regexp.7 (2184B)

1 .TH REGEXP 7 2 .SH NAME 3 regexp \- Plan 9 regular expression notation 4 .SH DESCRIPTION 5 This manual page describes the regular expression 6 syntax used by the Plan 9 regular expression library 7 .IR regexp (3). 8 It is the form used by 9 .IR egrep (1) 10 before 11 .I egrep 12 got complicated. 13 .PP 14 A 15 .I "regular expression" 16 specifies 17 a set of strings of characters. 18 A member of this set of strings is said to be 19 .I matched 20 by the regular expression. In many applications 21 a delimiter character, commonly 22 .LR / , 23 bounds a regular expression. 24 In the following specification for regular expressions 25 the word `character' means any character (rune) but newline. 26 .PP 27 The syntax for a regular expression 28 .B e0 29 is 30 .IP 31 .EX 32 e3: literal | charclass | '.' | '^' | '$' | '(' e0 ')' 33 34 e2: e3 35 | e2 REP 36 37 REP: '*' | '+' | '?' 38 39 e1: e2 40 | e1 e2 41 42 e0: e1 43 | e0 '|' e1 44 .EE 45 .PP 46 A 47 .B literal 48 is any non-metacharacter, or a metacharacter 49 (one of 50 .BR .*+?[]()|\e^$ ), 51 or the delimiter 52 preceded by 53 .LR \e . 54 .PP 55 A 56 .B charclass 57 is a nonempty string 58 .I s 59 bracketed 60 .BI [ \|s\| ] 61 (or 62 .BI [^ s\| ]\fR); 63 it matches any character in (or not in) 64 .IR s . 65 A negated character class never 66 matches newline. 67 A substring 68 .IB a - b\f1, 69 with 70 .I a 71 and 72 .I b 73 in ascending 74 order, stands for the inclusive 75 range of 76 characters between 77 .I a 78 and 79 .IR b . 80 In 81 .IR s , 82 the metacharacters 83 .LR - , 84 .LR ] , 85 an initial 86 .LR ^ , 87 and the regular expression delimiter 88 must be preceded by a 89 .LR \e ; 90 other metacharacters 91 have no special meaning and 92 may appear unescaped. 93 .PP 94 A 95 .L . 96 matches any character. 97 .PP 98 A 99 .L ^ 100 matches the beginning of a line; 101 .L $ 102 matches the end of the line. 103 .PP 104 The 105 .B REP 106 operators match zero or more 107 .RB ( * ), 108 one or more 109 .RB ( + ), 110 zero or one 111 .RB ( ? ), 112 instances respectively of the preceding regular expression 113 .BR e2 . 114 .PP 115 A concatenated regular expression, 116 .BR "e1\|e2" , 117 matches a match to 118 .B e1 119 followed by a match to 120 .BR e2 . 121 .PP 122 An alternative regular expression, 123 .BR "e0\||\|e1" , 124 matches either a match to 125 .B e0 126 or a match to 127 .BR e1 . 128 .PP 129 A match to any part of a regular expression 130 extends as far as possible without preventing 131 a match to the remainder of the regular expression. 132 .SH "SEE ALSO" 133 .IR regexp (3)