i n t e r n e t c o n s u l t a n t s

Redirect List Tutorial

This tutorial shows you how a simple CGI program creates a nifty way to let visitors jump to any area of your website. I'll even show you how to speed things up with a snippet of JAVA. You need to have access to a common program called "redirect.pl" in your webserver's cgi-bin, or the ability to add the program.

Redirect Lists in Action

The first example shows a redirect list that allows you to select a destination and press "Submit" to jump to that URL. The second list uses an image instead of a submit button. The third example adds a line of JAVA that causes the browser to immediately jump to the selected URL.

HTML Code for Redirect Lists

<form method="POST" action="/cgi/redirect.pl">
<select name="url">
<option value=""> Select a Page to Visit
<option value=""http://url.one/"> URL One
<option value="http://url.two/"> URL Two
<option value="http://url.three/"> URL Three
</select>
<input type=submit name=submit value="Submit">
</form>

The first line of the HTML code will probably work for your server, but if you don't keep your executable files in /cgi/ it might need to be changed to indicate the correct directory. The "Submit" button can be labelled with any value you please. To use an image instead of a submit button, substitute the following "input" line:

<input type=image border=0 src="image.gif">

JAVA-based automatic redirection, shown below, only works on JAVA-enabled browsers, which include 72% of the market based on our August 1998 log files. To make the redirection automatic for JAVA-enabled browsers, substitute the following "select" line:

<select name="url" onChange="submit(); return true">

The Perl Script

You might already have access to a redirect.pl script. Try the HTML code above and see if it works! If not, you will need to copy the Perl script below to a file called "redirect.pl" in your cgi-bin (or whatever you call it -- mine is just "cgi"). Change the permissions (chmod 755 redirect.pl) and edit the first line of redirect.pl to reflect the location of Perl on your server.

#!/usr/bin/perl
# NOTE: Modify the first line to point to the local Perl program.
# 
# redirect.pl
#
read(STDIN, $query_string, $ENV{'CONTENT_LENGTH'});
# Parse name-value pairs and de-webbify.
@key_value_pairs = split(/&/, $query_string);
foreach $key_value (@key_value_pairs) {
 ($key, $value) = split (/=/, $key_value);
 $key =~ tr/+/ /;
 $value =~ tr/+/ /;
 $value =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack ("C", hex($1))/eg;
 if (defined($array{$key})) {
 $array{$key} = join("|", $array{$key}, $value);
 } else {
 $array{$key} = $value;
 }
} 
if ($array{'url'} eq "") {
 print "Status: 204 Do Nothing\n\n";
 exit(0);
}
elsif ($array{'url'} !~ /^http/) {
 $prefix = "http://" . $ENV{'SERVER_NAME'};
 if ($ENV{'SERVER_PORT'} ne "80") {
 $prefix .= ":" . $ENV{'SERVER_PORT'};
 }
 if ($array{'url'} !~ /^\//) {
 $prefix .= "/";
 }
 $array{'url'} = $prefix . $array{'url'};
}
print <<EOF;
Content-type: text/html
Location: $array{'url'}

EOF

This Redirection List Tutorial is just one example of the expertise of our staff. Want to learn more? Contact us for more information!

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