Mastering Regular Expressions - Table of Contents

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Page vi Regular Expression Nomenclature 24 Improving on the Status Quo 26 Summary 28 Personal Glimpses 30 2: Extended Introductory Examples 31 About the Examples 32 A Short Introduction to Perl 33 Matching Text with Regular Expressions 34 Toward a More Real-World Example 36 Side Effects of a Successful Match 36 Intertwined Regular Expressions 39 Intermission 43 Modifying Text with Regular Expressions 45 Automated Editing 47 A Small Mail Utility 48 That Doubled-Word Thing 54 3: Overview of Regular Expression Features and Flavors. 59
A Casual Stroll Across the Regex Landscape 60 The World According to Grep 60 The Times They Are a Changin' 61 At a Glance 63 POSIX 64 Care and Handling of Regular Expressions 66 Identifying a Regex 66 Doing Something with the Matched Text 67 Other Examples 67 Care and Handling: Summary 70 Engines and Chrome Finish 70 Chrome and Appearances 71 Engines and Drivers 71 Common Metacharacters 71 Character Shorthands 72 Strings as Regular Expression 75 Class Shorthands, Dot, and Character Classes 77 Anchoring 81
Page 1 and 2: Mastering Regular Expressions - Tab
Page 3 and 4: Mastering Regular Expressions by Je
Page 5: Optional Items 16 Other Quantifiers
Page 9 and 10: Page vii Alternation 84 Guide to th
Page 11 and 12: POSIX and the Longest-Leftmost Rule
Page 13 and 14: More Work for a POSIX NFA 147 Work
Page 15 and 16: Page ix The Real "Unrolling the Loo
Page 17 and 18: A Chapter, a Chicken, and The Perl
Page 19 and 20: The Match Operator 246 Match-Operan
Page 21 and 22: Page xi The Efficiency Penalty of t
Page 23 and 24: 6-5 GNU Emacs's Search-Related Prim
Page 25 and 26: Preface This book is about a powerf
Page 27 and 28: Anyone who uses GNU Emacs or vi, or
Page 29 and 30: This book tells a story, but one wi
Page 31 and 32: • Chapter 2, Extended Introductor
Page 33 and 34: • Chapter 7, Perl Regular Express
Page 35 and 36: To make this useful, we can wrap Su
Page 37 and 38: Knowing I would have to write about
Page 39 and 40: The work of many reviewers has help
Page 41 and 42: I'd like to thank my company, Omron
Page 43 and 44: 1 Introduction to Regular Expressio
Page 45 and 46: Page 2 remove, isolate, and general
Page 47 and 48: an editor would have been truly ard
Page 49 and 50: Regular Expressions as a Language P
Page 51 and 52: The Language Analogy Page 5 Full re
Page 53 and 54: The goal of this book Page 6 The ch
Page 55 and 56: Searching Text Files: Egrep Page 7
Page 57 and 58:
ytes and lines in a file, but it ge
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Character Classes Matching any one
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Answers to the questions on page 8.
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With 07.04.76 , the dots are metach
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*Once, in fourth grade, I was leadi
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As you can see, the alternation hap
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Figure 1-2: Start and end of "word"
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Optional Items Page 16 Let's look a
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Other Quantifiers: Repetition Page
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Page 18 This leaves us with , whic
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easier to tell egrep to ignore case
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Answer to the question on page 18.
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Page 21 The metasequence to match a
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Page 22 Also, while egrep doesn't c
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Dollar amount (with optional cents)
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"Subexpression" The term subexpress
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When it comes down to it, regular e
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• Regular expression features—S
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• A negated character class is st
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Remember, though, that a backslash
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2 Extended Introductory Examples In
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About the Examples Page 32 Perl all
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A Short Introduction to Perl Page 3
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Here's how it looks: % perl -w temp
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Page 35 Note that a test such as $r
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Toward a More Real-World Example Pa
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Page 37 To keep the example unclutt
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Figure 2-2: Temperature-conversion
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Negated matches Our program logic h
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Page 40 ostensibly used only to gro
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A short aside—metacharacters galo
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How do [ ] * and ( *| *) compare? A
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Page 43 Oops! Did you notice that i
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Page 127 and 128:
Modifying Text with Regular Express
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Just what does $var = s/\bJeff\b/Je
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Page 47 I boiled down my needs to '
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Page 48 Although I applied this to
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Page 49 Let's analyze this. To prin
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the end of the string. * We can't u
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A Warning about .* The expression .
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Page 52 header, we'll overwrite $re
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Page 53 The substitute searches for
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The "real" real world Page 54 Email
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Double-word example in modern Perl
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Page 56 The next unless before the
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There's nothing special about Perl
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Page 58 Another interesting thing i
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It didn't make sense to talk about
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* "A logical calculus of the ideas
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Along the way, AT&T Bell Labs added
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Multiply this by the passage of tim
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Many issues must be kept in mind, e
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Page: Page 65 implementation, befor
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Page: Page 66 standard C library fu
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Doing Something with the Matched Te
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Page 68 The early versions of awk d
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Page 69 expression for finding doub
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You can guess that the string with
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Page 71 in every decision the drive
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Page 72 Some tools add a lot of new
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Table 3-3: A Few Utilities and Some
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Octal escape \ num Page 74 Some imp
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Are these escapes literal? Page 75
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Page 76 metacharacters take precede
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Page 77 within a class, [^\"] must
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Emacs syntax classes Page 78 As an
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In many tools, the only metacharact
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POSIX bracket-expression "character
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POSIX bracket-expression "collating
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Table 3-4. String/Line Anchors, and
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Page 83 Each tool has its own idea
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Intervals {min,max} or \{min,max\}
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Page 85 happens is different for mo
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Page 86 an expert to solve Fermat's
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Well, what if you had an electric c
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Both engine types have been around
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On the other hand, egrep, awk, and
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About the Examples Page 91 This cha
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attempted at each position all the
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Engine Pieces and Parts Page 93 An
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Page 94 they are irrelevant to an e
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Page 95 If it turns out that the on
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So, with a variable $line holding a
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You might even imagine something li
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Page 98 first try to take as much a
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Regex-Directed vs. Text-Directed Th
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DFA Engine: Text-Directed Contrast
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Page 101 lady sings." in this parag
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Page 102 The regex-directed nature
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Page 103 regex from the second posi
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NFA: Theory vs. Reality The true ma
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that had been saved as the untried
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a num a num a num a num These repre
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A few observations: first, the back
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Page 109 Actually, since we underst
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Laziness? Page 110 This whole probl
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I then noted: Anything matched so f
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Is Alternation Greedy? Page 112 The
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Is Alternation Greedy? Page 112 The
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Uses for Non-Greedy Alternation Pag
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Let me repeat: when the transmissio
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To match continuation lines, you mi
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(to|top)(o|polo)?(gical|o?logical)
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Differences in match speed For simp
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* I have seen two tools employ slig
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Simple, however, does not necessari
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Page 122 Even in a script, efficien
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Page 123 The problem with (\\\n|[^\
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Page 124 simple expression he used
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Page 125 worth the trouble to be mo
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with the … example from page 109.
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Indeed, this matches such examples
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The solution is to add an alternati
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3. match the ending delimiter As I
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This is not a problem when using a
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One practical problem is that our r
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Stating problems in a way that make
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The transmission kicks in and retri
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This is a good time to point out th
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if [regexp -indices .*/ $WholePath
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One overriding rule regardless of e
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Constructing a regex for a specific
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Toward arming you well, this chapte
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Let's start by looking at an exampl
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More Advanced—Localizing the Gree
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Figure 5-2: Effects of an added plu
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Well, you get the idea—there are
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On a local level, backtracking is r
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The remembered states accumulated w
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As a comparison, let's replace the
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Figure 5-4: Failing attempt to matc
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As we see with alternation (among o
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The differences lie in what is matc
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Example #3 involves much less overh
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The explanation lies in another rea
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One moral to learn from all this is
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GNU Emacs performs very few of the
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Somewhat related to a fixed-string
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Finally, how do we explain the resu
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If a regex is used in a situation w
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The compiled form can be used multi
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Page 160 keeps a cache of the inter
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Page 161 The doublequotes are for t
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Page 162 If the engine had the matc
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possible, but we can still identify
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First, the special and normal subex
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+ \{[^}]*\} Plugging this into the
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• ( *\$[0-9]+)* , to match space-
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If a subdomain is [a-z]+ and we wan
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• more speed The regex "flows" we
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Our pseudo comments, with /x and x/
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Let's try to fix these regexes. Wit
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For efficiency's sake, let's look a
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Other Quantifiers: Repetition Page
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The Freeflowing Regex Page 173 We j
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Consider: set COMMENT {/\*[^*]*\*+(
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Page 175 So rather than letting the
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These changes yield "($OTHER+|$DOUB
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Think! Figure 5-9: Well-guided opti
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Page 178 On the other hand, if the
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Page 179 the string where [cdsuw] c
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Page 180 When it comes down to it,
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Yes, even something as simple as gr
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The -i command-line option seems to
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Page 184 string when a regex matche
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With versions of awk that support h
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Some implementations have limitatio
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string = "awk" gsub(/(nothing)*/, "
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Tcl* uses Henry Spencer's NFA regex
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How Tcl parses a script is one of t
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Here, the -nocase is an option that
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Despite the documentation to the co
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Emacs has long used a Traditional N
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Table 6-6: GNU Emacs's String Metac
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Page 195 The syntax influences the
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Page 196 For example, during a POSI
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Page 197 The match-string and repla
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Code for Emacs function for Chapter
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7 Perl Regular Expressions In this
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Page 200 Perhaps more important tha
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The Perl Way Page 201 Table 7-1 sum
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The richness of variety and options
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In the same article, Larry also wro
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Perl's full toolbox offers many sol
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Page 206 These are easy enough to u
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Page 207 Well, almost all the field
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Page 208 Of course, being able to s
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Page 209 Those comments are actuall
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Regex-Related Perlisms Page 210 The
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Page 211 Sometimes, the type of an
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Dynamically scoped values Page 212
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Page 213 An automatic save and rest
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Page 214 You'd get the same effect
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Dynamic Scope Example # Process "th
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Page 216 The benefits of dynamic sc
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Page 217 Perlmaster.) This code cou
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$1, $2, $3, etc. Page 218 The text
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Using $1 within a regex? Page 219 T
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The doublequotes are really operato
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Page 221 Thus, you might consider ^
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Page 222 once when the script is fi
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Figure 7-1: Perl parsing, from prog
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the operand this is different from
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Perl's Regex Flavor Page 225 Now th
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Let's say you want to specially pro
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• The possibility of greater inte
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Matches a number if not followed by
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Using capturing parentheses within
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Page 231 (?#…) appeared in versio
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String Anchors Anchors are indispen
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• Whether you can work with data
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To allow greater flexibility, Perl5
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Combining both /s and /m has /m tak
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Keeping the match in synch with exp
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Page 238 bump-along-and-retry happe
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Page 239 These methods work, but fr
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Page 240 This example is simple, bu
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a \W character). For example, an $i
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If compiled with appropriate librar
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Perl's class sublanguage is unique
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Sorting is a practical use of this
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Second-class metacharacters As far
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Match-Operand Delimiters Page 247 I
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Page 248 This can be useful if you
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Match Modifiers Page 249 The match
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Page 250 Except when used with the
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Page 251 true or false value that i
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Match Operator Return Value Page 25
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List context, with the /g modifier
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Outside Influences on the Match Ope
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The Substitution Operator Page 255
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The /e Modifier Page 257 Only the s
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eieio Page 258 Perhaps useful only
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conditional of an if), the return v
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Page 260 rather than m/…/ is used
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Advanced Split Page 261 Because spl
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Page 262 list are stripped; others
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Page 263 nothingness at the end of
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Any general scalar expression as th
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lems as the full regex becomes some
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choices. Page 266 • Interpolation
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and not very "interesting" in and o
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Regex Compilation, the /o Modifier,
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Now, let's consider the following s
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Page 270 Unfortunately, it's usuall
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Page 271 This example takes advanta
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# Create a function to check a bunc
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Page 273 It's a nice idea, but ther
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Particularly with the /e modifier,
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Recall that the match operator retu
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Basic Split split is an operator th
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Perl must make a copy to support an
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On the other hand, in true worst-ca
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If you can be sure these variables
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The result of these two steps is a
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Page 280 By the way, I forgot to me
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Final words about the /i penalty Pa
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is then computed ('100C' in this ca
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Figure 7-2: Applying s//Tom/ to 'De
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Page 284 Any substitution using the
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Page 285 The biggest change is that
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Literal text cognizance Page 286 Ma
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stclass ':kind' plus Page 287 Indic
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Page 288 When you study a string, P
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When study can help Page 289 study
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Along with the CSV question, many o
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Adding Commas to a Number People of
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It's challenging to see how crisply
Page 603 and 604:
With the same tests as Chapter 5's
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ut it's not so easy. While evaluati
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$username = '\w+'; $hostname = '\w+
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That last item, $atom, might need s
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You'll not find comment, item 22, e
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aperiod >; # Item 2: addr-spec is l
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Unlike all the other constructs so
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$esc . (?: com | edu | gov | … |
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$sep = qq< (?: [$space$tab + # for
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Back in $route, after the first $do
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^Subject|From|Date: (.*) is very di
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Another feature I've found an occas
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Page 217 The special variables $&,
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Perl4 Note #10 Page 247 With Perl4,
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Perl4 Note #10 Page 247 With Perl4,
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Page 255 Although Perl4's match ope
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Page 264 With Perl4, the default op
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O'Reilly & Associates Page 310 O'Re
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http://www.cs.umd.edu/users/dfs/jav
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http://www.python.org/ The Python L
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; (?: $quoted_pair | $Cnested ) # s
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# Item 9. sub-domain is a domain-re
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; )* $phrase_char * # more "normal"
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Enjoy!
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xx, 40, 42, 187, 197 (see also \t (
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introduction 42 equivalence to char
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i (see Perl, modifier: case insensi
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. (see dot) ? (see question mark) [
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analogy backtracking bread crumbs 1
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anchor (see line anchor; word ancho
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line anchors 82 mawk 90, 161, 185 o
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POSIX NFA example 147 pseudo-backtr
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ignoring differences (see case-inse
Page 669 and 670:
character, encoding (cont'd) ISO-20
Page 671 and 672:
CheckNaughtiness 279 checkpoint (se
Page 673 and 674:
non-greedy vs. negated character cl
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delimiter (see regex delimiter) Del
Page 677 and 678:
doublequoted string allowing escape
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efficiency (cont'd) egrep 7 substit
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email for MacOs 312 match-data 196-
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errata (for this book) 309 escape 2
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a*((ab)*|b*) 113 [a-zA-Z_][a-zA-Z_0
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'M.I.T.' 83 [.\n] 131 'NE14AD8' 83
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ExtUtils::Liblist module 278 ExtUti
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patterns (globs) 4 prepending to li
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freeflowing regex 173-174 free-form
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GNU (cont'd) egrep 120 and backrefe
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H in awk 68, 187 Haertel, Mike 90 H
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shortest branch first 39 vs. while
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Japanese character encoding 26 font
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ignoring case (see case-insensitive
Page 705 and 706:
list context 210 literal text 5 mat
Page 707 and 708:
Masuda, Keith xxiii match (see Perl
Page 709 and 710:
neverending 144, 160, 162, 175, 296
Page 711 and 712:
doublequoted string in Emacs 76 ema
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Perl, line mode) modifier (see Perl
Page 715 and 716:
newgetopt.pl package 278 newline an
Page 717 and 718:
nonregular sets 104 normal (see unr
Page 719 and 720:
first-character discrimination 151,
Page 721 and 722:
O'Reilly & Associates lex & yacc 8
Page 723 and 724:
Pascal 32, 54, 120 format 35 matchi
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people (cont'd) Hietaniemi, Jarkko
Page 727 and 728:
Spencer, Henry xxii-xxiii, 62, 120-
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s/…/…/ (see Perl, substitution)
Page 731 and 732:
$0 218 $1 216-219, 257, 282-283 ?
Page 733 and 734:
processing 221 variables appearing
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Perl (cont'd) line mode and /m 231-
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modifier: case insensitive (/i) 42,
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Text:: ParseWords module 207, 278 m
Page 741 and 742:
-n 32 -p 47 -w 34, 213, 285 parenth
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s/…/…/ (see Perl, substitution)
Page 745 and 746:
Perl, substitution (cont'd) other m
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acket expressions 79 C library supp
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Communications of the ACM 60 Compil
Page 751 and 752:
Q group(1) 58, 70, 83, 96 gsub 58 h
Page 753 and 754:
x{0,0} 84 minimal matching 83 multi
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questions (cont'd) slicing a 24-hou
Page 757 and 758:
listing of programs and types 90 te
Page 759 and 760:
Python in Tcl 75, 189, 193 named su
Page 761 and 762:
efficiency 118 essence 102 and gree
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scalar context (see Perl, context)
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single-line mode (see Perl, modifie
Page 767 and 768:
string (cont'd) in Emacs 69, 75 in
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chart of shorthands 73 flavor chart
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Test::Harness module 278 testlib mo
Page 773 and 774:
unmatching (see backtracking) unrol
Page 775 and 776:
while vs. foreach vs. if 256 whites
Page 777 and 778:
About the Author Page 343 Jeffrey F
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Page 344 their prey in dim or dark
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