Jeffrey E. F. Friedl - Mastering Regular Expressions

Programming

This book will get you up to speed on the productivity secrets that will make your life easier: regular expressions. Well-crafted regular expressions can reduce hours of tedious labor to a 15-second solution. Now a standard feature in a wide range of languages and popular toolsincluding Perl, PHP, Java, Python, Ruby, MySQL, VB.NET, and C# (and any language using the .NET Framework)regular expressions will allow you to code complex and subtle text processing that you never imagined could be automated.

Mastering Regular Expressions, Third Edition, now includes material on PHP and its powerful regular expressions. This edition has been updated throughout to reflect advances in other languages, including expanded in-depth coverage of Suns java.util.regex, with special attention to the many differences between Java 1.4.2 and Java 1.5/1.6.

Topics include:

• A comparison of features among many languages and tools
• How a regular expression engine works
• Optimization (major savings available here!)
• Matching only what you want, not what you dont
• Sections and chapters on individual languages

Written in the lucid, entertaining lone that makes a complex topic become crystal clear to programmers, and filled with solutions to difficult real-world problems, Mastering Regular Expressions, Third Edition, offers a wealth of information that you can put to immediate use to craft elegant, time-saving solutions to a wide range of issues.

If you use regular expressions as part of your professional work (even if you already have a good book on whatever language youre programming in) I would strongly recommend this book to you.

Dr Chris Brown, Linux Format

Mastering Regular Expressions is the definitive guide to the subject, and an outstanding resource that belongs on every programmers bookshelf. Ten out of Ten Horseshoes.

Jason Menard, Java Ranch

There isnt a better (or more useful) book available on regular expressions.

Zak Greant, Planet PHP

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Mastering Regular Expressions

Third Edition

Jeffrey E. F. Friedl

OREILLY

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Mastering Regular Expressions, Third Edition
by Jeffrey E. F. Friedl

Copyright 2006, 2002, 1997 OReilly Media, Inc. All rights reserved.
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Editor: Andy Oram

Production Editor: Jeffrey E. F. Friedl

Cover Designer: Edie Freedman

Printing History:

Nutshell Handbook, the Nutshell Handbook logo, and the OReilly logo are registered trademarks of OReilly Media, Inc. Mastering Regular Expressions, the image of owls, and related trade dress are trademarks of OReilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and OReilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps.

While every precaution has been taken in the preparation of this book, the publisher and author assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

This book uses RepKover, a durable and flexible lay-at binding.

ISBN: 0-596-52812-4
[M]

FOR

For putting up with me.

And for the years I worked on this book,

for putting up without me.

This book is about a powerful tool called regular expressions. It teaches you how to use regular expressions to solve problems and get the most out of tools and languages that provide them. Most documentation that mentions regular expressions doesnt even begin to hint at their power, but this book is about mastering regular expressions.

Regular expressions are available in many types of tools (editors, word processors, system tools, database engines, and such), but their power is most fully exposed when available as part of a programming language. Examples include Java and JScript, Visual Basic and VBScript, JavaScript and ECMAScript, C, C++, C#, elisp, Perl, Python, Tcl, Ruby, PHP, sed, and awk. In fact, regular expressions are the very heart of many programs written in some of these languages.

Theres a good reason that regular expressions are found in so many diverse languages and applications: they are extremely powerful. At a low level, a regular expression describes a chunk of text. You might use it to verify a users input, or perhaps to sift through large amounts of data. On a higher level, regular expressions allow you to master your data. Control it. Put it to work for you. To master regular expressions is to master your data.

I finished the first edition of this book in late 1996, and wrote it simply because there was a need. Good documentation on regular expressions just wasnt available, so most of their power went untapped. Regular-expression documentation was available, but it centered on the low-level view. It seemed to me that they were analogous to showing someone the alphabet and expecting them to learn to speak.

The five and a half years between the first and second editions of this book saw the popular rise of the Internet, and, perhaps more than just coincidentally, a considerable expansion in the world of regular expressions. The regular expressions of almost every tool and language became more powerful and expressive. Perl, Python, Tcl, Java, and Visual Basic all got new regular-expression backends. New languages with regular expression support, like PHP, Ruby, and C#, were developed and became popular. During all this time, the basic core of the book how to truly understand regular expressions and how to get the most from them remained as important and relevant as ever.

Yet, the first edition gradually started to show its age. It needed updating to reflect the new languages and features, as well as the expanding role that regular expressions played in the Internet world. It was published in 2002, a year that saw the landmark releases of java.util.regex