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Regular Expressions: the Complete Tutorial Regular Expressions The Complete Tutorial Jan Goyvaerts Regular Expressions: The Complete Tutorial Jan Goyvaerts Copyright © 2006, 2007 Jan Goyvaerts. All rights reserved. Last updated July 2007. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the author. This book is published exclusively at http://www.regular-expressions.info/print.html Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information is provided on an “as is” basis. The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book. i Table of Contents Tutorial................................................................................................................ 1 1. Regular Expression Tutorial ......................................................................................................................................... 3 2. Literal Characters............................................................................................................................................................ 5 3. First Look at How a Regex Engine Works Internally .............................................................................................. 7 4. Character Classes or Character Sets............................................................................................................................. 9 5. The Dot Matches (Almost) Any Character ..............................................................................................................13 6. Start of String and End of String Anchors...............................................................................................................15 7. Word Boundaries..........................................................................................................................................................18 8. Alternation with The Vertical Bar or Pipe Symbol .................................................................................................21 9. Optional Items ..............................................................................................................................................................23 10. Repetition with Star and Plus ...................................................................................................................................24 11. Use Round Brackets for Grouping..........................................................................................................................27 12. Named Capturing Groups ........................................................................................................................................31 13. Unicode Regular Expressions...................................................................................................................................33 14. Regex Matching Modes .............................................................................................................................................42 15. Possessive Quantifiers ...............................................................................................................................................44 16. Atomic Grouping .......................................................................................................................................................47 17. Lookahead and Lookbehind Zero-Width Assertions...........................................................................................49 18. Testing The Same Part of a String for More Than One Requirement ..............................................................52 19. Continuing at The End of The Previous Match....................................................................................................54 20. If-Then-Else Conditionals in Regular Expressions ..............................................................................................56 21. XML Schema Character Classes ..............................................................................................................................59 22. POSIX Bracket Expressions ....................................................................................................................................61 23. Adding Comments to Regular Expressions...........................................................................................................65 24. Free-Spacing Regular Expressions...........................................................................................................................66 Examples........................................................................................................... 67 1. Sample Regular Expressions.......................................................................................................................................69 2. Matching Floating Point Numbers with a Regular Expression ............................................................................72 3. How to Find or Validate an Email Address.............................................................................................................73 4. Matching a Valid Date .................................................................................................................................................76 5. Matching Whole Lines of Text...................................................................................................................................77 6. Deleting Duplicate Lines From a File.......................................................................................................................78 8. Find Two Words Near Each Other...........................................................................................................................79 9. Runaway Regular Expressions: Catastrophic Backtracking...................................................................................80 10. Repeating a Capturing Group vs. Capturing a Repeated Group........................................................................85 Tools & Languages........................................................................................... 87 1. Specialized Tools and Utilities for Working with Regular Expressions ..............................................................89 2. Using Regular Expressions with Delphi for .NET and Win32.............................................................................91 ii 3. EditPad Pro: Convenient Text Editor with Full Regular Expression Support ..................................................92 4. What Is grep?.................................................................................................................................................................95 5. Using Regular Expressions in Java ............................................................................................................................97 6. Java Demo Application using Regular Expressions..............................................................................................100 7. Using Regular Expressions with JavaScript and ECMAScript............................................................................107 8. JavaScript RegExp Example: Regular Expression Tester....................................................................................109 9. MySQL Regular Expressions with The REGEXP Operator..............................................................................110 10. Using Regular Expressions with The Microsoft .NET Framework ................................................................111 11. C# Demo Application.............................................................................................................................................114 12. Oracle Database 10g Regular Expressions...........................................................................................................121 13. The PCRE Open Source Regex Library...............................................................................................................123 14. Perl’s Rich Support for Regular Expressions.......................................................................................................124 15. PHP Provides Three Sets of Regular Expression Functions ............................................................................126 16. POSIX Basic Regular Expressions........................................................................................................................129 17. PostgreSQL Has Three Regular Expression Flavors .........................................................................................131 18. PowerGREP: Taking grep Beyond The Command Line ..................................................................................133 19. Python’s re Module ..................................................................................................................................................135 20. How to Use Regular Expressions in REALbasic................................................................................................139 21. RegexBuddy: Your Perfect Companion for Working with Regular Expressions..........................................142
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