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Occasionally you may wish to insert a visitor's IP address or other tracking information into a web page for the visitor to see. For example, on sweepstakes or other pages that might attract those with a predisposition to fraud, you might want to say, "Your IP Address ______ is being logged." Your page will have placeholders where the custom information is to be inserted. For example, where you want the visitor's IP address inserted, put: [[REMOTE_ADDR]] Other information available for insertion is listed below. The way it works is that a CGI script retrieves your page, replaces your placeholders with the actual information, and sends the modified page to the visitor's browser. The Script Here is the ten-line script that does the work:
#!/usr/bin/perl
my $Default = 'http://domain.com/page.html';
use LWP::Simple;
my $URL = $ENV{QUERY_STRING};
$URL = $Default unless $URL =~ m!^https?://.+!i;
my $Page = get $URL;
$Page = qq(URL "$URL" not available.) unless $Page;
for(keys %ENV) { $Page =~ s/\[\[$_\]\]/$ENV{$_}/sig; }
$Page =~ s/\[\[.*?\]\]//sg;
print "Content-Type: text/html\n\n$Page";
The first line is the location of Perl on your server. Edit the line if needed. The second line contains the URL of the page the script will display if no other URL has been specified. Edit the URL. The third line loads the Perl module LWP::Simple. This module lets the script retrieve pages from the internet. Line four grabs the URL specified when the script's link was clicked on (see "The Script Link," below). If no URL was specified or if the URL did not begin with "http://" or "https://" then the default URL is assumed on line five. Line six retrieves the page from the internet. If it is a 404 or some other reason prevents the page from being retrieved, line seven provides default text. You may edit the default text between the parenthesis, if you wish. Line eight replaces your placeholders with custom information. Line nine strips any placeholders that might be left in the page when the information was not available. And line ten sends the page to the browser. Edit the script with an ASCII/plain text word processor and save it as insert.cgi or whatever other name makes sense to you. Upload it to your server as ASCII/plain text and set global execution permissions (0755). The Script Link The link to the script is its URL: <a href="http://domain.com/cgi-bin/insert.cgi"> click here </a> If you want to display a page other than the one at the default URL, add a question mark to the above URL followed by the URL of the page you want to display. The link URL would be like this: http://domain.com/cgi-bin/insert.cgi?http://domain.com/page.html Preparing the Page The page that will be displayed with insert.cgi might need a bit of special preparation. If the page has images, each scr="______" must be a complete http://... URL. Same with sound, form action="____", and the URLs of external style sheet and JavaScript files. In other words, every URL on the page must be a complete http://... URL. That's because the page will be displayed from within insert.cgi -- the script is likely to be in a different directory than the page being displayed, so relative URLs will not work. There is an exception to the "every URL" rule: Server Side Includes will work without modification. That's because SSI commands are completed before insert.cgi receives the page. Information Available for Insertion Different servers can provide different information for your pages. Some servers have a lot of data available for your use. Use Master Pre-Installation Tester from http://willmaster.com/a/9/pl.pl?pit and select "Report environment variables" to see a complete list for your server. Some information is available on most servers. Here are three:
This code Is replaced with
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[[REMOTE_ADDR]] The visitor's IP address.
[[HTTP_REFERER]] The referring URL (if available).
[[HTTP_USER_AGENT]] A cryptic synopsis of the visitor's
operating system and browser types.
Note that the referring URL is not available unless the visitor arrives at insert.cgi by clicking on a link on a web page. Further, some browsers can turn off tracking information which tends to eliminate referrer information that would otherwise be available. Demonstration A demonstration page is at http://willmaster.com/a/9/pl.pl?95art If you can't use this now, you might in the future. Most of all, have fun with it! Copyright 2001 William Bontrager
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