#!/usr/bin/perl

use Fcntl ':flock';
use MIME::Base64;
use CGI qw(header);

my $file = "/home/master/webroot/perlskripts/ip.log";

if ( open(my $fh, '>>', $file) ) {
  # lock the file
  flock($fh,LOCK_EX);

  # seek to the end in case someone altered 
  # the file since we opened it
  seek($fh, 0, 2);

  # add the entry to the file
  print $fh "User from ".$ENV{'REMOTE_ADDR'}." logged on\n";

  # unlock
  flock($fh,LOCK_UN);
} else {
  print STDERR "Could not open file for append: $!\n";
}

# always send a clear gif to the browser
my $q = CGI->new();
$q->header(-type => 'image/gif');

# The following is a base64 encoded 1x1 clear gif image
print MIME::Base64::decode_base64('R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==');