CGI Programming on the World Wide Web By Shishir Gundavaram 1st Edition March 1996 This book is out of print, but it has been made available online through the O'Reilly Open Books Project.

Appendix A

 

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A. Perl CGI Programming FAQ

Contents:
Introduction
Modules
CGI and the WWW Server
Specific Programming Questions
Security

A.1 Introduction

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:

Author	Title	Publisher	Medium	Price
Christian Neuss & Johan Vromans	The Webmaster's Handbook: Perl Power for Your Web Server (http://zelda.thomson.com/itcp/neuss/neuss.html)	Int'l Thomson	CD-ROM	$30
William E. Weinman	The CGI Book	New Riders	CD-ROM	$45
Garbus et al.	Perl Programming Unleashed (March 1996)	Sams.net	CD-ROM	??
Steven E. Brenner & Edwin Aoki	Introduction to CGI & Perl: WebScripts http://www.mispress.com/introcgi /online_app.html)	MIS:Press/M&T Books		??
Ed Tittel et al.	Perl 5 Programming Secrets (March 1996)	IDG Books	CD-ROM	??
Mitzelfelt	Special Edition Using Perl	Que		??
Shishir Gundavaram	CGI Programming on the World Wide Web (http://www.ora.com/gnn/bus/ora/item/cgi_prog.html)	O'Reilly		$30
Rob Farrel	The Official 60 Minute Guide to CGI Programming with Perl (http://db.www.idgbooks.com/database/book/isbn/generic-book.tmpl?query=1-56884-780-7)	IDG Books		$20
Ed Tittel et al.	Web Programming Secrets	IDG Books	CD-ROM	$40
John Deep	Developing CGI Applications with Perl (Dec 1995)	Wiley		$30
Jon Orwant	Perl 5 Interactive (February 1996)	Waite		$30
Reggie David	Perl 5 How-To (Spring 1996)	Waite	CD-ROM	$40
Eric Herrmann	Teach Yourself CGI Programming with Perl in a Week	Sams.net		$30
Walnut Creek CDROM	Perl (Collected resources, archives, tutorial, examples, source code, etc.)	Walnut Creek CDROM	CD-ROM	$40
Carl Dichter & Mark Pease	Software Engineering with Perl (This is an advanced text for software professionals; it is not a tutorial.) (http://www.prenhall.com/013/ 016964/ptr/01696-4.htm)	Prentice Hall	Disk	$30
Ellie Quigley	Perl by Example	Prentice Hall		$27
John December & Mark Ginsburg	HTML & CGI Unleashed	Sams.net	CD-ROM	$50
David Till	Teach Yourself Perl in 21 Days	Sams	Print	$30
Larry Wall & Randal L. Schwartz	Programming Perl	O'Reilly	Print	$30
Randal L. Schwartz	Learning Perl	O'Reilly	Print	$25
Ed Tittel et al.	Foundations of WWW Programming with HTML and CGI	IDG Books	CD-ROM	$40
Eric Lease Morgan	Teaching a New Dog Old Tricks (Mac-based WWW Starter Kit with Server) (http://152.1.24.177/teaching/manuscript/0010-title-page.html)		Online	Free!
Susan B. Peck & Stephen Arrants	WebSite: Everything You Need... (This is a complete Website kit for Windows NT 3.5 or Windows 95) (http://www.ora.com/gnn/bus/ora/item/web11.html)	O'Reilly	CD-ROM	$249
Lincoln D. Stein	How to Set Up and Maintain a World Wide Web Site (http://www-genome.wi.mit.edu/WWW/)	Addison-Wesley		$29
Jonathan Magid et al.	The Web Server Book	Ventana	CD-ROM	$50
net.Genesis & Devra Hall	Build a Web Site	Prima		$35
David Chandler	Running a Perfect Web Site	Que	CD-ROM	$40
Jon Weiderspan & Chuck Shotton	Planning & Managing a Web Site on the Macintosh	Addison-Wesley	CD-ROM	$40

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:

cgi-perl-request@webstorm.com [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 (Tim.Bunce@ig.co.uk) wrote several elegant and useful CGI modules, although they are currently maintained by Lincoln Stein (lstein@genome.wi.mit.edu). 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).

libwww-perlrequest@ics.uci.edu [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.

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