if statement based on HTTP_REFERER

[Jesse Smith]

Is it possible to have two different logs generated, and the one that get's data added when the script is loaded depends on if there is a HTTP_REFERER?

if (  THERE IS A $ENV{'HTTP_REFERER'}  ) {
$shortdate = `date +"%D %T %Z"`; 
chop ($shortdate);
    open (DATABASE,">>$database");
        print DATABASE "$ENV{'REMOTE_ADDR'} - $shortdate - $ENV{'HTTP_
+USER_AGENT'} - <A HREF=\"http://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}\
+">http://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}</a> - <A HREF=\"$ENV{'H
+TTP_REFERER'}\">$ENV{'HTTP_REFERER'}</a>\n";
    close(DATABASE);
}
else{
$shortdate = `date +"%D %T %Z"`; 
chop ($shortdate);
    open (DATABASE2,">>$DATABASE2");
        print DATABASE2 "$ENV{'REMOTE_ADDR'} - $shortdate - $ENV{'HTTP
+_USER_AGENT'} - <A HREF=\"http://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}
+\">http://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}</a> - NO HTTP_REFERER\
+n";
    close(DATABASE2);
}

[Perlbotics]

Yes, it's possible.
You will most probably need some kind of locking (see flock) in order to avoid, that simultaneous invocations do interfere. Have a look at a logging framework like i.e. Log::Log4perl. It will allow you to have diffent loggers, log-rotation, locking etc.

Update: You also need to check for empty/undefined HTTP_REFERER.

[MidLifeXis]

Be aware (if it matters) that the REFERRER value is set by the client, and is therefore not to be trusted. In other words, it can be spoofed.

[Athanasius]

Hello Jesse Smith,

Another point: Please note that it is both simpler and safer to avoid code duplication whenever possible:

my $db_name = $DATABASE2;
my $suffix  = 'NO HTTP_REFERRER';

if (defined $ENV{'HTTP_REFERRER'} &&
    length  $ENV{'HTTP_REFERRER'} > 0)
{
   $db_name = $database;
   $suffix  = "<A HREF=\"$ENV{'HTTP_REFERRER'}\">$ENV{'HTTP_REFERRER'}
+</a>";
}

$shortdate = `date +"%D %T %Z"`; 
chomp $shortdate;

open(my $db, '>>', $db_name) or die "Cannot open database '$db_name' f
+or appending: $!";

print $db "$ENV{'REMOTE_ADDR'} - $shortdate - $ENV{'HTTP_USER_AGENT'} 
+- " .
          "<A HREF=\"http://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}\">htt
+p://$ENV{'HTTP_HOST'}$ENV{'REQUEST_URI'}</a> - $suffix\n";

close($db) or die "Cannot close database '$db_name': $!";

(Code untested, and with suggested improvements included: chomp instead of chop, the 3-argument form of open, a lexical filehandle, and testing for file open and close errors.)

Hope that helps,