Why does my HTML page/form need a script?

There are times when you might want to have some dynamic information (information that is not constant) in your HTML documents. This could include simple information such as the date and time, or a counter that displays "You are visitor number xxx", but it could also include such things as pie charts/graphs based on user input, results from searching a database, or animations. And the only way you can produce results like these is with CGI scripts (though you can also do so with client-side applications like Java and JavaScript, but that's a totally different story!).

What does CGI stand for?

Here is an excellent description that my editor, Andy Oram, wrote up:

Common

Assures you that CGI can be used by many languages and interact with many different types of systems. It doesn't tie you down to one way of doing what you want.

Gateway

Suggests that CGI's strength lies not in what it does by itself, but in the potential access it offers to other systems such as databases and graphic generators.

Interface

Means that CGI provides a well-defined way to call up its features--in other words, that you can write programs that use it.

What is a script, anyway? What can I do with a script?

Simply put, a script is a program! OK, OK, there are semantic differences between the two words. If you really want to know, pick up a book on computer programming (or is that computer scripting :-)

You can create a lot of magic by writing a CGI program/script. You can create graphics on the fly, access databases and return results, and connect to other Internet information servers.

What is Perl and why do so many people use it for CGI?

The answer is located in the first three lines of the Perl manpage:

Perl is an interpreted language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information.

Most CGI applications involve manipulating data in some fashion and accessing external programs and applications. Perl provides easy-to-use tools that make these tasks a cinch.

Is there a book or online docs on CGI and/or Perl programming?

Here is a list of books on CGI and Perl. I got this list from Cye H. Waldman:

• NCSA CGI Documentation (http://hoohoo.ncsa.uiuc.edu/cgi)

• Forms Tutorial (http://robot0.ge.uiuc.edu/~carlosp/cs317/ft.4-5.html)

• CGI FAQ (http://www.best.com/~hedlund/cgi-faq

• Perl FAQ (<http://mox.perl.com/perl/faq/index.html)

• WWW Security FAQ (by Lincoln Stein) (http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html)

• CGI Security FAQ (by Paul Phillips) (http://www.cerf.net/~paulp/cgi-security/safe-cgi.txt)

• WWW FAQ (http://boutell.com/faq)

Here is a table of books and CD-ROMS about CGI and Perl:

Is there a mailing list or newsgroup for this kind of thing?

There is a very useful newsgroup: comp.infosystems.www.authoring.cgi, that is "monitored" by numerous CGI experts. However, you should not post a question to this group (or any other group, for that matter), until you have read the FAQ.

Various mailing lists for CGI and the Web exist, as well. Here are two of the most popular:

[email protected] [http://www.webstorm.com/local/cgi-perl]

This list is for those who are writing or interested in writing Perl 5 modules for CGI. It is not intended for any type of CGI support.

Tim Bunce ([email protected]) wrote several elegant and useful CGI modules, although they are currently maintained by Lincoln Stein ([email protected]). These modules are located at:

http://www-genome.wi.mit.edu/WWW/tools/scripting/CGIperl

Lincoln has also written an excellent book on the Web and CGI (see the preceding table).

[email protected] [http://www.ics.uci.edu/WebSoft/libwww-perl/archive]

libwww-perl is a Perl library that provides a simple and consistent programming interface to the Web.

You can access the Perl 4 distribution at:

http://www.ics.uci.edu/pub/websoft/libwww-perl

The Perl 5 libwww modules are located at:

http://www.os/oslonett.no/home/aas/perl/www

Are there archives on the net of mailings or postings about this?

Yes, look at:

The Usenet Newstand (http://CriticalMass.com/Concord/)

All of the comp.infosystems.www.* newsgroups are archived. In addition, the cgi-perl and libwww mailing lists are archived as well.