1 058b0118 2005-01-03 devnull .TH REGEXP 7
  2 cfa37a7b 2004-04-10 devnull .SH NAME
  3 058b0118 2005-01-03 devnull regexp \- Plan 9 regular expression notation
  4 cfa37a7b 2004-04-10 devnull .SH DESCRIPTION
  5 cfa37a7b 2004-04-10 devnull This manual page describes the regular expression
  6 cfa37a7b 2004-04-10 devnull syntax used by the Plan 9 regular expression library
  7 d32deab1 2020-08-16 rsc .MR regexp (3) .
  8 cfa37a7b 2004-04-10 devnull It is the form used by
  9 d32deab1 2020-08-16 rsc .MR egrep (1)
 10 cfa37a7b 2004-04-10 devnull before
 11 cfa37a7b 2004-04-10 devnull .I egrep
 12 cfa37a7b 2004-04-10 devnull got complicated.
 13 cfa37a7b 2004-04-10 devnull .PP
 14 cfa37a7b 2004-04-10 devnull A 
 15 cfa37a7b 2004-04-10 devnull .I "regular expression"
 16 cfa37a7b 2004-04-10 devnull specifies
 17 cfa37a7b 2004-04-10 devnull a set of strings of characters.
 18 cfa37a7b 2004-04-10 devnull A member of this set of strings is said to be
 19 cfa37a7b 2004-04-10 devnull .I matched
 20 cfa37a7b 2004-04-10 devnull by the regular expression.  In many applications
 21 cfa37a7b 2004-04-10 devnull a delimiter character, commonly
 22 cfa37a7b 2004-04-10 devnull .LR / ,
 23 cfa37a7b 2004-04-10 devnull bounds a regular expression.
 24 cfa37a7b 2004-04-10 devnull In the following specification for regular expressions
 25 cfa37a7b 2004-04-10 devnull the word `character' means any character (rune) but newline.
 26 cfa37a7b 2004-04-10 devnull .PP
 27 cfa37a7b 2004-04-10 devnull The syntax for a regular expression
 28 cfa37a7b 2004-04-10 devnull .B e0
 29 cfa37a7b 2004-04-10 devnull is
 30 cfa37a7b 2004-04-10 devnull .IP
 31 cfa37a7b 2004-04-10 devnull .EX
 32 cfa37a7b 2004-04-10 devnull e3:  literal | charclass | '.' | '^' | '$' | '(' e0 ')'
 33 cfa37a7b 2004-04-10 devnull 
 34 cfa37a7b 2004-04-10 devnull e2:  e3
 35 cfa37a7b 2004-04-10 devnull   |  e2 REP
 36 cfa37a7b 2004-04-10 devnull 
 37 cfa37a7b 2004-04-10 devnull REP: '*' | '+' | '?'
 38 cfa37a7b 2004-04-10 devnull 
 39 cfa37a7b 2004-04-10 devnull e1:  e2
 40 cfa37a7b 2004-04-10 devnull   |  e1 e2
 41 cfa37a7b 2004-04-10 devnull 
 42 cfa37a7b 2004-04-10 devnull e0:  e1
 43 cfa37a7b 2004-04-10 devnull   |  e0 '|' e1
 44 cfa37a7b 2004-04-10 devnull .EE
 45 cfa37a7b 2004-04-10 devnull .PP
 46 cfa37a7b 2004-04-10 devnull A
 47 cfa37a7b 2004-04-10 devnull .B literal
 48 cfa37a7b 2004-04-10 devnull is any non-metacharacter, or a metacharacter
 49 cfa37a7b 2004-04-10 devnull (one of
 50 cfa37a7b 2004-04-10 devnull .BR .*+?[]()|\e^$ ),
 51 cfa37a7b 2004-04-10 devnull or the delimiter
 52 cfa37a7b 2004-04-10 devnull preceded by 
 53 cfa37a7b 2004-04-10 devnull .LR \e .
 54 cfa37a7b 2004-04-10 devnull .PP
 55 cfa37a7b 2004-04-10 devnull A
 56 cfa37a7b 2004-04-10 devnull .B charclass
 57 cfa37a7b 2004-04-10 devnull is a nonempty string
 58 cfa37a7b 2004-04-10 devnull .I s
 59 cfa37a7b 2004-04-10 devnull bracketed
 60 cfa37a7b 2004-04-10 devnull .BI [ \|s\| ]
 61 cfa37a7b 2004-04-10 devnull (or
 62 cfa37a7b 2004-04-10 devnull .BI [^ s\| ]\fR);
 63 cfa37a7b 2004-04-10 devnull it matches any character in (or not in)
 64 cfa37a7b 2004-04-10 devnull .IR s .
 65 cfa37a7b 2004-04-10 devnull A negated character class never
 66 cfa37a7b 2004-04-10 devnull matches newline.
 67 cfa37a7b 2004-04-10 devnull A substring 
 68 cfa37a7b 2004-04-10 devnull .IB a - b\f1,
 69 cfa37a7b 2004-04-10 devnull with
 70 cfa37a7b 2004-04-10 devnull .I a
 71 cfa37a7b 2004-04-10 devnull and
 72 cfa37a7b 2004-04-10 devnull .I b
 73 cfa37a7b 2004-04-10 devnull in ascending
 74 cfa37a7b 2004-04-10 devnull order, stands for the inclusive
 75 cfa37a7b 2004-04-10 devnull range of
 76 cfa37a7b 2004-04-10 devnull characters between
 77 cfa37a7b 2004-04-10 devnull .I a
 78 cfa37a7b 2004-04-10 devnull and
 79 cfa37a7b 2004-04-10 devnull .IR b .
 80 cfa37a7b 2004-04-10 devnull In 
 81 cfa37a7b 2004-04-10 devnull .IR s ,
 82 cfa37a7b 2004-04-10 devnull the metacharacters
 83 cfa37a7b 2004-04-10 devnull .LR - ,
 84 cfa37a7b 2004-04-10 devnull .LR ] ,
 85 cfa37a7b 2004-04-10 devnull an initial
 86 cfa37a7b 2004-04-10 devnull .LR ^ ,
 87 cfa37a7b 2004-04-10 devnull and the regular expression delimiter
 88 cfa37a7b 2004-04-10 devnull must be preceded by a
 89 cfa37a7b 2004-04-10 devnull .LR \e ;
 90 cfa37a7b 2004-04-10 devnull other metacharacters 
 91 cfa37a7b 2004-04-10 devnull have no special meaning and
 92 cfa37a7b 2004-04-10 devnull may appear unescaped.
 93 cfa37a7b 2004-04-10 devnull .PP
 94 cfa37a7b 2004-04-10 devnull A 
 95 cfa37a7b 2004-04-10 devnull .L .
 96 cfa37a7b 2004-04-10 devnull matches any character.
 97 cfa37a7b 2004-04-10 devnull .PP
 98 cfa37a7b 2004-04-10 devnull A
 99 cfa37a7b 2004-04-10 devnull .L ^
100 cfa37a7b 2004-04-10 devnull matches the beginning of a line;
101 cfa37a7b 2004-04-10 devnull .L $
102 cfa37a7b 2004-04-10 devnull matches the end of the line.
103 cfa37a7b 2004-04-10 devnull .PP
104 cfa37a7b 2004-04-10 devnull The 
105 cfa37a7b 2004-04-10 devnull .B REP
106 cfa37a7b 2004-04-10 devnull operators match zero or more
107 cfa37a7b 2004-04-10 devnull .RB ( * ),
108 cfa37a7b 2004-04-10 devnull one or more
109 cfa37a7b 2004-04-10 devnull .RB ( + ),
110 cfa37a7b 2004-04-10 devnull zero or one
111 cfa37a7b 2004-04-10 devnull .RB ( ? ),
112 cfa37a7b 2004-04-10 devnull instances respectively of the preceding regular expression 
113 cfa37a7b 2004-04-10 devnull .BR e2 .
114 cfa37a7b 2004-04-10 devnull .PP
115 cfa37a7b 2004-04-10 devnull A concatenated regular expression,
116 cfa37a7b 2004-04-10 devnull .BR "e1\|e2" ,
117 cfa37a7b 2004-04-10 devnull matches a match to 
118 cfa37a7b 2004-04-10 devnull .B e1
119 cfa37a7b 2004-04-10 devnull followed by a match to
120 cfa37a7b 2004-04-10 devnull .BR e2 .
121 cfa37a7b 2004-04-10 devnull .PP
122 cfa37a7b 2004-04-10 devnull An alternative regular expression,
123 cfa37a7b 2004-04-10 devnull .BR "e0\||\|e1" ,
124 cfa37a7b 2004-04-10 devnull matches either a match to
125 cfa37a7b 2004-04-10 devnull .B e0
126 cfa37a7b 2004-04-10 devnull or a match to
127 cfa37a7b 2004-04-10 devnull .BR e1 .
128 cfa37a7b 2004-04-10 devnull .PP
129 cfa37a7b 2004-04-10 devnull A match to any part of a regular expression
130 cfa37a7b 2004-04-10 devnull extends as far as possible without preventing
131 cfa37a7b 2004-04-10 devnull a match to the remainder of the regular expression.
132 cfa37a7b 2004-04-10 devnull .SH "SEE ALSO"
133 d32deab1 2020-08-16 rsc .MR regexp (3)