Perl & Lwp: Fetching Web Pages, Parsing Html, Writing Spiders & More

Perl soared to popularity as a language for creating and managing web content, but with LWP (Library for WWW in Perl), Perl is equally adept at consuming information on the Web. LWP is a suite of modules for fetching and processing web pages.The Web is a vast data source that contains everything from stock prices to movie credits, and with LWP all that data is just a few lines of code away. Anything you do on the Web, whether it's buying or selling, reading or writing, uploading or downloading, news to e-commerce, can be controlled with Perl and LWP. You can automate Web-based purchase orders as easily as you can set up a program to download MP3 files from a web site.Perl & LWP covers:

• Understanding LWP and its design
• Fetching and analyzing URLs
• Extracting information from HTML using regular expressions and tokens
• Working with the structure of HTML documents using trees
• Setting and inspecting HTTP headers and response codes
• Managing cookies
• Accessing information that requires authentication
• Extracting links
• Cooperating with proxy caches
• Writing web spiders (also known as robots) in a safe fashion

Perl & LWP includes many step-by-step examples that show how to apply the various techniques. Programs to extract information from the web sites of BBC News, Altavista, ABEBooks.com, and the Weather Underground, to name just a few, are explained in detail, so that you understand how and why they work.Perl programmers who want to automate and mine the web can pick up this book and be immediately productive. Written by a contributor to LWP, and with a foreword by one of LWP's creators, Perl & LWP is the authoritative guide to this powerful and popular toolkit.

This comprehensive guide to LWP and its applications comes with many practical examples. Topics include fetching Web pages, submitting forms, using various techniques for HTML parsing, handling cookies and authentication.

Perl soared to popularity as a language for creating and managing web content, but with LWP (Library for WWW in Perl), Perl is equally adept at consuming information on the Web. LWP is a suite of modules for fetching and processing web pages.

The Web is a vast data source that contains everything from stock prices to movie credits, and with LWP all that data is just a few lines of code away. Anything you do on the Web, whether it's buying or selling, reading or writing, uploading or downloading, news to e-commerce, can be controlled with Perl and LWP. You can automate Web-based purchase orders as easily as you can set up a program to download MP3 files from a web site.

Perl & LWP covers:

Understanding LWP and its design

Fetching and analyzing URLs

Extracting information from HTML using regular expressions and tokens

Working with the structure of HTML documents using trees

Setting and inspecting HTTP headers and response codes

Managing cookies

Accessing information that requires authentication

Extracting links

Cooperating with proxy caches

Writing web spiders (also known as robots) in a safe fashion

Perl & LWP includes many step-by-step examples that show how to apply the various techniques. Programs to extract information from the web sites of BBC News, Altavista, ABEBooks.com, and the Weather Underground, to name just a few, are explained in detail, so that you understand how and why they work.

Perl programmers who want to automate and mine the web can pick up this book and be immediately productive. Written by a contributor to LWP, and with a foreword by one of LWP's creators, Perl & LWP is the authoritative guide to this powerfuland popular toolkit.

Foreword; Preface; Audience for This Book; Structure of This Book; Order of Chapters; Important Standards Documents; Conventions Used in This Book; Comments and Questions; Acknowledgments; Chapter 1: Introduction to Web Automation; 1.1 The Web as Data Source; 1.2 History of LWP; 1.3 Installing LWP; 1.4 Words of Caution; 1.5 LWP in Action; Chapter 2: Web Basics; 2.1 URLs; 2.2 An HTTP Transaction; 2.3 LWP::Simple; 2.4 Fetching Documents Without LWP::Simple; 2.5 Example: AltaVista; 2.6 HTTP POST; 2.7 Example: Babelfish; Chapter 3: The LWP Class Model; 3.1 The Basic Classes; 3.2 Programming with LWP Classes; 3.3 Inside the do_GET and do_POST Functions; 3.4 User Agents; 3.5 HTTP::Response Objects; 3.6 LWP Classes: Behind the Scenes; Chapter 4: URLs; 4.1 Parsing URLs; 4.2 Relative URLs; 4.3 Converting Absolute URLs to Relative; 4.4 Converting Relative URLs to Absolute; Chapter 5: Forms; 5.1 Elements of an HTML Form; 5.2 LWP and GET Requests; 5.3 Automating Form Analysis; 5.4 Idiosyncrasies of HTML Forms; 5.5 POST Example: License Plates; 5.6 POST Example: ABEBooks.com; 5.7 File Uploads; 5.8 Limits on Forms; Chapter 6: Simple HTML Processing with Regular Expressions; 6.1 Automating Data Extraction; 6.2 Regular Expression Techniques; 6.3 Troubleshooting; 6.4 When Regular Expressions Aren't Enough; 6.5 Example: Extracting Linksfrom a Bookmark File; 6.6 Example: Extracting Linksfrom Arbitrary HTML; 6.7 Example: Extracting Temperatures from Weather Underground; Chapter 7: HTML Processing with Tokens; 7.1 HTML as Tokens; 7.2 Basic HTML::TokeParser Use; 7.3 Individual Tokens; 7.4 Token Sequences; 7.5 More HTML::TokeParser Methods; 7.6 Using Extracted Text; Chapter 8: Tokenizing Walkthrough; 8.1 The Problem; 8.2 Getting the Data; 8.3 Inspecting the HTML; 8.4 First Code; 8.5 Narrowing In; 8.6 Rewrite for Features; 8.7 Alternatives; Chapter 9: HTML Processing with Trees; 9.1 Introduction to Trees; 9.2 HTML::TreeBuilder; 9.3 Processing; 9.4 Example: BBC News; 9.5 Example: Fresh Air; Chapter 10: Modifying HTML with Trees; 10.1 Changing Attributes; 10.2 Deleting Images; 10.3 Detaching and Reattaching; 10.4 Attaching in Another Tree; 10.5 Creating New Elements; Chapter 11: Cookies, Authentication,and Advanced Requests; 11.1 Cookies; 11.2 Adding Extra Request Header Lines; 11.3 Authentication; 11.4 An HTTP Authentication Example:The Unicode Mailing Archive; Chapter 12: Spiders; 12.1 Types of Web-Querying Programs; 12.2 A User Agent for Robots; 12.3 Example: A Link-Checking Spider; 12.4 Ideas for Further Expansion; Appendix A: LWP Modules; Appendix B: HTTP Status Codes; B.1 100s: Informational; B.2 200s: Successful; B.3 300s: Redirection; B.4 400s: Client Errors; B.5 500s: Server Errors; Appendix C: Common MIME Types; Appendix D: Language Tags; Appendix E: Common Content Encodings; Appendix F: ASCII Table; Appendix G: User's View of Object-Oriented Modules; G.1 A User's View of Object-Oriented Modules; G.2 Modules and Their Functional Interfaces; G.3 Modules with Object-Oriented Interfaces; G.4 What Can You Do with Objects?; G.5 What's in an Object?; G.6 What Is an Object Value?; G.7 So Why Do Some Modules Use Objects?; G.8 The Gory Details; Colophon;