Listing 2. Perl Script
#
# ws.pl -- Take data and HTML template and produce
# an output HTML file.
#
$TEMPLATE='/home/weather/WWW/wsTemplate.html';
$twentyfourhours = 86400; #seconds in a day
# Filename for today's data
$DATADIR="/home/weather/data";
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
localtime(time);
$TODAY= sprintf "%02d%02d%02d", $mon+1, $mday, $year;
$DATAFILE="$DATADIR/$TODAY";
# Calculate yesterday's filename
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
localtime(time-$twentyfourhours);
$YESTERDAY= sprintf "%02d%02d%02d", $mon+1, $mday, $year;
$MYESTERDAYFILE="$DATADIR/$YESTERDAY.max";
$mYESTERDAYFILE="$DATADIR/$YESTERDAY.min";
$CBP_CORRECTION = 6.68; # Correction for atmospheric pressure
# derived with help from local weather expert
# Match these patterns in the template file.
# Fill in the appropriate information
# from the latest data record.
# %TIME% %DATE%
# %FTEMP% (Farenheit) %CTEMP% (Celcius) %HUMIDITY%
# %BP% %CBP% (pressure and corrected pressure)
# %WSPEED% %KWSPEED% %WDIRECTION% (speed in MPH and KPH)
# %RAIN%
# YM - yesterday Max, Ym - yesterday Min
# %YMTEMP% %YmTEMP% %YMHUMIDITY% %YmHUMIDITY%
# %YRAIN%
if( -r $DATAFILE)
{
$lastline = `tail -1 $DATAFILE`;
}
else
{
die "No current datafile $DATAFILE";
}
($time, $date, $wdir, $wspeed, $aux, $intemp, $outtemp, $hum, $bp,
$raind, $rainm, $rain_rate) = split(' ',$lastline);
# Get stuff from yesterday's Max file
if( -r $MYESTERDAYFILE)
{
$maxline = `tail -1 $MYESTERDAYFILE`;
}
($Max, $Mdate, $Mwdir, $Mwspeed, $Maux, $Mintemp, $Mouttemp, $Mhum, $Mbp,
$Mraind, $Mrainm, $Mrain_rate) = split(' ',$maxline);
# Get stuff from yesterday's Min file
if( -r $mYESTERDAYFILE)
{
$minline = `tail -1 $mYESTERDAYFILE`;
}
($max, $mdate, $mwdir, $mwspeed, $maux, $mintemp, $mouttemp, $mhum, $mbp,
$mraind, $mrainm, $mrain_rate) = split(' ',$minline);
# I do some messaging of the data to remove some indicators
# and expand others.
$wspeed =~ s/MPH//;
$wdir =~ s/E/east /g;
$wdir =~ s/N/north /g;
$wdir =~ s/W/west /g;
$wdir =~ s/S/south /g;
$outtemp =~ s/F//;
$outtemp =~ s/^0//;
$Mouttemp =~ s/F//;
$Mouttemp =~ s/^0//;
$mouttemp =~ s/F//;
$mouttemp =~ s/^0//;
$intemp =~ s/F//;
$intemp =~ s/^0//;
$hum =~ s/%//;
$hum =~ s/^0//;
$mhum =~ s/%//;
$mhum =~ s/^0//;
$Mhum =~ s/%//;
$Mhum =~ s/^0//;
$bpdir = "rising" if ($bp =~ /R/);
$bpdir = "steady" if ($bp =~ /S/);
$bpdir = "falling" if ($bp =~ /F/);
$bp =~ s/[A-Z]//;
$raind =~ s/\"D//;
$Mraind =~ s/\"D//;
$rainm =~ s/\"M//;
$rain_rate =~ s/\"R//;
$outctemp = sprintf("%3.1f",ftoc($outtemp));
$dewpoint = sprintf("%3.0f",dewpoint($outtemp,$hum));
$cbp = &cbp($bp);
$kwspeed = sprintf("%2.0f", $wspeed * 1.609);
open(T,"$TEMPLATE") or die "no such file $TEMPLATE\n";
while (<T>)
{
# For each line in the template file...
# Do the actual template replacements
s/%TIME%/$time/;
s/%DATE%/$date/;
s/%FTEMP%/$outtemp/;
s/%CTEMP%/$outctemp/;
s/%HUMIDITY%/$hum/;
s/%DEWPOINT%/$dewpoint/;
s/%CBP%/$cbp $bpdir /;
s/%BP%/$bp/;
s/%WSPEED%/$wspeed/;
s/%KWSPEED%/$kwspeed/;
s/%WDIRECTION%/$wdir/;
s/%RAIN%/$raind/;
s/%YMHUMIDITY%/$Mhum/;
s/%YmHUMIDITY%/$mhum/;
s/%YMTEMP%/$Mouttemp/;
s/%YmTEMP%/$mouttemp/;
s/%YRAIN%/$Mraind/;
# Print this doctored-up line.
print $_;
}
# Subroutine for correction of atmospheric pressure
sub cbp
{
local($in) = @_;
return(sprintf("%2.2f", $in + $CBP_CORRECTION));
}
# Subroutines for F-->C and C-->F temp conversions
sub ctof
{
local ($C) = @_;
$F = (9/5 * $C) + 32;
return $F;
}
sub ftoc
{
local ($F) = @_;
$C = 5/9 * ($F - 32);
return $C;
}
# Subroutine to calculate dewpoint
sub dewpoint
{
local ($F, $H) = @_;
$rh = $H/100; # RH. Fraction, [0..1] not %.
$t = ftoc($F); #Celsius Temperature
$es = 6.112 * exp(17.67 * $t / ($t + 243.5));
$e = $rh * $es;
$loge = log($e/6.112);
$dp = 243.5 * $loge/(17.67 - $loge);
return ctof($dp);
}
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