gawk: Regexp Summary
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()'.
Info Catalog
gawk: Case-sensitivity
gawk: Regexp