404 Error Log

#!/usr/bin/perl
use CGI::Carp qw(fatalsToBrowser);
use CGI qw(:standard);
# 404 error handler
# Michael Roeder
# 5/5/02
# Parameter: ?errorpage=path/to/error.html
#
# Each subdirectory in the web site structure can have its own
# .htaccess file and 404.html file. Each .htaccess file can
# set an ErrorDocument line like this one:
#
#ErrorDocument 404 /cgi-bin/mroeder/404-handler.cgi?errorpage=/404.html
#
# The first part points the server to the 404 handler script.
# The second part points the handler script to the 404 error page.
# If no errorpage is specified in the ErrorDocument line, then
# the default behavior is to serve up the $defaulterrorpage.
# If the errorpage is specified but is missing, this script will
# print an ugly error message.
# If the $defaulterrorpage is needed but is missing, this script
# will likewise print an ugly error message.
#
# Set $logfile to a text file that is to receive the log entries.
# This file needs to be world-writable.
$logfile = '/wwwpages/404-log.txt';
#
# Set $pathprefix the root directory of the web site.
$pathprefix = '/wwwpages';
#
# Set $defaulterrorpage to the error page in that directory.
$defaulterrorpage = '/404.html';
#
# If the log file is missing, print an ugly error message.
# The log file is the whole point of this script.
unless (-e $logfile) {error("$logfile does not exist.")}
unless (-W $logfile) {error("$logfile is not world writable.")}
#
# Build the data for the log file.
#
# get the date and time
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday) = localtime(time);
$mon++;
if (length($mday) == 1) {$mday = 0 . $mday}
if (length($mon) == 1) {$mon = 0 . $mon}
if (length($hour) == 1) {$hour = 0 . $hour}
if (length($min) == 1) {$min = 0 . $min}
$year = $year + 1900;
$dt = "$year$mon$mday.$hour$min";
#
# get the requested URL
$redirect_url = "$ENV{'REDIRECT_URL'}";
#
# Get the URL we were linked from
$http_referrer = "$ENV{'HTTP_REFERER'}";
if ($http_referrer eq "") {
$http_referrer = " ";
}
else {
$http_referrer = "<a href=\"$http_referrer\">$http_referrer</a>"
}
#
# Get the address of the remote web browser.
$remote_address = "$ENV{'REMOTE_ADDR'}";
#
# Get the name of the remote web browser.
$remote_host = "$ENV{'REMOTE_HOST'}";
if ($remote_host eq "") {
$remote_host = "&nbsp;";
# it would be nice if this could do an nslookup and report that
}
#
# Get the type of browser
$user_agent = "$ENV{'HTTP_USER_AGENT'}";
if ($user_agent eq "") {
$user_agent = "&nbsp;";
}
#
# prepare the HTML fragments to make a nice table row.
$entrystart = " <tr>\n <td>";
$delimiter = "</td>\n <td>";
$entryend = "</td>\n </tr>";
#
# build log entry, which is to be one line of table cells
$logentry = $entrystart . $dt . $delimiter . $redirect_url . $delimiter .
$http_referrer . $delimiter . $remote_address . $delimiter .
$remote_host . $delimiter . $user_agent . $entryend ;
#
# write the log entry to the file
open(FILE, ">>$logfile") or error("Could not open $logfile for append: $!");
flock(FILE,2) or error("Could not lock file $logfile: $!");
print FILE $logentry;
close(FILE);
#
# having logged the 404 error, now give the right 404 page
#
# start with the default error page
$errorpage = $pathprefix . $defaulterrorpage;
# get the specified error page parameter
$myerrorpage = param('errorpage');
#
# if something was specified, then set the specified error page
if ($myerrorpage ne '') {
$errorpage = $pathprefix . $myerrorpage;
};
#
# does the error page exist?
unless (-e $errorpage) {
error("$errorpage does not exist.")
};
#
# print the 404-error page to the output
open (FILE,"$errorpage");
$content = '';
while (<FILE>){
$content .= $_;
}
close (FILE);
print "Content-type: text/html\n\n";
print "$content";
# done
exit(0);sub error
{
my $error = $_[0];
print "Content-Type: text/html\n\n";
print "<h2>Error</h2><b>$error</b>\n\n";
exit(0);
}
#eof 404-handler.cgi