Writing Apache Modules with Perl and C

1.1. Web Programming Then and Now

In the beginning was the web server. Specifically, in the very very beginning was CERN httpd , a C-language server developed at CERN, the European high-energy physics lab, by Tim Berners-Lee, Ari Luotonen, and Henrik Frystyk Nielsen around 1991. CERN httpd was designed to serve static web pages. The server listened to the network for Uniform Resource Locator (URL) requests using what would eventually be called the HTTP/0.9 protocol, translated the URLs into file paths, and returned the contents of the files to the waiting client. If you wanted to extend the functionality of the web server—for example, to hook it up to a bibliographic database of scientific papers—you had to modify the server's source code and recompile.

This was neither very flexible nor very easy to do. So early on, CERN httpd was enhanced to launch external programs to handle certain URL requests. Special URLs, recognized with a complex system of pattern matching and string transformation rules, would invoke a command shell to run an external script or program. The output of the script would then be redirected to the browser, generating a web page on the fly. A simple scheme allowed users to pass argument lists to the script, allowing developers to create keyword search systems and other basic applications.

Meanwhile, Rob McCool, of the National Center for Supercomputing Applications at the University of Illinois, was developing another web server to accompany NCSA's browser ...