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gerrit.morgengrauen.info / mudlib-public / 88f12479d30902b0d2c05be41901c96b92a88a77 / . / doc / concepts / regexp
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MG Mud User88f12472016-06-24 23:31:02 +0200[diff] [blame^]1SYNOPSIS
2 Regular Expressions
3
4
5DESCRIPTION
6 LDMud supports both the traditional regular expressions as
7 implemented by Henry Spencer ("HS" or "traditional"), and the
8 Perl-compatible regular expressions by Philip Hazel ("PCRE").
9 Both packages can be used concurrently, with the selection
10 being made through extra option flags argument to the efuns.
11 One of the two packages can be selected at compile time, by
12 commandline argument, and by driver hook to be the default
13 package.
14
15 The packages differ in the expressivity of their expressions
16 (PCRE offering more options that Henry Spencer's package),
17 though they both implement the common subset outlined below.
18
19 All regular expression efuns take an additional options
20 parameter, which is a an number composed of bitflags, and is
21 used to modify the exact behaviour of the expression
22 evaluation. In addition, certain efuns may accept additional
23 specific options.
24
25 For details, refer to the detailed manpages: hsregexp(C) for
26 the Henry Spencer package, pcre(C) for the PCRE package.
27
28
29REGULAR EXPRESSION DETAILS
30 A regular expression is a pattern that is matched against a
31 subject string from left to right. Most characters stand for
32 themselves in a pattern, and match the corresponding charac-
33 ters in the subject. As a trivial example, the pattern
34
35 The quick brown fox
36
37 matches a portion of a subject string that is identical to
38 itself. The power of regular expressions comes from the
39 ability to include alternatives and repetitions in the pat-
40 tern. These are encoded in the pattern by the use of meta-
41 characters, which do not stand for themselves but instead
42 are interpreted in some special way.
43
44 The following metacharacters are 'universal' in that both regexp
45 packages understand them in the same way:
46
47 . Match any character.
48
49 ^ Match begin of line.
50
51 $ Match end of line.
52
53 x|y Match regexp x or regexp y.
54
55 () Match enclosed regexp like a 'simple' one.
56
57 x* Match any number (0 or more) of regexp x.
58
59 x+ Match any number (1 or more) of regexp x.
60
61 [..] Match one of the characters enclosed.
62
63 [^ ..] Match none of the characters enclosed. The .. are to
64 replaced by single characters or character ranges:
65
66 [abc] matches a, b or c.
67
68 [ab0-9] matches a, b or any digit.
69
70 [^a-z] does not match any lowercase character.
71
72 \B not a word boundary
73
74 \c match character c even if it's one of the special
75 characters.
76
77 The following metacharacters or metacharacter combinations implement
78 similar functions in the two regexp packages;
79
80 \b PCRE: word boundary, also used inconjunction with
81 \w (any "word" character) and \W (any "non-word"
82 character).
83
84 \< HS: Match begin of word.
85 \> HS: Match end of word.
86
87
88OPTIONS
89 The package is selected with these option flags:
90
91 RE_PCRE
92 RE_TRADITIONAL
93
94 These flags are also used for the H_REGEXP_PACKAGE driver
95 hook.
96
97
98 Traditional regular expressions understand one option:
99
100 RE_EXCOMPATIBLE
101
102
103 PCRE understands these options:
104
105 RE_ANCHORED
106 RE_CASELESS
107 RE_DOLLAR_ENDONLY
108 RE_DOTALL
109 RE_EXTENDED
110 RE_MULTILINE
111 RE_UNGREEDY
112 RE_NOTBOL
113 RE_NOTEOL
114 RE_NOTEMPTY
115
116HISTORY
117 LDMud 3.3.596 implemented the concurrent use of both packages.
118
119SEE ALSO
120 hsregexp(C), pcre(C), regexp_package(H), regexp(E), regexplode(E),
121 regmatch(E), regreplace(E), regexp_package(E), invocation(D)