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Writing CGI Applications with Perl

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Writing CGI Applications with Perl


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  • Copyright 2001
  • Dimensions: 7-3/8x9-1/4
  • Pages: 560
  • Edition: 1st
  • Book
  • ISBN-10: 0-201-71014-5
  • ISBN-13: 978-0-201-71014-4

Writing CGI Applications with Perl offers the most practical examples of applying Web programming techniques to real world problems I've seen yet. The text blends good CGI programming techniques, idiomatic Perl, and databases into many large and useful examples. Careful attention is paid to demonstrating solid, scalable code for production use. This is not your typical 'Hello, World' CGI programming book.
--Clinton Pierce, Perl trainer and author of Teach Yourself Perl in 24 Hours

With its sophisticated database, network, and multi-platform capabilities, the Perl programming language has emerged as an ideal tool for developing CGI-based Web applications.

Writing CGI Applications with Perl shows you how to use Perl to accomplish the most vital tasks needed for today's online applications. Using numerous examples, line-by-line code explanations, and skill-stretching exercises, this book not only provides useful cut-and-paste code for your own programs, but it also teaches you practical skills and techniques that will enable you to develop any kind of CGI-based Web application with Perl.

Focusing on the most important areas of Web application development, including database interaction, form and file handling, security, e-mail, and graphics, the book provides in-depth coverage of such specific topics as:

  • Working with HTML Web forms and obtaining user input
  • Cookies, tracking clicks, and access counters
  • Using the mod_perl Apache module
  • Connecting to a POP3 server for e-mail
  • Perl DBI and databases on the Web
  • Tying a hash to a database
  • Embedding Perl in HTML with HTML::Mason
  • Remote file management via the Web
  • Creating dynamic images
  • XML and its derivatives, RSS and RDF

In addition, introductory material is provided for newcomers to CGI or Perl. Numerous appendices include handy references as well as a guide to Perl documentation. A companion Web site, http://www.perlcgi-book.com, contains the code for all the examples.

Geared toward the needs of today's professional Web developers, Writing CGI Applications with Perl provides the specific tools, experienced-based techniques, and overall concepts necessary for quality Web application development.



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Table of Contents




1. Perl, CGI, and this Book.

What Is Perl?

What Is CGI?

Why Perl Is Good for CGI.

About this Book.

Who Is this Book For?

Conventions Used in this Book.

Using perldoc.

Using the CPAN.

2. What You Should Know.



File Permissions.

Basic Security Concerns.

Using -T.

Checking for Taintedness and Laundering Data.

Your PATH and -T.

Installing a Script.



The Expires HTTP Header.

Cache-Control HTTP Header.


3. Using Your Environment.

Introduction to %ENV.

Adding to %ENV.

Form Input Primer.

Example Script: Visitor Log.

Example Script: Basic Report.

Reader Exercise.

What Have We Learned?


4. Introduction to Web Forms.


Form Tags.

Reading Form Input with CGI.pm.

Making Your Users Happy.

Final Example.

User Exercises.

Program Listings.

5. Working with Cookies.




Cookie Pieces.

Working with Cookies the Manual Way.

Baking Cookies with CGI.pm.

Controlling User Preferences with Cookies.

User Exercises.

6. Access Counters.


Example Script: SSI Text Counter.

Example Script: SSI Image Counter.

Example Script: SSI Text Counter, with a Twist.

Example Script: An Imageless Image Counter.

Counter Conclusion.

Reader Exercises.


7. Web-Based File Uploading.


File Uploading Basics.

Viewing Files.

Uploading Multiple Files.

Reader Exercises.

File Listings.

8. Tracking Clicks.


Example Script: A Simple Click Tracker.

Example Script: Random Images.

Example Script: Click Tracking (Reprise).

Reader Exercises.


9. Using mod_perl.

What Is mod_perl?

Configuring mod_perl.


Automatic Headers and Footers with Apache::Sandwich.

A mod_perl Photo Album with Apache::Album.

Authentication with Apache::AuthDBI.

Writing a mod_perl Handler.

Reader Exercises.


10. Web-Based E-mail.


Example Script: Checking POP3 Mail via the Web.

Example Script: Reading E-mail via the Web.

Example Script: Displaying Attachments.

Example Script: Composing E-mail.

Reader Exercises.


11. Introduction to DBI and Databases on the Web.


Using the Perl DBI.

Connecting to the Database.

Disconnecting from the Database.

Preparing and Executing an SQL Query.

Fetching Data.

The fetchall_arrayref( ) Method.

The fetchrow_arrayref( ) Method.

The fetchrow_hashref( ) Method.

The bind_columns( ) Method.

Putting It All Together.

The do( ) Method.

Wrapping It Up.

Reader Exercises.


12. Tied Variables.


Setting It All Up.

Getting Started.

Diving In.

The Main Program.

Finishing the ShopCart Module.

Running the Program.

Wrapping It Up.

Program Listings.

13. Embedding Perl in HTML with Mason.



The Strategy.

Mason Syntax.

Special Mason Components.

Cascading Execution.

Moving Right Along.




Wrapping It Up: The Code for the Example Site.

14. Document Management via the Web.


The Plan.






Program Listings.

15. Dynamically Manipulating Images.


Adding Shapes and Text.

Creating a Dynamic Graph.

Creating Thumbnail Images.

Filtering Images with Image::Magick.

Animated Images.

Reader Exercises.


16. RSS And XML.

XML and RSS Overview.

Structure of an XML Document.

News Portals with RSS.

A Home Page News Portal.

Creating an RSS File.

Reader Exercises.


Appendix A. Server Codes.

Provide confirmation that a request is being processed.

Request was performed.

Request not performed.

Request is incomplete.

Internal server errors.

Appendix B. Environment Variables.

Appendix C. POSIX::strftime( ) Formats.

Appendix D. General Public License.

Appendix E. Artistic License.

Appendix F. Perl Documentation.

Appendix G. ASCII Codes.

Appendix H. Special HTML Characters.


Index. 0201710145T04062001


Purpose of this Book

Perl's popularity as a CGI scripting language is growing by leaps and bounds. However, there are few books available today that cover this subject in depth including a broad range of concepts. We wanted our book to help people learn to use Perl and convince them that it is the best choice for their Web-based applications. The goal of this book is not to teach the Perl language--although certain tricks and features may be learned--but to show how Perl can accomplish the tasks needed for many of today's online applications. In short, we wanted to provide a resource that not only teaches new uses of Perl but challenges the reader with exercises that use the concepts. Standard Perl documentation is also provided. The book covers a wide range of concepts, and using these, you should be able to write almost any Perl/CGI application with the techniques provided.

This book is different from others about Perl and CGI. It takes a cumulative approach and introduces applications that use concepts learned in previous chapters. Each chapter will cover at least one specific Web-based application and explain the code line by line (or block by block) so you not only learn what the scripts are doing but how they are doing it. And in order to help induce self-learning and application building, each application is working but incomplete. We provide skeleton applications that can stand on their own, but we leave out certain features that can be added (and we suggest adding them in the exercises) using the information in that chapter and in previous chapters. Our goal is not to give you "cut and paste" software but rather to show you how to write the software yourself.

Chapter Summaries

Chapter 1, Perl, CGI, and this Book. This chapter explains what Perl and CGI are. It also supplies more detail about this book and shows how to use the CPAN module.

Chapter 2, What You Should Know. We don't expect the reader to know everything, but we do expect at least a base level of knowledge. This chapter outlines what you should already know and explains a few things that you may not already know but should to get the most out of this book, such as tainting, security concerns, and troubleshooting.

Chapter 3, Using Your Environment. Many times in CGI applications you need information from the client, such as IP address or browser information. This chapter covers how to access the Web server environment variables and what they mean.

Chapter 4, Introduction to Web Forms. There are few online applications where there is not some sort of Web form used to allow an end user to submit information. Chapter 4 explains the HTML elements of creating a Web form, as well as how to obtain the user input.

Chapter 5, Working with Cookies. Using cookies to store data on a Web client can be very useful to record the preferences of and remember things about users. You will learn how to set, get, and use cookies in this chapter.

Chapter 6, Access Counters. Many people want to count how many people come to their Web site. The examples in this chapter show you how to do this.

Chapter 7, Web-Based File Uploading. Here you will learn how to safely allow end users to upload files to a server from their local hard drives.

Chapter 8, Tracking Clicks. It can sometimes be useful to know what links on a Web site are being followed and from where. The examples in this chapter show how to track these clicks.

Chapter 9, Using mod_perl. The popular mod_perl Apache module can be extremely useful when it is appropriate for an application. You will see how to configure mod_perl, as well as how to use and write mod_perl Perl modules.

Chapter 10, Web-Based E-mail. The examples in this chapter demonstrate how to connect to a POP3 server to view e-mail, view attachments, and send e-mail via the Web.

Chapter 11, Introduction to DBI and Databases on the Web. Chapters 1–10 presented basic uses for database connectivity in previous examples. This chapter examines the Perl DBI in more depth.

Chapter 12, Tied Variables. The magic of tying data structures to variables and how to do this when the data structure is a database is explained in this chapter.

Chapter 13, Embedding Perl in HTML with Mason. This popular tool is examined and explained. This chapter shows you how to embed Perl within HTML and use the HTML::Mason module to speed up development and maintenance time.

Chapter 14, Document Management via the Web. By now you will have learned how to upload files to a server. This chapter shows you how to manage your files remotely via the Web.

Chapter 15, Dynamically Manipulating Images. Creating charts, graphs, thumbnails, and galleries, and changing images on the fly are all concepts that can be useful in CGI applications. This chapter shows you how to add these techniques to your software.

Chapter 16, RSS and XML. XML is another tool that is gaining in use and popularity. This chapter shows you how to use both XML and a derivative of it, RSS and RDF, to share information and use in applications.

Appendix A, Server Codes. Learn what the codes returned by a Web server mean.

Appendix B, Environment Variables. This is a list of the most common Web server environment variables.

Appendix C, POSIX::strftime() Formats. This book uses the POSIX module a few times to format date strings. This list shows the formats that the module uses and what the formats do.

Appendix D, General Public License. If you didn't read the copy that came with Perl, you can do so here.

Appendix E, Artistic License. Another license under which Perl is distributed.

Appendix F, Perl Documentation. A list of the documentation that comes with Perl. This list is useful for interactive learning along with this book.

Appendix G, ASCII Codes. A list of ASCII, hex, and decimal codes.

Appendix H, Special HTML Characters. A list of special characters, such as £, ®, and Æ. Although these aren't specific to Perl, you will probably need some of them sooner or later when generating HTML with Perl.

Other Resources

One of the best resources for Perl is the Perl documentation and the documentation included in various Perl modules. Chapter 1 covers how to read this documentation with the perldoc command. The Perl homepage at http://www.perl.com is extremely useful with articles, tips, documentation, other resource links, and what's new in the world of Perl. The Perl Mongers homepage at http://www.perl.org supplies good information on the world of Perl and Perl advocacy. The use Perl Web site at http://use.perl.org is a community page where Perl information is shared and discussed. The Perl Documentation Web site at http://www.perldoc.com is a very useful site containing the latest Perl documentation. Finally, the Perl Monks at http://www.perlmonks.com is another community where people can ask questions, answer questions, chat, and share knowledge.

Usenet has Perl newsgroups that are also useful: comp.lang.perl.announce has Perl announcements; comp.lang.perl.misc is a high traffic list for asking Perl-related questions; and comp.lang.perl.modules announces and discusses Perl modules. A non-Perl-specific news group that deals with CGI is comp.infosystems.www.authoring.cgi. Here you can discuss all topics CGI.

Contacting Us

We would love to hear from you. You can find information on this book and errata at http://www.perlcgi-book.com and http://www.awl.com



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