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"CGI"
stands for "Common Gateway Interface." CGI is the method by which a
web server can obtain data from (or send data to) databases, documents, and other
programs, and present that data to viewers via the web. More simply, CGI is programming
for the web. A CGI can be written in any programming language, but Perl is the
most popular, and for the course of this book, Perl is the language we'll be using. Why
learn CGI?
If you're going to create web pages, then at some point you'll
want to add a counter, a form to let visitors send you mail or place an order,
or something similar. CGI enables you to do that and much more. From mail-forms
and counter programs, to the most complex database scripts that generate entire
websites on-the-fly, CGI programs deliver a broad spectrum of content on the web
today. If you've ever looked at a site such as Amazon.com, DejaNews, or Yahoo,
and wondered how they did it... the answer is CGI. CGI experience is also in high
demand from employers now; you could substantially improve your salary and job
prospects by learning CGI. A CGI program is still a Perl script. Perl is a simple
language, easy to learn, yet powerful enough to accomplish the most difficult
tasks. It is widely available, and is probably already installed on your Unix
server. Perl is an interpreted language, meaning you don't need to compile your
script - you simply write your script and run it (or have the web server run it).
The script itself is just text code; the Perl interpreter does all the work. The
advantage to this is you can copy your script with little or no changes to any
machine with a Perl interpreter. The disadvantage is you won't discover any bugs
in your script until you run it. You can edit your Perl scripts either on your
local machine (using your favorite text editor - Notepad, Simpletext, etc.), or
in the Unix shell.
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