Creating Web Plots on Demand

Listing 1. Perl Script for Web Plotting

#! /usr/bin/perl
# SECTION 1:
# Set variables for the locations and names of all
# the files.
$logfile = "/var/httpd/logs/access_log";
$httproot = "/var/httpd/htdocs/";
$imagedir = "images";
$datafile = "/tmp/gnuplot_$$.dat";
$gpfile = "/tmp/gnuplot_$$.gp";
$giffile = "gnuplot_$$.gif";
$GNUPLOT = "gnuplot";
$PPMTOGIF = "ppmtogif";

# SECTION 2:
# Get today's date in the same format as the
# server's access log.
if ($ENV{"QUERY_STRING"} =~ /[0-9]+/) {
    ($day, $mon, $year) = split ("/",<\n>
   $ENV{"QUERY_STRING"});
}
else {
    $datestr = `date`;
    chop $datestr;
    ($dow, $mon, $day, $hour,
     $min, $sec, $zone, $year) = split (/[ ]+|:/,<\n>
   $datestr);
}
$date = sprintf ("%02d/%s/%d", $day, $mon, $year);

# SECTION 3:
# Count the number of hits for the specified date.
# I scale minutes (0..59) to a value in the 0..99
# range so that gnuplot plots a contiguous graph.
# For example, the time 1:30pm would become the
# gnuplot x value 1350 (more or less).
open (LOGFILE, "< $logfile");
while (<LOGFILE>) {
    if ($_ =~ /\[$date/) {
   if ($_ =~ m/^.+\[(.+)\].+$/) {
       ($indate, $inhour,
        $inmin, $stuff) = split (":", $1);
       $hr_percent = ($inmin/60) * 100;
       $accesses[$inhour * 100 + $hr_percent]++;
       $total++;
   }
    }
}
close LOGFILE;

# SECTION 4:
# Write the data file that gnuplot will use.
open (DATAFILE, "> $datafile");
for ($i=0; $i <= 2400; $i++) {
    if (defined ($accesses[$i])) {
   printf (DATAFILE "%04d\t%d\n", $i,<\n>
   $accesses[$i]);
    }
    else {
   printf (DATAFILE "%04d\t0\n", $i);
    }
}
close DATAFILE;

# SECTION 5:
# Write the gnuplot command file.
# Define custom tic marks for the x axis.
for ($i=0; $i <=24; $i++) {
    if ($i == 12) {
        $xtics = sprintf ("%s\"%s\" %d,",
           $xtics, "Noon", $i*100);
    }
    else {
        $xtics = sprintf ("%s\"%02d\" %d,",
           $xtics, $i, $i*100);
    }
}
chop $xtics;
open (GPFILE, "> $gpfile");

# Everything after the following line up to the
# terminating "EOM" line defines the contents of
# the gnuplot command file.
print GPFILE <<EOM;
set term pbm color
set offsets
set nolog
set nopolar
set border
set grid
set title "Web Server Accesses for $mon $day, $year"
set xlabel "Time (Hours)"
set ylabel "Number of Hits"
set size 1.10, 0.50
set xtics ($xtics)
plot '$datafile' title "" with lines
EOM
close GPFILE;

# SECTION 6:
#
# Run gnuplot, and convert the output to gif
# format.
system ("$GNUPLOT $gpfile | $PPMTOGIF<\n>
   ." 2> /dev/null > "<\n>
   ."$httproot/$imagedir/$giffile");
unlink ($gpfile, $datafile);

# SECTION 7:
# Output an HTML page to display the graphic we
# just generated.
print "Content-type: text/html\n\n";
print <<EOM;
<HTML>
<BODY bgcolor="#FFFFFF">
<TITLE>Web Access</TITLE>
<h3>Web Accesses</h3>
Total Accesses: <b>$total</b><p>
<IMG SRC=/$imagedir/$giffile><p>
</BODY>
</HTML>
EOM