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REGEXP(6)                        Games Manual                        REGEXP(6)

       regexp - regular expression notation

       A  regular expression specifies a set of strings of characters.  A mem-
       ber of this set of strings is said to be matched by the regular expres-
       sion.   In  many  applications a delimiter character, commonly bounds a
       regular expression.  In the following specification for regular expres-
       sions the word `character' means any character (rune) but newline.

       The syntax for a regular expression e0 is

              e3:  literal | charclass | '.' | '^' | '$' | '(' e0 ')'

              e2:  e3
                |  e2 REP

              REP: '*' | '+' | '?'

              e1:  e2
                |  e1 e2

              e0:  e1
                |  e0 '|' e1

       A  literal  is  any  non-metacharacter,  or  a  metacharacter  (one  of
       .*+?[]()|\^$), or the delimiter preceded by

       A charclass is a nonempty string s bracketed [s] (or [^s]); it  matches
       any  character  in  (or  not  in)  s.   A negated character class never
       matches newline.  A substring a-b, with a and  b  in  ascending  order,
       stands  for  the  inclusive range of characters between a and b.  In s,
       the metacharacters an initial and the regular expression delimiter must
       be  preceded  by a other metacharacters have no special meaning and may
       appear unescaped.

       A matches any character.

       A matches the beginning of a line; matches the end of the line.

       The REP operators match zero or more (*), one or more (+), zero or  one
       (?), instances respectively of the preceding regular expression e2.

       A concatenated regular expression, e1e2, matches a match to e1 followed
       by a match to e2.

       An alternative regular expression, e0|e1, matches either a match to  e0
       or a match to e1.

       A  match to any part of a regular expression extends as far as possible
       without preventing a match to the remainder of the regular expression.

       awk(1), ed(1), sam(1), sed(1), regexp(2)