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Michael Schrenk uses webbots and data-driven web applications to create competitive advantages for businesses. He has written for Computerworld and Web Techniques magazines and has taught courses on Web usability and Internet marketing. He has also given presentations on intelligent Web agents and online corporate intelligence at the DEFCON hacker's convention.
"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.Read more ›
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, I’m 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 it’s 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, it’s a good primer on the related topics, and at the very least will give you some ideas on the complexities involved.Read more ›
This book covers every aspect I could ever hope a book on web bots would cover. It goes into great detail and provides lots of background information about things such as why you should use web bots, security issues, how to authenticate a bot with password protected sites, writing search engine crawlers, parsing HTML, how to handle cookies, HTTP headers, dealing with forms and a lot more.
I was very pleased with how this book covered concepts. The book uses PHP and the cURL library as a teaching tool instead of trying to give a lesson in how to use PHP as a crawler language. The way the code is explained makes it very easy to translate into whatever language you are most comfortable coding in. The book uses fundamental functional programming concepts which make it easy to pick up the general idea without actually knowing PHP.
My boss bought this book to help my group us with a project we were working on, and even my co-workers who had no background with PHP were able to use this book to write a web bot in C# (using the cURL library) very easily. The concepts from this book easily transfered over to object-oriented concepts.
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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.
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Michael Schrenk is a software developer, author and instructor. He specializes in automated web browsing agents known as webbots. His book, "Webbots, Spiders, & Screen Scrapers" (2007, No Starch Press, San Francisco) is the definitive work on the subject.
Michael uses the Internet in new and innovative (odd?) ways to provide competitive advantages for his clients in The US, Europe and Asia.
He also helps journalists more effectively use computers to conduct online research through automation and by describing where and how to find otherwise hidden online information. No stranger to Europe--he's lived in Moscow and Madrid, Mike taught at the 2008 European Investigative Journalism Conference (Brussels Belgium), twice in 2009 he lectured at The Center for Investigative Journalism (London England) and later in 2009, he lead several sessions at the VVOJ Journalism conference (Utrecht The Netherlands).
Last August, Mike made his fourth speaking appearance at the DEFCON computer hacking conference. Mike lives in sunny Las Vegas, Nevada (USA). You can contact him at http://www.schrenk.com
Watch this book's video at: http://www.youtube.com/watch?v=B7z7tP74RxQ