File: gawk.info,  Node: Regexp Summary,  Prev: Case-sensitivity,  Up: Regexp

3.9 Summary
===========

   * Regular expressions describe sets of strings to be matched.  In
     'awk', regular expression constants are written enclosed between
     slashes: '/'...'/'.

   * Regexp constants may be used standalone in patterns and in
     conditional expressions, or as part of matching expressions using
     the '~' and '!~' operators.

   * Escape sequences let you represent nonprintable characters and also
     let you represent regexp metacharacters as literal characters to be
     matched.

   * Regexp operators provide grouping, alternation, and repetition.

   * Bracket expressions give you a shorthand for specifying sets of
     characters that can match at a particular point in a regexp.
     Within bracket expressions, POSIX character classes let you specify
     certain groups of characters in a locale-independent fashion.

   * Regular expressions match the leftmost longest text in the string
     being matched.  This matters for cases where you need to know the
     extent of the match, such as for text substitution and when the
     record separator is a regexp.

   * Matching expressions may use dynamic regexps (i.e., string values
     treated as regular expressions).

   * 'gawk''s 'IGNORECASE' variable lets you control the case
     sensitivity of regexp matching.  In other 'awk' versions, use
     'tolower()' or 'toupper()'.