Provided by: sam_4.3-18.2_i386 bug


        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(7)