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You may decide that you shouldn't have put a process in the background. Or you decide that the process is taking too long to execute. You can cancel a background process if you know its process ID.
The kill command aborts a process. The command's format is:
kill PID(s)
kill terminates the designated process IDs (shown under the PID heading in the ps listing). If you do not know the process ID, do a ps first to display the status of your processes.
In the following example, the "sleep n" command simply causes a process to "go to sleep" for n number of seconds. We enter two commands, sleep and who, on the same line, as a background process.
$ (sleep 60; who)& [1] 21087 $ ps PID TTY TIME COMMAND 20055 4 0:10 sh 21087 4 0:01 sh 21088 4 0:00 sleep 21089 4 0:02 ps $ kill 21088 [1]+ Terminated sleep 60 $ tom tty2 Aug 30 11:27 grace tty4 Aug 30 12:24 tim tty5 Aug 30 07:52 dale tty7 Aug 30 14:34
We decided that 60 seconds was too long to wait for the output of who. The ps listing showed that sleep had the process ID number 21088, so we used this PID to kill the sleep process. You should see a message like "terminated" or "killed"; if you don't, use another ps command to be sure the process has been killed.
The who program is executed immediately, since it is no longer waiting on sleep; it lists the users logged into the system.
In addition, if you've run an interpreted program (such as a shell script), you may not be able to kill all dependent processes by killing the interpreter process that got it all started; you may need to kill them individually. However, killing a process that is feeding data into a pipe generally kills any processes receiving that data.
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| 7.2. Checking on a Process |  | 8. Where to Go from Here |
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