Webbots, Spiders, and Screen Scrapers: A Guide to Developing Internet Agents with PHP/CURL (Paperback)

by Michael Schrenk (Author)
Key Phrases: insertion parse, login criteria, stealthy webbots, Done Figure, Mozilla Firefox, Bidder's Edge (more...)

Editorial Reviews

Product Description
The Internet is bigger and better than what a mere browser allows. Webbots, Spiders, and Screen Scrapers is for programmers and businesspeople who want to take full advantage of the vast resources available on the Web. There's no reason to let browsers limit your online experience--especially when you can easily automate online tasks to suit your individual needs.

Learn how to write webbots and spiders that do all this and more:

Programmatically download entire websites

Effectively parse data from web pages

Manage cookies

Decode encrypted files

Automate form submissions

Send and receive email

Send SMS alerts to your cell phone

Unlock password-protected websites

Automatically bid in online auctions

Exchange data with FTP and NNTP servers

Sample projects using standard code libraries reinforce these new skills. You'll learn how to create your own webbots and spiders that track online prices, aggregate different data sources into a single web page, and archive the online data you just can't live without. You'll learn inside information from an experienced webbot developer on how and when to write stealthy webbots that mimic human behavior, tips for developing fault-tolerant designs, and various methods for launching and scheduling webbots. You'll also get advice on how to write webbots and spiders that respect website owner property rights, plus techniques for shielding websites from unwanted robots.

Some tasks are just too tedious--or too important!-- to leave to humans. Once you've automated your online life, you'll never let a browser limit the way you use the Internet again.

About the Author

Michael Schrenk develops webbots and spiders for clients across North America. He has written for Computerworld and Web Techniques magazines and has taught college courses on web usability and Internet marketing. He's also an occasional speaker at DEFCON.

Product Details

• Paperback: 328 pages
• Publisher: No Starch Press; annotated edition edition (March 30, 2007)
• Language: English
• ISBN-10: 1593271204
• ISBN-13: 978-1593271206
• Product Dimensions: 9.1 x 6.9 x 0.9 inches
• Shipping Weight: 1.4 pounds (View shipping rates and policies)
• Average Customer Review: 4.6 out of 5 stars See all reviews (14 customer reviews)
• Amazon.com Sales Rank: #65,100 in Books (See Bestsellers in Books)

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Customer Reviews

Most Helpful Customer Reviews

22 of 23 people found the following review helpful:

2.0 out of 5 stars Does the basics., December 5, 2007

By	Brian "eateroftheham" (Crown Point, IN United States) - See all my reviews

"Webbots, Spiders, adn Screen Scrapers" is a solid book for building basic scripts to do web scraping. Michael Schrenk goes covers the "should you do this" aspect very well, and devotes much of the book to these kinds of topics. On that reason alone I give him major kudos, "just because you CAN do a thing, doesn't mean you SHOULD."

Technically the book and examples are very basic and beginner level. All code is procedural and has absolutely no references to object oriented programming at all. This is great for a simple project, but building anything larger than a targetted webbot or two is beyond the scope of this book.

I was very dismayed at Mr. Schrenk's opinion of regular expressions:
"The use of regular expressions is a parsing language in itself, and most modern programming languages support aspects of regular expressions. In the right hands, regular expressions are also useful for parsing and substituting text; however, they are famous for thier sharp learning curve and cryptic syntax. I avoid regular expressions whenever possible."

This disregard for regular expressions effectively wipes out a powerful toolset for budding developers. Regular expressions are no harder to learn than PHP. The reasons for his disdain for them is also flawed:

"The regular expression engine used by PHP is not as efficient as engines used in other languages, and is certainly less efficient than PHP's built-in functions for parsing HTML."

PHP uses the same regular expression engine used (very effectively) in PERL with the use of the preg_* functions. There has been many studies that show preg_* style expressions outperform basic text matching in PHP. In this assesment the author is terribly wrong.

The book does a great job of explaining how to make single use scripts for scraping, but never how to create a larger infrastructure. There is no focus on creating multi process engines with pcntl_fork(), or proc_open(), these are critical for scaling web scraping applications. A single script scraping a few hundred websites on a single thread would take ages over a multi-threaded engine.

If you are looking to break into web scraping and not sure where to start, this is likely the best (and possibly only) book on the market. If you are intermediate or advanced you will quickly question the author's logic and see that scaling will become the number one issue you have to over come.

22 of 24 people found the following review helpful:

3.0 out of 5 stars Solid introduction to webbots, with a catch. , April 27, 2007

By	Paul M. Reinheimer "Author" (Montréal, Quebec, Canada) - See all my reviews (REAL NAME)

I picked up this book full of enthusiasm, spiders are just plain cool, they go out and start downloading data for you, reading webpages, and even understanding them a little. My enthusiasm was dashed a little however on page four: You may use any of the scripts in this book for your own personal use, as long as you agree not to redistribute them... and agree not to sell or create derivative products under any circumstances.. I develop in PHP professionally, and a lot of the code I write ends up getting used somewhere with some sort of a for-profit basis, which pretty effectively prevents me from using any code between the covers (at its strictest reading, Im not sure I can even change the code).

The book does a great job of introducing different sorts of web agents that you can create programatically (more than just spiders) and introduces all sorts of interesting projects along those lines. Throughout the book a series of libraries written by the author are leveraged to make the retrieval and parsing of the various pages much easier. While newer developers will enjoy being able to concentrate on the big picture I found myself itching for more information on the nitty gritty.

Some of the projects explored include: price monitoring, image capturing (want to be your own google image search? :) ), link verification, spiders, and snipers. Each of the different projects received its own chapter, and effectively covered a lot of the topics covered within.

Overall, I would recommend this book to beginner to intermediate PHP developers looking to tackle the world of web agents, its a good primer on the related topics, and at the very least will give you some ideas on the complexities involved. As their skill grows they will probably find them-self either moving past the libraries included with the book, or modifying them greatly. My biggest complaint is the lack of coverage on the robots.txt file, some talk is given to it in terms of blocking robots from your own site, but I didnt see any code that actually dealt with parsing it for your own robot.

15 of 17 people found the following review helpful:

5.0 out of 5 stars WOW, WOW, WOW! I'll say it again...WOW!, April 13, 2007

By	J. Dadlez "Dadio" (Riverside, CA.) - See all my reviews (REAL NAME)

I waited months for this book to come out and the wait was worth it. This is a great introduction to webbots , spiders and scrapers. The writing is easy and never boring. Lots of code examples and resources to tap into. I couldn't put it down. When was the last time you got a computer book that made you run to the keyboard to try something out?

I'm sure there will be some a#$h@#e that will say it's too rudimentory. It's an intro and it takes you up to intermediate and explains stuff about PHP that I didn't even know existed. Definitely worth the money. I can't wait for the sequel.