CGI (Common Gateway Interface) has allowed the web to become much more interactive than it ever was. Instead of a text file being displayed once you call for it from the server, the output of a small program (or script) is displayed in its place on the browser. Text files do not change and are called static. However, a CGI script is an executable program that outputs dynamic, or unchanging, information.

Because scripts generate upon demand, they are capable of incorporating information which changes or which cannot be determined in advance. This allows the CGI script to be used as an interpreter of  user-supplied data (i.e. comment forms), retrieve requested information, or produce content which has been customized for a particular user. With CGI scripts, you can create sound and pictures, as well as HTML documents for your viewers.

To create one of these CGI programs (scripts) you have to learn how to write it and a little about the language you must write it in. One of the easiest "scripting languages" to learn is Perl. Unlike "programming languages" (i.e. C, C++, Fortran), you will not need to compile the CGI program. It is easier to edit or modify, debug, and maintain, and simply sits in the / cgi-bin directory that your WebMaster assigns for it. If you are an alumni member, faculty, staff, or student, you can request space in the campus CGI Bin.

Introduction & Tutorials

• Web Engineer's Toolbox: CGI Programming 101
  An amazing teaching tool, lesson by lesson! Don't skip this informative guide that will instruct you from the ground up!
• Instantaneous Introduction to CGI Scripts and HTML Forms
  The University of Kansas has illustrated the working relationship of CGI scripts and HTML forms with diagrams and great examples. This invaluable resource is for everyone and is really easy to read.
• CGI Scripting by Example
  This is a great site that takes you step by step with easy to follow examples and an ends with a check list to get you familiarized with CGI troubleshooting.

CGI Security & Troubleshooting

• How to debug CGI Scripts
  Common causes why your scripts might not work and how to debug them so they will.
• Idiot's Guide to Solving Perl/CGI Problems
  An excellent list of things to watch for when writing CGI programs. Ask yourself the questions this list poses, and your likely to solve your CGI problems quickly.
• CGI Security Tutorial
  These tutorials focus on defensive programming techniques that will prevent the abuse of CGI scripts.

Script Archives

• Matt's Script Archive
  One of the oldest and most populous CGI script archive sites. Contains many free (for con-commercial use) Perl scripts and modifications.
• Selena Sol's Script Archive 
  Another good source for CGI scripts. Useful scripts written in Perl, along with a good FAQ section, and an excellent resource list.

More CGI Resources

• The Common Gateway Interface (CGI) Specs
  The original CGI specifications documentation. A bit heady, but a good resource to fall back on.
• Books on Perl and CGI
  An extensive list of titles and prices of instructional books.
• O'Reilly Books
  Learn at your own pace! Visit the site of one of the most respected computer publications companies for information on books addressing various Web topics.
• Search Yahoo or Altavista for more information on "CGI"