Historical Context of CGI

In 1993, the standard for invoking command line executables was written by the National Center for Supercomputing Applications (NCSA) team and posted to the www-talk mailing list. It was embraced by the other Web server creators, and ever since then, Web servers have used it as a standard. A work group headed by Ken Coar was established in November 1997 to formalize the NCSA definition of CGI. This effort led to the creation of RFC 3875, which described CGI Version 1.1. Specifically mentioned in the RFC are the following contributors:

• Rob McCool, the author of the NCSA HTTPd Web server
• John Franks, the author of the GN Web server
• Ari Luotonen, the developer of the CERN httpd Web server
• Tony Sanders, the author of the Plexus Web server
• George Phillips, the Web server maintainer at the University of British Columbia

In ancient times, C programming language was popularly used for creating CGI apps. RFC 3875 “The Common Gateway Interface (CGI)” has partially defined CGI using C, in saying that environment variables “are accessed by the C library routine getenv() or variable environ”.

When webmasters first started using the Web and wished to link existing information systems, such as databases, to their Web servers, they gave the technology the term CGI. The server that served as a common “gateway” between the Web server and the older information system, ran the CGI application.

When you click on any of the links on the webpage, your browser contacts the HTTP web server and demands the URL that is, the filename, and the web server passes the URL and looks for the filename, if it finds that file, it will send it back to the browser otherwise sends an indicating message that you have requested a wrong file. Then, the web browser takes a response from the web server and displays either the received file or the error message. However, it is possible to set the HTTP server so that whenever a file in a certain directory is requested, that file is not sent back. Instead, it is executed as a program. And, whenever that program shows any output, it’s sent back to the browser to display. So, this function is called Common Gateway Interface or CGI, and the program scripts are called CGI Scripts. These CGI scripts can be a Python script, PERL script, Shell script, C or C++ program, etc.