1 78e51a8c 2005-01-14 devnull .TH REGEXP9 7
  2 78e51a8c 2005-01-14 devnull .SH NAME
  3 78e51a8c 2005-01-14 devnull regexp \- Plan 9 regular expression notation
  4 78e51a8c 2005-01-14 devnull .SH DESCRIPTION
  5 78e51a8c 2005-01-14 devnull This manual page describes the regular expression
  6 78e51a8c 2005-01-14 devnull syntax used by the Plan 9 regular expression library
  7 78e51a8c 2005-01-14 devnull .IR regexp9 (3).
  8 78e51a8c 2005-01-14 devnull It is the form used by
  9 78e51a8c 2005-01-14 devnull .IR egrep (1)
 10 78e51a8c 2005-01-14 devnull before
 11 78e51a8c 2005-01-14 devnull .I egrep
 12 78e51a8c 2005-01-14 devnull got complicated.
 13 78e51a8c 2005-01-14 devnull .PP
 14 78e51a8c 2005-01-14 devnull A 
 15 78e51a8c 2005-01-14 devnull .I "regular expression"
 16 78e51a8c 2005-01-14 devnull specifies
 17 78e51a8c 2005-01-14 devnull a set of strings of characters.
 18 78e51a8c 2005-01-14 devnull A member of this set of strings is said to be
 19 78e51a8c 2005-01-14 devnull .I matched
 20 78e51a8c 2005-01-14 devnull by the regular expression.  In many applications
 21 78e51a8c 2005-01-14 devnull a delimiter character, commonly
 22 78e51a8c 2005-01-14 devnull .LR / ,
 23 78e51a8c 2005-01-14 devnull bounds a regular expression.
 24 78e51a8c 2005-01-14 devnull In the following specification for regular expressions
 25 78e51a8c 2005-01-14 devnull the word `character' means any character (rune) but newline.
 26 78e51a8c 2005-01-14 devnull .PP
 27 78e51a8c 2005-01-14 devnull The syntax for a regular expression
 28 78e51a8c 2005-01-14 devnull .B e0
 29 78e51a8c 2005-01-14 devnull is
 30 78e51a8c 2005-01-14 devnull .IP
 31 78e51a8c 2005-01-14 devnull .EX
 32 78e51a8c 2005-01-14 devnull e3:  literal | charclass | '.' | '^' | '$' | '(' e0 ')'
 33 78e51a8c 2005-01-14 devnull 
 34 78e51a8c 2005-01-14 devnull e2:  e3
 35 78e51a8c 2005-01-14 devnull   |  e2 REP
 36 78e51a8c 2005-01-14 devnull 
 37 78e51a8c 2005-01-14 devnull REP: '*' | '+' | '?'
 38 78e51a8c 2005-01-14 devnull 
 39 78e51a8c 2005-01-14 devnull e1:  e2
 40 78e51a8c 2005-01-14 devnull   |  e1 e2
 41 78e51a8c 2005-01-14 devnull 
 42 78e51a8c 2005-01-14 devnull e0:  e1
 43 78e51a8c 2005-01-14 devnull   |  e0 '|' e1
 44 78e51a8c 2005-01-14 devnull .EE
 45 78e51a8c 2005-01-14 devnull .PP
 46 78e51a8c 2005-01-14 devnull A
 47 78e51a8c 2005-01-14 devnull .B literal
 48 78e51a8c 2005-01-14 devnull is any non-metacharacter, or a metacharacter
 49 78e51a8c 2005-01-14 devnull (one of
 50 78e51a8c 2005-01-14 devnull .BR .*+?[]()|\e^$ ),
 51 78e51a8c 2005-01-14 devnull or the delimiter
 52 78e51a8c 2005-01-14 devnull preceded by 
 53 78e51a8c 2005-01-14 devnull .LR \e .
 54 78e51a8c 2005-01-14 devnull .PP
 55 78e51a8c 2005-01-14 devnull A
 56 78e51a8c 2005-01-14 devnull .B charclass
 57 78e51a8c 2005-01-14 devnull is a nonempty string
 58 78e51a8c 2005-01-14 devnull .I s
 59 78e51a8c 2005-01-14 devnull bracketed
 60 78e51a8c 2005-01-14 devnull .BI [ \|s\| ]
 61 78e51a8c 2005-01-14 devnull (or
 62 78e51a8c 2005-01-14 devnull .BI [^ s\| ]\fR);
 63 78e51a8c 2005-01-14 devnull it matches any character in (or not in)
 64 78e51a8c 2005-01-14 devnull .IR s .
 65 78e51a8c 2005-01-14 devnull A negated character class never
 66 78e51a8c 2005-01-14 devnull matches newline.
 67 78e51a8c 2005-01-14 devnull A substring 
 68 78e51a8c 2005-01-14 devnull .IB a - b\f1,
 69 78e51a8c 2005-01-14 devnull with
 70 78e51a8c 2005-01-14 devnull .I a
 71 78e51a8c 2005-01-14 devnull and
 72 78e51a8c 2005-01-14 devnull .I b
 73 78e51a8c 2005-01-14 devnull in ascending
 74 78e51a8c 2005-01-14 devnull order, stands for the inclusive
 75 78e51a8c 2005-01-14 devnull range of
 76 78e51a8c 2005-01-14 devnull characters between
 77 78e51a8c 2005-01-14 devnull .I a
 78 78e51a8c 2005-01-14 devnull and
 79 78e51a8c 2005-01-14 devnull .IR b .
 80 78e51a8c 2005-01-14 devnull In 
 81 78e51a8c 2005-01-14 devnull .IR s ,
 82 78e51a8c 2005-01-14 devnull the metacharacters
 83 78e51a8c 2005-01-14 devnull .LR - ,
 84 78e51a8c 2005-01-14 devnull .LR ] ,
 85 78e51a8c 2005-01-14 devnull an initial
 86 78e51a8c 2005-01-14 devnull .LR ^ ,
 87 78e51a8c 2005-01-14 devnull and the regular expression delimiter
 88 78e51a8c 2005-01-14 devnull must be preceded by a
 89 78e51a8c 2005-01-14 devnull .LR \e ;
 90 78e51a8c 2005-01-14 devnull other metacharacters 
 91 78e51a8c 2005-01-14 devnull have no special meaning and
 92 78e51a8c 2005-01-14 devnull may appear unescaped.
 93 78e51a8c 2005-01-14 devnull .PP
 94 78e51a8c 2005-01-14 devnull A 
 95 78e51a8c 2005-01-14 devnull .L .
 96 78e51a8c 2005-01-14 devnull matches any character.
 97 78e51a8c 2005-01-14 devnull .PP
 98 78e51a8c 2005-01-14 devnull A
 99 78e51a8c 2005-01-14 devnull .L ^
100 78e51a8c 2005-01-14 devnull matches the beginning of a line;
101 78e51a8c 2005-01-14 devnull .L $
102 78e51a8c 2005-01-14 devnull matches the end of the line.
103 78e51a8c 2005-01-14 devnull .PP
104 78e51a8c 2005-01-14 devnull The 
105 78e51a8c 2005-01-14 devnull .B REP
106 78e51a8c 2005-01-14 devnull operators match zero or more
107 78e51a8c 2005-01-14 devnull .RB ( * ),
108 78e51a8c 2005-01-14 devnull one or more
109 78e51a8c 2005-01-14 devnull .RB ( + ),
110 78e51a8c 2005-01-14 devnull zero or one
111 78e51a8c 2005-01-14 devnull .RB ( ? ),
112 78e51a8c 2005-01-14 devnull instances respectively of the preceding regular expression 
113 78e51a8c 2005-01-14 devnull .BR e2 .
114 78e51a8c 2005-01-14 devnull .PP
115 78e51a8c 2005-01-14 devnull A concatenated regular expression,
116 78e51a8c 2005-01-14 devnull .BR "e1\|e2" ,
117 78e51a8c 2005-01-14 devnull matches a match to 
118 78e51a8c 2005-01-14 devnull .B e1
119 78e51a8c 2005-01-14 devnull followed by a match to
120 78e51a8c 2005-01-14 devnull .BR e2 .
121 78e51a8c 2005-01-14 devnull .PP
122 78e51a8c 2005-01-14 devnull An alternative regular expression,
123 78e51a8c 2005-01-14 devnull .BR "e0\||\|e1" ,
124 78e51a8c 2005-01-14 devnull matches either a match to
125 78e51a8c 2005-01-14 devnull .B e0
126 78e51a8c 2005-01-14 devnull or a match to
127 78e51a8c 2005-01-14 devnull .BR e1 .
128 78e51a8c 2005-01-14 devnull .PP
129 78e51a8c 2005-01-14 devnull A match to any part of a regular expression
130 78e51a8c 2005-01-14 devnull extends as far as possible without preventing
131 78e51a8c 2005-01-14 devnull a match to the remainder of the regular expression.
132 78e51a8c 2005-01-14 devnull .SH "SEE ALSO
133 78e51a8c 2005-01-14 devnull .IR regexp9 (3)