Webbots, Spiders, and Screen Scrapers - Michael Schrenk [5]
About the Website
This book's website (http://www.schrenk.com/nostarch/webbots) is an additional resource for you to use. To the extent that it's possible, all the example projects in this book use web pages on the companion site as targets, or resources for your webbots to download and take action on. These targets provided a consistent (unchanging) environment for you to hone your webbot writing skills. A controlled learning environment is important because, regardless of our best efforts, webbots can fail when their target websites change. Knowing that your targets are unchanging makes the task of debugging a little easier.
The companion website also has links to other sites of interest, white papers, book updates, and an area where you can communicate with other webbot developers (see Figure 2). From the website, you will also be able to access all of the example code libraries used in this book.
Figure 2. The official website of Webbots, Spiders, and Screen Scrapers
About the Code
Most of the scripts in this book are straight PHP. However, sometimes PHP and HTML are intermixed in the same script—and in many cases, on the same line. In those situations, a bold typeface differentiates PHP scripts from HTML, as shown in Listing 1.
You may use any of the scripts in this book for your own personal use, as long as you agree not to redistribute them. If you use any script in this book, you also consent to bear full responsibility for its use and execution and agree not to sell or create derivative products, under any circumstances. However, if you do improve any of these scripts or develop entirely new (related) scripts, you are encouraged to share them with the webbot community via the book's website.
Coding Conventions for Embedded PHP
| Name | Address |
|---|---|
Listing 1-1: Bold typeface differentiates PHP from HTML script
The other thing you should know about the example scripts is that they are teaching aids. The scripts may not reflect the most efficient programming method, because their primary goal is readability.
Note
The code libraries used by this book are governed by the W3C Software Notice and License (http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231) and are available for download from the book's website. The website is also where the software is maintained. If you make meaningful contributions to this code, please go to the website to see how your improvements may be part of the next distribution. The software examples depicted in this book are protected by this book's copyright.
Requirements
Knowing HTML and the basics of how the Internet works will be necessary for using this book. If you are a beginning programmer with even nominal computer network experience, you'll be fine. It is important to recognize, however, that this book will not teach you how to program or how TCP/IP, the protocol of the Internet, works.
Hardware
You don't need elaborate hardware to start writing webbots. If you have a secondhand 33 MHz Pentium computer, you have the minimum requirement to play with all the examples in this book. Any of the following hardware is appropriate for using the examples and information in this book:
A personal computer that uses a Windows 95, Windows XP, or Windows Vista operating system
Any reasonably modern Linux-, Unix-, or FreeBSD-based computer
A Macintosh running OS X (or later)
It will also prove useful to have ample storage. This is particularly