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Regular Expressions are for Everyone 3You don’t need to be a programmer to use them, but if you do get into programming, every modernlanguage has an implementation of regexes, as they are incredibly useful for virtually any applicationyou can imagine.The main caveat is that each language – Javascript, Ruby, Perl, .NET – has small variations. Thisbook, however, focuses on the general uses of regexes that are more or less universal across all themajor languages. (I’ll be honest: I can’t even remember the differences among regex flavors, becauseit’s rarely an issue in daily usage).What special program will I need to use regexes?You’ll need a text editor that supports regular expressions. Nearly all text-editors that are aimedtowards coders support regular expressions. In the first chapter, I list the free (and powerful) texteditors for all the major operating systems.Beyond understanding the syntax, actually using the regular expressions requires nothing more thandoing a Find-and-Replace in the text editor, with the “use regular expressions” checkbox checked.What are the actual uses of regular expression?Because regexes are as easy as Find-and-Replace, the first chapters of this book will show howregexes can be used to replace patterns of text: for example, converting a list of dates in MM/DD/YYYYformat to YYYY-MM-DD. Later on, we’ll show how this pattern-matching power can be used to turnunstructured blocks of text into usable spreadsheet data, and how to turn spreadsheet data intowebpages.I have hopes that by the end of this book, regexes will become a sort of “gateway drug” for youto seek out even better, more powerful ways to explore the data and information in your life. Theexercises in this book can teach you how to find needles in a haystack – a name, a range of dates, arange of currency amounts, amid a dense text. But once you’ve done that, why settle for searchingone haystack – a document, in this case – when you could apply your regex knowledge to searchthousands or millions of haystacks?Regular expressions, for all their convoluted sea-of-symbols syntax, are just patterns. Learningthem is a small but non-trivial step toward realizing how much of our knowledge and experience iscaptured in patterns. And how, knowing these patterns, we can improve the way we sort and filterthe information in our lives.This book is a spinoff of the Bastards Book of Ruby, which devoted an awkwardly-long chapter tothe subject². You can get a preview of what this book will cover by checking out that (unfinished)chapter³.²http://ruby.bastardsbook.com/chapters/regexes/³http://ruby.bastardsbook.com/chapters/regexes/
Regular Expressions are for Everyone 4If you have any questions, feel free to mail me at dan@danwin.com⁴• Dan Nguyen @dancow⁵, danwin.com⁶⁴mailto:dan@danwin.com⁵https://twitter.com/dancow⁶http://danwin.com
Page 1: The Bastards Book ofRegular Express
Page 5 and 6: CONTENTSOptionality and alternation
Page 7 and 8: CONTENTSSwitching visualizations (T
Page 9: Regular Expressions are for Everyon
Page 13 and 14: Getting Started6
Page 15 and 16: Finding a proper text editor 8Notep
Page 17 and 18: Finding a proper text editor 10Edit
Page 19 and 20: Finding a proper text editor 12Text
Page 21 and 22: Finding a proper text editor 14does
Page 23 and 24: Finding a proper text editor 16Yest
Page 25 and 26: Finding a proper text editor 18A do
Page 27 and 28: A better Find-and-Replace 20The lim
Page 29 and 30: A better Find-and-Replace 22Using R
Page 31 and 32: Your first regex 24helloThe Find-an
Page 33 and 34: Your first regex 26The regex syntax
Page 35 and 36: Your first regex 28Double-bounded
Page 37 and 38: Your first regex 30AnswerFind \bcat
Page 39 and 40: Removing emptinessIt’s funny how
Page 41 and 42: Removing emptiness 34Now let’s do
Page 43 and 44: Removing emptiness 36…as opposed
Page 45 and 46: Removing emptiness 38Replacement in
Page 47 and 48: Match one-or-more with the plus sig
Page 55 and 56: Match zero-or-more with the star si
Page 57 and 58: Specific and limited repetition 501
Page 59 and 60: Specific and limited repetition 52E
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Specific and limited repetition 54C
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Anchors: A way to trim emptinessIn
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Anchors: A way to trim emptiness 58
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Matching any letter, any number 64A
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Matching any letter, any number 66W
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Matching any letter, any number 68[
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Matching any letter, any number 70R
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Matching any letter, any number 72F
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Matching any letter, any number 74A
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Negative character sets 76$1,200.00
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Negative character sets 78\W+Exerci
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Capture, Reuse 80Find (ba)+Matches
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Capture, Reuse 82.- then the 1st ba
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Capture, Reuse 84In English We are
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Capture, Reuse 86ApplesOraclesOrang
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Capture, Reuse 8805-14-8912-03-9803
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Capture, Reuse 90Mary asked: "What
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Optionality and alternationThe two
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Optionality and alternation 94Answe
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Optionality and alternation 96Studi
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Optionality and alternation 98You m
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Laziness and greediness 100Being to
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Laziness and greediness 102Replace
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Laziness and greediness 104With the
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Lookarounds 106cat(?=s)- will match
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Lookarounds 108`(?
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Lookarounds 110ExerciseGiven the fo
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Lookarounds 112City,CountryAlbuquer
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Lookarounds 114Given this list of c
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Lookarounds 116100,J.D. Salinger Av
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Lookarounds 1186,300|Apples|New Yor
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Lookarounds 120^(\d+) Record ID (\w
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Lookarounds 122d. Remove all asides
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From Data to HTML (TODO)This chapte
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From Data to HTML (TODO) 126Turning
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The ExercisesI’ve never been one
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Data Cleaning with the Stars 130LOR
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Data Cleaning with the Stars 132[GM
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Finding needles in haystacks (TODO)
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Changing phone format (TODO)Todo: T
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Changing phone format (TODO) 138Exe
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Changing phone format (TODO) 140Ans
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Changing phone format (TODO) 142`1-
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Changing phone format (TODO) 144(\d
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Dating, Associated Press Style (TOD
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Sorting a police blotter 154Sloppy
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Sorting a police blotter 156I used
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Converting XML to tab-delimited dat
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Converting XML to tab-delimited dat
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Cleaning up Microsoft Word HTML(TOD
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Cleaning up OCR Text (TODO)Image sc
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Moving forwardThank you for taking
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