AppleScript: The Definitive Guide, 2nd Edition

CGI Application

A CGI application (for common gateway interface, if you must know) is a process that supplements a web server. When a request arrives for a page, instead of simply fetching a file on disk, the web server can turn to a CGI application and ask it for the page; the CGI application is expected to compose the entire HTML of the page, including headers, and hand it back to the web server, which sends it on as the reply to the client that made the request.

Before Mac OS X, the communication between a web server and a CGI application was conventionally performed on Mac OS through Apple events. In particular, an Apple event usually known (for historical reasons) as the WebSTAR event is sent by the web server to the CGI application, describing the page request. The CGI application hands back the page as the reply to this Apple event (see http://www.4d.com/products/wsdev/internetspecs.html). This means that an AppleScript applet could be used as a CGI application; such, indeed, was the traditional approach. Terminology for the WebSTAR event is defined in the StandardAdditions scripting addition; it is the handle CGI request event. So in the past, you would write an applet implementing an event handler for handle CGI request, and point your web server at that applet as the CGI application for certain web page requests.

With the coming of Mac OS X, however, all this has changed. Of course if you're still using WebSTAR or some other web server that implements CGIs in the traditional ...