Subversion Repositories planix.SVN

Rev

Rev 2 | Details | Compare with Previous | Last modification | View Log | RSS feed

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