12 .if n .RB ` \\$1 '\\$2
20 regexp9 \- Plan 9 regular expression notation
22 This manual page describes the regular expression
23 syntax used by the Plan 9 regular expression library
25 It is the form used by
32 .I "regular expression"
34 a set of strings of characters.
35 A member of this set of strings is said to be
37 by the regular expression. In many applications
38 a delimiter character, commonly
40 bounds a regular expression.
41 In the following specification for regular expressions
42 the word `character' means any character (rune) but newline.
44 The syntax for a regular expression
49 e3: literal | charclass | '.' | '^' | '$' | '(' e0 ')'
65 is any non-metacharacter, or a metacharacter
80 it matches any character in (or not in)
82 A negated character class never
91 order, stands for the inclusive
104 and the regular expression delimiter
105 must be preceded by a
108 have no special meaning and
109 may appear unescaped.
113 matches any character.
117 matches the beginning of a line;
119 matches the end of the line.
123 operators match zero or more
129 instances respectively of the preceding regular expression
132 A concatenated regular expression,
136 followed by a match to
139 An alternative regular expression,
141 matches either a match to
146 A match to any part of a regular expression
147 extends as far as possible without preventing
148 a match to the remainder of the regular expression.