possible problems with it; attempt to suggest possible
fixes.
Options
- -a
Include a list of rules; do not require an ALLOW
keyword before allowing sites to access the local host.
- -d
Consult ./hosts.allow and ./hosts.deny instead
of /etc/hosts.allow and /etc/hosts.deny.
- -i conf-file
Specify location of inetd.conf or tlid.conf file. These are files that tcpdchk automatically uses in
its evaluation of TCP wrapper files.
- -v
Verbose mode.
|
tcpdmatch | tcpdmatch [options] daemon client TCP/IP command. Predict the TCP wrapper's response to a specific request.
You must specify which daemon the request is made to
(the syntax may be daemon@host for requests
to remote machines) and the client from which the
request originates (the syntax may be user@client
for a specific user or a wildcard).
Consult /etc/hosts.allow and /etc/hosts.deny to
determine the TCP wrapper's actions.
Options
- -d
Consult ./hosts.allow and ./hosts.deny instead
of /etc/hosts.allow and /etc/hosts.deny.
- -i conf-file
Specify location of inetd.conf or tlid.conf file.
These are files that tcpdmatch automatically uses in
its evaluation of TCP wrapper files.
|
tcsh | tcsh [options] [file [arguments]] An extended version of the C shell, a command interpreter
into which all other commands are entered. For more information,
see Chapter 8, "csh and tcsh".
|
tee | tee [options] files Accept output from another command and send it both to the standard
output and to files (like a T or fork in a road).
Options
- -a, --append
Append to files; do not overwrite.
- -i, --ignore-interrupts
Ignore interrupt signals.
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
Example
ls -l | tee savefile View listing and save for later
|
telinit | telinit [option] [runlevel] System administration command.
Signal init to change the system's runlevel.
telinit is actually just a link to init, the
ancestor of all processes.
Option
- -t seconds
Send SIGKILL seconds after SIGTERM. Default is 20.
Runlevels
The default runlevels vary from
distribution to distribution, but these are standard:
- 0
Halt the system.
- 1, s, S
Single user.
- 6
Reboot the system.
- a, b, c
Process only entries in /etc/inittab that are marked
with run level a, b, or c.
- q, Q
Reread /etc/inittab.
Check the /etc/inittab file for runlevels on your system.
|
telnet | telnet [options] [host [port ]] Access remote systems. telnet is the user interface that
communicates with another host using the Telnet protocol. If
telnet is invoked without host, it enters command mode, indicated
by its prompt, telnet>, and accepts and executes the commands
listed after the following options.
If invoked with arguments, telnet performs an
open command (shown in the following list) with those arguments. host
indicates the host's official name. port indicates a port number
(default is the Telnet port).
Options
- -a
Automatic login into the remote system.
- -d
Turn on socket-level debugging.
- -e [escape_char]
Set initial telnet escape character to escape_char. If
escape_char is omitted, there will be no predefined escape
character.
- -l user
When connecting to remote system and if remote system understands
ENVIRON, send user to the remote system as the value for
variable USER.
- -n tracefile
Open tracefile for recording the trace information.
- -r
Emulate rlogin: the default escape
character is a tilde (~); an escape character followed by
a dot causes telnet to disconnect from the
remote host; a ^Z instead of a dot
suspends telnet; and a ] (the default telnet
escape character) generates a normal telnet prompt. These codes are accepted only at the beginning of a line.
- -8
Request 8-bit operation.
- -E
Disable the escape character functionality.
- -L
Specify an 8-bit data path on output.
- -S tos
Set the IP type-of-service (TOS) option for the Telnet
connection to the value tos.
Commands
- CTRL-Z
Suspend telnet.
- ! [command]
Execute a single command in a subshell on the local system. If
command is omitted, an interactive subshell will be invoked.
- ? [command]
Get help. With no arguments, print a help summary. If a command is
specified, print the help information for just that command.
- close
Close a Telnet session and return to command mode.
- display argument ...
Display all, or some, of the set and toggle values.
- environ [arguments [...]]
Manipulate variables that may be sent through the TELNET
ENVIRON option. Valid arguments for environ are:
- ?
Get help for the environ command.
- define variable value
Define variable to have a value of value.
- undefine variable
Remove variable from the list of en
vi
ronment variables.
- export variable
Mark variable to have its value exported to the remote side.
- unexport variable
Mark variable to not be exported unless explicitly
requested by the remote side.
- list
Display current variable values.
- logout
If the remote host supports the logout command,
close the telnet session.
- mode [type]
Depending on state of Telnet session, type is one of
several options:
- ?
Print out help information for the mode command.
- character
Disable TELNET LINEMODE option, or, if remote side does not
understand the option, enter "character-at-a-time" mode.
- [-]edit
Attempt to [disable] enable the EDIT mode of the TELNET
LINEMODE option.
- [-]isig
Attempt to [disable]enable the TRAPSIG mode of the
LINEMODE option.
- line
Enable LINEMODE option, or, if remote side does not
understand the option, attempt to enter "old line-by-line" mode.
- [-]softtabs
Attempt to [disable] enable the SOFT_TAB mode of the
LINEMODE option.
- [-]litecho
[Disable]enable LIT_ECHO mode.
- open[-l user] host [port]
Open a connection to the named host. If no port number is
specified, attempt to contact a Telnet server at the default
port.
- quit
Close any open Telnet session and then exit telnet.
- status
Show current status of telnet. This includes the peer one is
connected to as well as the current mode.
- send arguments
Send one or more special character sequences to the remote host.
Following are the arguments that may be specified:
- ?
Print out help information for send command.
- abort
Send Telnet ABORT sequence.
- ao
Send Telnet AO sequence, which should cause the remote system
to flush all output from the
remote system to the user's terminal.
- ayt
Send Telnet AYT (Are You There) sequence.
- brk
Send Telnet BRK (Break) sequence.
- do cmd
- dont cmd
- will cmd
- wont cmd
Send Telnet DO cmd sequence, where cmd is
a number between 0 and 255 or a symbolic name for
a specific telnet command. If cmd is ?
or help, this command prints out help (including
a list of symbolic names).
- ec
Send Telnet EC (Erase Character) sequence, which
causes the remote system to erase the last character entered.
- el
Send Telnet EL (Erase Line) sequence, which causes the
remote system to erase the last line entered.
- eof
Send Telnet EOF (End Of File) sequence.
- eor
Send Telnet EOR (End Of Record) sequence.
- escape
Send current Telnet escape character (initially ^).
- ga
Send Telnet GA (Go Ahead) sequence.
- getstatus
If the remote side supports the Telnet STATUS command,
getstatus sends the subnegotiation request that the server send
its current option status.
- ip
Send Telnet IP (Interrupt process) sequence, which causes
the remote system to abort the currently running process.
- nop
Send Telnet NOP (No operation) sequence.
- susp
Send Telnet SUSP (Suspend process) sequence.
- synch
Send Telnet SYNCH sequence, which
causes the remote system to discard all previously typed (but
not read) input.
- set argument value
- unset argument value
Set any one of a number of telnet
variables to a specific value or to TRUE. The special value off
disables the function associated with the variable. unset
disables any of the specified functions. The values of variables may be
interrogated with the aid of the display command. The variables
that may be specified are:
- ?
Display legal set and unset commands.
- ayt
If telnet is in LOCALCHARS mode, this character is
taken to be the alternate AYT character.
- echo
This is the value (initially ^E) which, when in "line-by-line"
mode, toggles between doing local echoing of entered characters
and suppressing echoing of entered characters.
- eof
If telnet is operating in LINEMODE or in the old
"line-by-line" mode, entering this character as the first
character on
a line will cause the character to be sent to the remote system.
- erase
If telnet is in LOCALCHARS mode and operating in the
"character-at-a-time" mode, then when this character is entered,
a Telnet EC sequence will be sent to the remote system.
- escape
This is the Telnet escape character (initially ^[), which
causes entry into the Telnet command
mode when connected to a remote
system.
- flushoutput
If telnet is in LOCALCHARS mode and the flushoutput
character is entered, a Telnet AO sequence is sent to the remote
host.
- forw1
If Telnet is in LOCALCHARS mode, this character is taken to be
an alternate end-of-line character.
- forw2
If Telnet is in LOCALCHARS mode, this character is taken to be
an alternate end-of-line character.
- interrupt
If Telnet AO is in LOCALCHARS mode and the interrupt
character is entered, a Telnet IP sequence is sent to the
remote host.
- kill
If Telnet IP is in LOCALCHARS mode and operating
in the "character-at-a-time" mode, then when this character
is entered, a Telnet EL sequence is sent to the
remote system.
- lnext
If Telnet EL is in LINEMODE or in the
old "line-by-line" mode, then this character is taken to be
the terminal's lnext character.
- quit
If Telnet EL is in LOCALCHARS mode
and the quit character is entered, a Telnet BRK
sequence is sent to the remote host.
- reprint
If Telnet BRK is in LINEMODE or in the
old "line-by-line" mode, this character is taken to be
the terminal's reprint character.
- rlogin
Enable rlogin mode. Same as using -r command-line option.
- start
If the Telnet TOGGLE-FLOW-CONTROL option has been enabled,
this character is taken to be the terminal's start character.
- stop
If the Telnet TOGGLE-FLOW-CONTROL option has been enabled,
this character is taken to be the terminal's stop character.
- susp
If Telnet is in LOCALCHARS mode, or if the LINEMODE
is enabled and the suspend character is entered, a Telnet SUSP
sequence is sent to the remote host.
- tracefile
File to which output generated by netdata is written.
- worderase
If Telnet BRK is in LINEMODE or in the
old "line-by-line" mode, this character is taken to be
the terminal's worderase character.
Defaults for these are the terminal's defaults.
- slc [state]
Set state of special characters when Telnet LINEMODE option
has been enabled.
- ?
List help on the slc command.
- check
Verify current settings for current special characters. If discrepancies
are discovered, convert local settings to match remote ones.
- export
Switch to local defaults for the special characters.
- import
Switch to remote defaults for the special characters.
- toggle arguments [...]
Toggle various flags that control how Telnet responds to events. The
flags may be set explicitly to true or false using the set and
unset commands listed previously. The valid arguments are:
- ?
Display legal toggle commands.
- autoflush
If autoflush and LOCALCHARS are both true, then
when the ao or quit characters are recognized, Telnet
refuses to display any data on the user's terminal until the
remote system acknowledges that it has processed those Telnet sequences.
- autosynch
If autosynch and LOCALCHARS are both true, then
when the intr or quit character is entered, the
resulting Telnet sequence sent is followed by the Telnet SYNCH
sequence. Initial value for this toggle is false.
- binary
Enable or disable the Telnet BINARY option on both the input and
the output.
- inbinary
Enable or disable the Telnet BINARY option on the input.
- outbinary
Enable or disable the Telnet BINARY option on the output.
- crlf
If this toggle value is true, carriage returns
are sent as CR-LF. If false, carriage returns are
sent as CR-NUL. Initial value is false.
- crmod
Toggle carriage return mode. Initial value is false.
- debug
Toggle socket level debugging mode. Initial value is false.
- localchars
If the value is true,
flush, interrupt, quit, erase, and
kill characters are recognized locally, then transformed into
appropriate Telnet control sequences. Initial value is
true.
- netdata
Toggle display of all network data. Initial value is false.
- options
Toggle display of some internal telnet protocol processing
pertaining to Telnet options. Initial value is
false.
- prettydump
When netdata is enabled, and if prettydump is
enabled, the output from the netdata command is reorganized into
a more user-friendly format, spaces are put between each character in
the output, and an asterisk precedes any Telnet escape sequence.
- skiprc
Toggle whether to process ~/.telnetrc file.
Initial value is false, meaning the file is processed.
- termdata
Toggle printing of hexadecimal terminal data. Initial value is false.
- z
Suspend telnet; works only for the csh.
|
telnetd | telnetd [options] TCP/IP command. Telnet protocol server.
telnetd is invoked by the Internet
server for requests to connect to the
Telnet port (port 23 by default).
telnetd allocates a pseudoterminal device
for a client, thereby creating a login process that has the
slave side of the pseudoterminal serving as stdin, stdout,
and stderr. telnetd manipulates the master side
of the pseudoterminal by implementing the Telnet protocol
and by passing characters between the remote client and the login
process.
Options
- -debug [port]
Start telnetd manually instead of through inetd.
port may be specified as an alternate TCP port number on which to
run telnetd.
- -D modifier(s)
Debugging mode. This allows telnet
to print out debugging information to the connection, enabling
the user to see what telnet is doing. Several modifiers
are available for the debugging mode:
- exercise
Has not been implemented yet.
- netdata
Display data stream received by telnetd.
- options
Print information about the negotiation of the Telnet options.
- ptydata
Display data written to the pseudo terminal device.
- report
Print options information, as well as some additional
information about what processing is going on.
|
test | test expression [expression] Also exists as a built-in in most shells.
Evaluate an expression and, if its value is true, return a zero
exit status; otherwise, return a nonzero exit status.
In shell scripts, you can use the alternate form [expression].
This command is generally used with conditional constructs in shell
programs.
File testers
The syntax for all of these options is test option file.
If the specified file does not exist, they return false. Otherwise,
they will test the file as specified in the option description.
- -b
Is the file block special?
- -c
Is the file character special?
- -d
Is the file a directory?
- -e
Does the file exist?
- -f
Is the file a regular file?
- -g
Does the file have the set-group-ID bit set?
- -k
Does the file have the sticky bit set?
- -L
Is the file a symbolic link?
- -p
Is the file a named pipe?
- -r
Is the file readable by the current user?
- -s
Is the file nonempty?
- -S
Is the file a socket?
- -t [file-descriptor]
Is the file associated with file-descriptor (or 1, standard
output, by default) connected to a terminal?
- -u
Does the file have the set-user-ID bit set?
- -w
Is the file writable by the current user?
- -x
Is the file executable?
- -O
Is the file owned by the process's effective user ID?
- -G
Is the file owned by the process's effective group ID?
File comparisons
The syntax for file comparisons is test file1 option file2.
A string by itself, without options, returns true if it's at least
one character long.
- -nt
Is file1 newer than file2? Check modification, not creation, date.
- -ot
Is file1 older than file2? Check modification, not creation, date.
- -ef
Do the files have identical device and inode numbers?
String tests
The syntax for string tests is test option string.
- -z
Is the string 0 characters long?
- -n
Is the string at least 1 character long?
- = string
Are the two strings equal?
- != string
Are the strings unequal?
Expression tests
Note that an expression can consist of any of the
previous tests.
- ! expression
Is the expression false?
- expression -a expression
Are the expressions both true?
- expression -o expression
Is either expression true?
Integer tests
The syntax for integer tests is test integer1 option integer2.
You may substitute -l string for an integer; this evaluates to
string's length.
- -eq
Are the two integers equal?
- -ne
Are the two integers unequal?
- -lt
Is integer1 less than integer2?
- -le
Is integer1 less than or equal to integer2?
- -gt
Is integer1 greater than integer2?
- -ge
Is integer1 greater than or equal to integer2?
|
tftp | tftp [host [port]] User interface to the TFTP (Trivial File Transfer Protocol), which allows users to transfer files to and from a remote
machine. The remote host may be specified, in which case
tftp uses host as the default host for future transfers.
Commands
Once tftp is running, it issues the prompt:
tftp>
and recognizes the following commands:
- ? [command-name...]
Print help information.
- ascii
Shorthand for mode ASCII.
- binary
Shorthand for mode binary.
- connect hostname [port]
Set the hostname, and optionally
the port, for transfers.
- get
filename
- get remotename localname
- get filename1 filename2 filename3...filenameN
Get a file or set of files from the specified remote sources.
- mode transfer-mode
Set the mode for transfers. transfer-mode may be
ASCII or binary. The default is ASCII.
- put
filename
- put localfile remotefile
- put filename1 filename2...filenameN remote-directory
Transfer a file or set of files to the specified remote file
or directory.
- quit
Exit tftp.
- rexmt retransmission-timeout
Set the per-packet retransmission timeout, in seconds.
- status
Print status information: whether tftp is
connected to a remote host
(i.e., whether a host has been specified for the next connection),
the current mode, whether verbose and tracing modes are on, and the
values for retransmission timeout and
total transmission timeout.
- timeout total-transmission-timeout
Set the total transmission timeout, in seconds.
- trace
Toggle packet tracing.
- verbose
Toggle verbose mode.
|
tftpd | tftpd [homedir] TCP/IP command. Trivial File Transfer Protocol server.
tftpd is normally
started by inetd and operates at the port
indicated in the tftp Internet service description in the
/etc/inetd.conf file. By default, the entry for tftpd in
/etc/inetd.conf is commented out; the comment character
must be deleted to make tfptd operational. Before responding
to a request, the server attempts to change its current directory
to homedir; the default value is tftpboot.
|
tload | tload [options] [tty] Display system load average in graph format.
If tty is specified, print it to that tty.
Options
- -d delay
Specify the delay, in seconds, between updates.
- -s scale
Specify scale (number of characters between each graph tick).
A smaller number results in a larger scale.
|
top | top [options] Provide information (frequently refreshed) about the most
CPU-intensive processes currently running.
See ps for explanations of the
field descriptors.
Options
- -b
Run in batch mode; don't accept command-line input. Useful for
sending output to another command or to a file.
- -c
Show command line in display instead of just command name.
- -d delay
Specify delay between refreshes.
- -i
Suppress display of idle and zombie processes.
- -n num
Update display num times, then exit.
- -p pid
Monitor only processes with the specified process ID.
- -q
Refresh without any delay. If user is privileged, run with highest priority.
- -s
Secure mode. Disable some (dangerous) interactive commands.
- -S
Cumulative mode. Print total CPU time of each process, including dead
child processes.
Interactive commands
- space
Update display immediately.
- c
Toggle display of command name or full command line.
- f, F
Add fields to display or remove fields from the display.
- h, ?
Display help about commands and the status of secure and
cumulative modes.
- k
Prompt for process ID to kill and signal to send (default is 15) to
kill it.
- i
Toggle suppression of idle and zombie processes.
- l
Toggle display of load average and uptime information.
- m
Toggle display of memory information.
- n, #
Prompt for number of processes to show.
If 0 is entered, show as many as will fit on the screen
(default).
- o, O
Change order of displayed fields.
- q
Exit.
- r
Apply renice to a process. Prompt for PID and
renice value. Suppressed in secure mode.
- s
Change delay between refreshes. Prompt for new delay time,
which should be in seconds. Suppressed in secure mode.
- t
Toggle display of processes and CPU states
information.
- A
Sort by age, with newest first.
- ^L
Redraw screen.
- M
Sort tasks by resident memory usage.
- N
Sort numerically by process ID.
- P
Sort tasks by CPU usage (default).
- S
Toggle cumulative mode. (See the
-S option.)
- T
Sort tasks by time/cumulative time.
- W
Write current setup to ~/.toprc. This is the
recommended way to write a top
configuration file.
|
touch | touch [options] files For one or more files, update the access time and
modification time (and dates) to the current time and date.
touch is useful in forcing other
commands to handle files a certain way; e.g., the operation
of make, and sometimes
find,
relies on a file's access and modification time. If a file doesn't exist,
touch creates it with a filesize of 0.
Options
- -a, --time=atime, --time=access, --time=use
Update only the access time.
- -c, --no-create
Do not create any file that doesn't already exist.
- -d time, --date time
Change the time value to the specified time instead of
the current time. time can use several formats and
may contain month names, time zones, a.m. and p.m. strings, as well as others.
- -m, --time=mtime, --time=modify
Update only the modification time.
- -r file, --reference file
Change times to be the same as those of the specified
file, instead of the current time.
- -t time
Use the time specified in time instead of the current
time. This argument must be of the
format: [[cc]yy]mmddhhmm[.ss],
indicating optional century and year, month, date, hours, minutes,
and optional
seconds.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
|
tr | tr [options] [string1 [string2]] Translate characters -- copy standard input to standard output, substituting
characters from string1 to string2
or deleting characters in string1.
Options
- -c, --complement
Complement characters in string1 with respect to
ASCII 001-377.
- -d, --delete
Delete characters in string1 from output.
- -s, --squeeze-repeats
Squeeze out repeated output characters in string2.
- -t, --truncate-set1
Truncate string1 to the length of
string2 before translating.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
Special characters
Include brackets ([]) where shown.
- \a
^G (bell)
- \b
^H (backspace)
- \f
^L (form feed)
- \n
^J (newline)
- \r
^M (carriage return)
- \t
^I (tab)
- \v
^K (vertical tab)
- \nnn
Character with octal value nnn.
- \\
Literal backslash.
- char1-char2
All characters in the range char1 through
char2.
If char1 does not sort before char2,
produce an error.
- [char1-char2]
Same as char1-char2 if
both strings use this.
- [char*]
In string2, expand char to the
length of string1.
- [char*number]
Expand char to number
occurrences. [x*4]
expands to xxxx, for instance.
- [:class:]
Expand to all characters in class, where
class can be:
- alnum
Letters and digits
- alpha
Letters
- blank
Whitespace
- cntrl
Control characters
- digit
Digits
- graph
Printable characters except space
- lower
Lowercase letters
- print
Printable characters
- punct
Punctuation
- space
Whitespace (horizontal or vertical)
- upper
Uppercase letters
- xdigit
Hexadecimal digits
- [=char=]
The class of characters in which char belongs.
Examples
Change uppercase to lowercase in a file:
cat file | tr '[A-Z]' '[a-z]'
Turn spaces into newlines (ASCII code 012):
tr ' ' '\012' < file
Strip blank lines from file and save in new.file
(or use 011 to change successive tabs into one tab):
cat file | tr -s "" "\012" > new.file
Delete colons from file; save result in new.file:
tr -d : < file > new.file
|
traceroute | traceroute [options] host [packetsize] TCP/IP command.
Trace route taken by packets to reach network host. traceroute
attempts tracing by launching UDP probe packets with a small
TTL (time to live), then listening for an ICMP "time exceeded"
reply from a gateway. host is the destination hostname or the IP
number of host to reach. packetsize is the packet size in bytes
of the probe datagram. Default is 38 bytes.
Options
- -d
Turn on socket-level debugging.
- -g addr
Enable the IP LSRR (Loose Source Record Route) option in addition to
the TTL tests, to ask how someone at IP address addr can
reach a particular target.
- -l
Include the time-to-live value for each packet received.
- -m max_ttl
Set maximum time-to-live used in outgoing probe packets to
max-ttl hops. Default is 30 hops.
- -n
Show numerical addresses; do not look up hostnames. (Useful if DNS is not functioning properly.)
- -p port
Set base UDP port number used for probe packets to port. Default
is (decimal) 33434.
- -q n
Set number of probe packets for each time-to-live setting to the value
n. Default is 3.
- -r
Bypass normal routing tables and send directly to a host on an attached
network.
- -s src_addr
Use src_addr as the IP address that will serve as the source address
in outgoing probe packets.
- -t tos
Set the type-of-service in probe packets to tos
(default 0). The value must be a decimal integer in the range 0 to
255.
- -v
Verbose -- received ICMP packets (other than TIME_EXCEEDED and
PORT_UNREACHABLE) will be listed.
- -w wait
Set time to wait for a response to an outgoing probe packet to
wait seconds (default is 3 seconds).
|
troff | troff See groff.
|
true | true A null command that returns a successful (0) exit status.
See also false.
|
tune2fs | tune2fs [options] device System administration command.
Tune the parameters of a Linux Second Extended Filesystem
by adjusting various parameters. You must specify the
device on which the filesystem resides; it must not
be mounted read/write when you change its parameters.
Options
- -c mount-counts
Specify the maximum number of mount counts between two checks on the
filesystem.
- -e behavior
Specify the kernel's behavior when encountering errors.
behavior must be one of:
- continue
Continue as usual.
- remount-ro
Remount the offending filesystem in read-only mode.
- panic
Cause a kernel panic.
- -g group
Allow group (a group ID or name) to use reserved blocks.
- -i interval[d|w|m]
Specify the maximum interval between filesystem checks. Units may be
in days (d), weeks (w), or months
(m).
If interval is 0, checking will not be time-dependent.
- -l
Display a list of the superblock's contents.
- -m percentage
Specify the percentage of blocks that will be reserved for use by
privileged users.
- -r num
Specify the number of blocks that will be reserved for use by
privileged users.
- -u user
Allow user (a user ID or name) to use reserved blocks.
|
tunelp | tunelp device [options] System administration command.
Control a lineprinter's device parameters.
Without options, print information about device(s).
Options
- -a [on|off]
Specify whether or not to abort if the printer encounters an error.
By default, do not abort.
- -c n
Retry device n times if it refuses a character. (Default is 250.)
After exhausting n, sleep before retrying.
- -i irq
Use irq for specified parallel port. Ignore -t and -c.
If 0, restore noninterrupt driven (polling) action.
- -o [on|off]
Specify whether to abort if device is not online or is out of paper.
- -q [on|off]
Specify whether to print current IRQ setting.
- -r
Reset port.
- -s
Display printer's current status.
- -t time
Specify a delay of time in jiffies to sleep before resending
a refused character to the device. A jiffy is defined as either one
tick of the system clock or one AC cycle time; it should be approximately
1/100th of a second.
- -w time
Specify a delay of time in jiffies to sleep before resending
a strobe signal.
- -C [on|off]
Specify whether to be extremely careful in checking for printer error.
|
ul | ul [options] [names] Translate underscores to underlining.
The correct sequence with which to do this will vary by terminal
type. Some terminals are unable to handle underlining.
Options
- -i
Translate -, when on a separate line, to underline, instead of
translating underscores.
- -t terminal-type
Specify terminal type. By default, TERM is consulted.
|
umount | umount [options] [special-device/directory] System administration command.
Unmount a filesystem. umount announces to the system that the
removable file structure previously mounted on device
special-device is to be removed. umount also works
by specifying the directory. Any pending I/O for the
filesystem is completed, and the file structure is flagged as clean.
Options
- -a
Unmount all filesystems that are listed in /etc/mtab.
- -n
Unmount, but do not record changes in /etc/mtab.
- -t type
Unmount only filesystems of type type.
|
uname | uname [options] Print information about the machine and operating system.
Without options, print the name of the operating system (Linux).
Options
- -a, --all
Combine all the system information from the other options.
- -m, --machine
Print the hardware the system is running on.
- -n, --nodename
Print the machine's hostname.
- -r, --release
Print the release number of the kernel.
- -s, --sysname
Print the name of the operating system (Linux).
- -p, --processor
Print the type of processor (not available on all versions).
- -v
Print build information about the kernel.
- --help
Display a help message and then exit.
- --version
Print version information and then exit.
|
uncompress | uncompress [options] files Uncompress files that were compressed (i.e.,
whose names end in .Z). See
compress for the available options;
uncompress takes all the same options except
-r and -b.
|
unexpand | unexpand [options] [files] Convert strings of initial whitespace, consisting of at least two
spaces and/or tabs to tabs. Read from standard input if given no
file or a file named -.
Options
- -a, --all
Convert all, not just initial, strings of spaces and tabs.
- -nums, -t nums, --tabs nums
nums is a comma-separated list of integers
that specify the placement of tab stops.
If a single integer is provided, the tab stops are set to every
integer spaces. By default, tab stops are 8
spaces apart. With -t and
--tabs, the list may be
separated by whitespace instead of commas. This option
implies -a.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
|
uniq | uniq [options] [file1 [file2]] Remove duplicate adjacent lines from sorted file1,
sending one copy of each line to file2 (or to standard output).
Often used as a filter. Specify only one of
-d
or -u. See also
comm and
sort.
Options
- -n, -f n, --skip-fields=n
Ignore first n fields of a line. Fields are separated by spaces or by tabs.
- +n, -s n, --skip-chars=n
Ignore first n characters of a field.
- -c, --count
Print each line once, prefixing number of instances.
- -d, --repeated
Print duplicate lines once but no unique lines.
- -i, --ignore-case
Ignore case differences when checking for duplicates.
- -u, --unique
Print only unique lines (no copy of duplicate entries is kept).
- -w n, --check-chars=n
Compare only first n characters per line (beginning
after skipped fields and characters).
- --help
Print a help message and then exit.
- --version
Print version information and then exit.
Examples
Send one copy of each line from list
to output file list.new:
uniq list list.new
Show which names appear more than once:
sort names | uniq -d
|
unshar | unshar [options] [files] Unpack a shell archive (shar file). unshar
scans mail messages looking for the start of a
shell archive. It then passes the archive through a copy
of the shell to unpack it. unshar
accepts multiple files. If no files are given, standard input is used.
Options
- -c, --overwrite
Overwrite existing files.
- -d directory, --directory=directory
Change to directory before unpacking any files.
- -e, --exit-0
Sequentially unpack multiple archives stored in same file; uses clue
that many shar files are terminated by
an exit 0 at the beginning of a line.
(Equivalent to -E "exit 0".)
- -E string, --split-at=string
Like -e, but allows you to specify
the string that separates archives.
- -f, --force
Same as -c.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
|
update | update [options] System administration command.
update is a daemon that controls how often the kernel's disk
buffers are flushed to disk. update is also known as
bdflush. The daemon forks a couple of processes to call system
functions flush() and sync(). When called by an
unprivileged user, no daemon is created. Instead, update
calls sync() and then exits. By default, update will
wake up every 5 seconds and flush() some dirty buffers.
If that doesn't work, it will try waking up every 30
seconds to sync()
the buffers to disk. Not all of the listed options are available in
every version of update.
Options
- -d
Display the kernel parameters. This does not start the update daemon.
- -f seconds
Call flush() at this interval. Default is 5.
- -h
Help. Print a command summary.
- -s seconds
Call sync() at this interval. Default is 30.
- -S
Always use sync() instead of flush.
- -0 percent
Flush buffers when the specified percent of the buffer cache is
dirty.
- -1 blocks
The maximum number of dirty blocks to write out per wake cycle.
- -2 buffers
The number of clean buffers to try to obtain each time the free buffers
are refilled.
- -3 blocks
Flush buffers if dirty blocks exceed blocks when trying to refill
the buffers.
- -4 percent
Percent of buffer cache to scan when looking for free clusters.
- -5 seconds
Time for a data buffer to age before being flushed.
- -6 seconds
Time for a nondata buffer to age before being flushed.
- -7 constant
The time constant to use for load average.
- -8 ratio
How low the load average can be before trimming back the number of
buffers.
|
uptime | uptime Print the current time, amount of time logged in, number of users
currently logged in (which may include the same user multiple times),
and system load averages. This output is also produced
by the first line of the w command.
|
useradd | useradd [options] [user] System administration command.
Create new user accounts or update default account information.
Unless invoked with the -D option, user must be given.
useradd will create new entries in system files. Home
directories and initial files may also be created as needed.
Options
- -c comment
Comment field.
- -d dir
Home directory. The default is to use user
as the directory name under the home directory
specified with the -D option.
- -e date
Account expiration date. date
is in the format MM/DD/YYYY. Two-digit
year fields are also accepted. The value is
stored as the number of days since January 1, 1970. This option requires the use of shadow passwords.
- -f days
Permanently disable account this many days after
the password has expired. A value of -1 disables this
feature. This option requires the use
of shadow passwords.
- -g group
Initial group name or ID number. If a different default group
has not been specified using the -D option, the default group is 1.
- -G groups
Supplementary groups given by name or number in a comma-separated
list with no whitespace.
- -k [dir]
Copy default files to user's home directory. Meaningful only when used
with the -m option. Default files are copied from
/etc/skel/ unless an alternate dir is specified.
- -m
Make user's home directory if it does not exist. The default is not to
make the home directory.
- -o
Override. Accept a nonunique uid with the -u option. (Probably a bad idea.)
- -s shell
Login shell.
- -u uid
Numerical user ID. The value must be unique unless the -o option
is used. The default value is the smallest ID value greater than 99
and greater than every other uid.
- -D [options]
Set or display defaults. If options are specified, set them.
If no options are specified, display current defaults. The options are:
- -b dir
Home directory prefix to be used in creating home directories. If the
-d option is not used when creating an account, the user name will
be appended to dir.
- -e date
Expire date. Requires the use of shadow passwords.
- -f days
Number of days after a password expires to disable an account.
Requires the use of shadow passwords.
- -g group
Initial group name or ID number.
- -s shell
Default login shell.
|
userdel | userdel [option] user System administration command.
Delete all entries for user in system account files.
Option
- -r
Remove the home directory of user and any files
contained in it.
|
usermod | usermod [options] user System administration command.
Modify user account information.
Options
- -c comment
Comment field.
- -d dir
Home directory.
- -e date
Account expiration date. date
is in the format MM/DD/YYYY. Two-digit
year fields are also accepted, but the value is
stored as the number of days since January 1, 1970.
This option requires the use of shadow passwords.
- -f days
Permanently disable account this many days after
the password has expired. A value of -1 disables this
feature. This option requires the use
of shadow passwords.
- -g group
Initial group name or number.
- -G groups
Supplementary groups given by name or number in a comma-separated
list with no whitespace.
user will be removed from any groups to which they currently belong
that are not included in groups.
- -l name
Login name. This cannot be changed while the user
is logged in.
- -o
Override. Accept a nonunique uid with the -u option.
- -s shell
Login shell.
- -u uid
Numerical user ID. The value must be unique unless the
-o option is used. Any files owned by user in
the user's home directory will have their user ID changed
automatically. Files outside of the home directory will
not be changed. user should not be executing any processes
while this is changed.
|
users | users [file] Print a space-separated list of each login session
on the host. Note that this may include the same user multiple times.
Consult file or, by default, /etc/utmp.
|
usleep | usleep [microseconds] usleep [options]
Sleep some number of microseconds (default is 1).
Options
- --help
Print help information and then exit.
- --usage
Print usage message and then exit.
- -v, --version
Print version information.
|
uudecode | uudecode [-o outfile] [file] Read a uuencoded file and re-create the original
file with the permissions and name set in the
file (see uuencode).
The -o option specifies an
alternate output file.
|
uuencode | uuencode [-m] [file] name Encode a binary file.
The encoding uses only printable ASCII characters and includes
the permissions and name of the file.
When file is reconverted via
uudecode,
the output is saved as name.
If the file argument is omitted,
uuencode can take standard
input, so a single argument is taken as the name to be given to
the file when it is decoded. With the
-m option, base64 encoding is used.
Example
It's common to encode a file and save it with an identifying
extension, such as .uue. This example encodes the binary file
flower12.jpg, names it rose.jpg, and saves it to
a .uue file:
% uuencode flower12.jpg rose.jpg > rose.uue
Encode flower12.jpg and mail it:
% uuencode flower12.jpg flower12.jpg | mail ellen@oreilly.com
|
vacation | vacation vacation [options] [user] Automatically return a mail message to the sender announcing that you are on
vacation.
Use vacation with no options to initialize the
vacation mechanism. The process performs several steps.
Creates a .forward file in your home
directory.
The .forward file contains:
\user, "|/usr/bin/vacation user"
user is your login name.
The action of this file is to actually deliver the
mail to user (i.e., you)
and to run the incoming mail through vacation. Creates the .vacation.pag
and .vacation.dir files. These files keep track of who has sent you messages, so that they
receive only one "I'm on vacation" message
from you per week. Starts an editor to edit the contents of .vacation.msg.
The contents of this file are mailed back to whomever sends you mail. Within its body, $subject is replaced with the contents
of the incoming message's Subject line.
Remove or rename the .forward file to
disable vacation processing.
Options
The
-a
and
-r
options are used within a .forward file;
see the example.
- -a alias
Mail addressed to alias is actually mail for
the user and should produce an automatic reply.
- -i
Reinitialize the .vacation.pag
and .vacation.dir files.
Use this right before leaving for your next vacation.
- -r interval
By default, no more than one message per week is sent to any sender. This option changes that interval.
interval is a number with a trailing
s,
m,
h,
d,
or
w
indicating seconds, minutes, hours, days, or weeks, respectively. If interval is infinite, only one reply is sent to each sender.
Example
Send no more than one reply every three weeks to any given sender:
$ cd
$ vacation -I
$ cat .forward
\jp, "|/usr/bin/vacation -r3w jp"
$ cat .vacation.msg
From: jp@wizard-corp.com (J. Programmer, via the vacation program)
Subject: I'm out of the office ...
Hi. I'm off on a well-deserved vacation after finishing
up whizprog 1.0. I will read and reply to your mail
regarding "$SUBJECT" when I return.
Have a nice day.
|
vi | vi [options] [files] A screen-oriented text editor based on
ex.
For more information on vi,
see Chapter 11, "The vi Editor".
|
vidmode | vidmode [option] image [mode [offset]] System administration command.
Sets the video mode for a kernel image. If no arguments are
specified, print current mode value. mode is a 1-byte value
located at offset 506 in a kernel image. You may change the
mode by specifying the kernel image to change, the
new mode, and the byte offset at which to place the new
information (the default is 506). Note that rdev -v is a synonym for
vidmode. If LILO is used, vidmode is not needed. The
video mode can be set from the LILO prompt during a boot.
Modes
- -3
Prompt
- -2
Extended VGA
- -1
Normal VGA
- 0
Same as entering 0 at the prompt
- 1
Same as entering 1 at the prompt
- 2
Same as entering 2 at the prompt
- 3
Same as entering 3 at the prompt
- n
Same as entering n at the prompt
Option
- -o offset
Same as specifying an offset as an argument.
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w | w [options] [user] Print summaries of system usage, currently logged-in users, and what
they are doing. w is essentially a combination of
uptime, who, and ps -a. Display output for
one user by specifying user.
Options
- -f
Toggle printing the from (remote hostname) field.
- -h
Suppress headings and uptime information.
- -s
Use the short format.
- -u
Ignore the username while figuring out the current
process and CPU times.
- -V
Display version information.
File
- /var/run/utmp
List of users currently logged on.
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wall | wall [file] System administration command.
Write to all users. wall reads a message from the standard input
until an end-of-file. It then sends this message to all users currently
logged in, preceded by "Broadcast Message from..."
If file is specified, read input from that, rather than from
standard input.
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wc | wc [options] [files] Print character, word, and line counts for each file. Print a total
line for multiple files.
If no files are given, read standard input.
See other examples under ls and sort.
Options
- -c, -bytes, --chars
Print character count only.
- -l, --lines
Print line count only.
- -w, --words
Print word count only.
- --help
Print help message and then exit.
- --version
Print the version number and then exit.
Examples
Count the number of users logged in:
who | wc -l
Count the words in three essay files:
wc -w essay.[123]
Count lines in the file named by
variable $file (don't display filename):
wc -l < $file
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whatis | whatis keywords Search the short manual page descriptions in the whatis
database for each keyword and print a
one-line description to standard
output for each match. Like apropos,
except that it only searches for complete words. Equivalent to
man -f.
|
whereis | whereis [options] files Locate the binary, source, and manual page files for specified
commands/files. The supplied filenames are first stripped of
leading pathname components and any (single) trailing
extension of the form .ext
(for example, .c). Prefixes
of s. resulting from use of source code control are also
dealt with. whereis then attempts to
locate the desired program in a list of standard Linux directories
(e.g., /bin,
/etc, /usr/bin,
/usr/local/bin/, etc.).
Options
- -b
Search only for binaries.
- -f
Terminate the last directory list and signal the
start of filenames; required when any of
the -B,
-M,
or -S options are used.
- -m
Search only for manual sections.
- -s
Search only for sources.
- -u
Search for unusual entries, that is, files that do not
have one entry of each requested type. Thus, the command whereis -m -u * asks for
those files in the current directory that have no
documentation.
- -B directories
Change or otherwise limit the directories to search for binaries.
- -M directory
Change or otherwise limit the directories to search for manual sections.
- -S directory
Change or otherwise limit the directories to search for sources.
Example
Find all files in /usr/bin that are not documented in
/usr/man/man1 but that have source in /usr/src:
% cd /usr/bin
% whereis -u -M /usr/man/man1 -S /usr/src -f *
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which | which [options] [--] [command] [...] List the full pathnames of the files that would be executed
if the named commands had been run.
which searches the user's
$PATH environment variable. The
C shell and tcsh have a built-in
which command that has no options.
To use the options, specify the full pathname (e.g.,
/usr/bin/which).
Options
- -a, --all
Print all matches, not just the first.
- -i, --read-alias
Read aliases from standard input and write matches to standard output. Useful
for using an alias for which.
- --skip-alias
Ignore --read-alias if
present. Useful for finding normal binaries while using --read-alias
in an alias for which.
- --skip-dot
Skip directories that start with a dot.
- --skip-tilde
Skip directories that start with a tilde (~) and
executables in $HOME.
- --show-dot
If a matching command is found in a directory that starts with a dot,
print ./cmdname instead of the full pathname.
- --show-tilde
Print a tilde (~) to indicate the user's home directory.
Ignored if the user is root.
- --tty-only
Stop processing options on the right if not on a tty.
- -v, -V, --version
Print version information and then exit.
Example
$ which cc ls
/usr/bin/cc
ls: aliased to ls -sFC
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who | who [options] [file] who am i Show who is logged in to the system. With no options,
list the names of users currently logged in, their
terminal, the time they have been logged in, and the name of the host
from which they have logged on. An optional system
file (default is /etc/utmp)
can be supplied to give additional information.
Options
- am i
Print the username of the invoking user.
- --help
Print a help message and then exit.
- -i, -u, --idle
Include idle times. An idle time of . indicates activity within the last
minute; one of old indicates no activity in
more than a day.
- -l, --lookup
Attempt to include canonical hostnames via DNS.
- -m
Same as who am i.
- -q, --count
"Quick." Display only the usernames and total number of users.
- --version
Print version information and then exit.
- -w, -T, --mesg, --message, --writable
Include user's message status:
- +
mesg y (write messages allowed)
- -
mesg n (write messages refused)
- ?
Cannot find terminal device
- -H, --heading
Print headings.
Example
This sample output was produced at 8 a.m. on April 17:
$ who -uH
NAME LINE TIME IDLE PID COMMENTS
Earvin ttyp3 Apr 16 08:14 16:25 2240
Larry ttyp0 Apr 17 07:33 . 15182
Since Earvin has been idle since yesterday afternoon
(16 hours), it appears that he isn't at work yet. He
simply left himself logged in. Larry's terminal is currently
in use.
|
whoami | whoami Print current user ID. Equivalent to
id -un.
|
write | write user [tty] message Initiate or respond to an interactive conversation with
user. A write
session is terminated with EOF. If the user is logged in
to more than one terminal, specify a tty number. See also
talk;
use mesg
to keep other users from writing to your terminal.
|
xargs | xargs [options] [command] Execute command (with any initial arguments), but
read remaining arguments from standard input
instead of specifying them directly. xargs
passes these arguments in several bundles to command,
allowing command
to process more arguments than it could normally handle at once.
The arguments are typically a long list of filenames
(generated by ls or
find, for example) that get passed to
xargs via a pipe.
Options
- -0, --null
Expect filenam |