Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
REGEXP(7)	       Miscellaneous Information Manual		     REGEXP(7)

NAME
       regexp -	Plan 9 regular expression notation

DESCRIPTION
       This  manual  page  describes the regular expression syntax used	by the
       Plan 9 regular expression library regexp(3).  It	is the	form  used  by
       egrep(1)	before egrep got complicated.

       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.

SEE ALSO
       regexp(3)

								     REGEXP(7)

NAME | DESCRIPTION | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=regexp&sektion=7&manpath=FreeBSD+12.1-RELEASE+and+Ports>

home | help