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How CGI Scripting Works

        Tech | Programming

The CGI Mechanism

On most Web servers, the CGI mechanism has been standardized in the following way. In the normal directory tree that the server considers to be the root, you create a subdirectory named cgi-bin. (You can see this directory in the figure on the previous page.) The server then understands that any file requested from the special cgi-bin directory should not simply be read and sent, but instead should be executed. The output of the executed program is what it actually sent to the browser that requested the page. The executable is generally either a pure executable, like the output of a C compiler, or it is a PERL script. PERL is an extremely popular language for CGI scripting.

Imagine that you type the following URL into your browser: http://www.howstuffworks.com/cgi-bin/search.pl. The server recognized that search.pl is in the cgi-bin directory, so it executes search.pl (which is a PERL script) and sends the output from the execution to your browser.

You can write your own scripts and try out CGI yourself provided that:

  • You know a programming language such as C or PERL.
  • You have access to a Web server that handles CGI scripts. If you have paid a Web hosting service to host your Web site, then chances are you have access to CGI scripting through your host. Check with the hosting service for details. If not, then you can experiment by installing a Web server on your home machine and learning to use it. The second option is a bit more complicated, but you are guaranteed to learn a lot in the process!