MySQL and mSQL

The CGI Specification

So what are the exact “set of rules” that enable a CGI program in say, Batavia, Illinois to communicate with a web browser in Outer Mongolia? The official CGI specification along with lots of other nifty CGI information can be found on NCSA’s web site at http://hoohoo.ncsa.uiuc.edu/cgi/. However, the reason this chapter exists is so that you don’t have to make the long trek to your web browser and look it up yourself.

There are four methods by which CGI passes information between the CGI program and the web server—and hence to the web client:

• Environment variables

• Command line

• Standard input

• Standard output

Using these four methods, the server sends all of the information provided by the client to the CGI program. The CGI program then does its magic and sends the output back to the server where it is forwarded to the client.

Note

This information is written with the Apache HTTP server in mind. Apache is the most widely used web server and is available for virtually all platforms, including Windows 9x and Windows NT. However, this information should also apply to all HTTP servers that support CGI. Some of the more proprietary servers, such as those from Microsoft and Netscape, may have additional features or slightly different operation. As the face of the web is still changing at an incredible speed, standards are still in flux and there will undoubtedly be changes. However, CGI itself seems to have somewhat stabilized—at the expense of being overshadowed by other ...