gawk: Regexp Summary

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1 3.9 Summary
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1    * Regular expressions describe sets of strings to be matched.  In
1      'awk', regular expression constants are written enclosed between
1      slashes: '/'...'/'.
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1    * Regexp constants may be used standalone in patterns and in
1      conditional expressions, or as part of matching expressions using
1      the '~' and '!~' operators.
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1    * Escape sequences let you represent nonprintable characters and also
1      let you represent regexp metacharacters as literal characters to be
1      matched.
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1    * Regexp operators provide grouping, alternation, and repetition.
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1    * Bracket expressions give you a shorthand for specifying sets of
1      characters that can match at a particular point in a regexp.
1      Within bracket expressions, POSIX character classes let you specify
1      certain groups of characters in a locale-independent fashion.
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1    * Regular expressions match the leftmost longest text in the string
1      being matched.  This matters for cases where you need to know the
1      extent of the match, such as for text substitution and when the
1      record separator is a regexp.
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1    * Matching expressions may use dynamic regexps (i.e., string values
1      treated as regular expressions).
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1    * 'gawk''s 'IGNORECASE' variable lets you control the case
1      sensitivity of regexp matching.  In other 'awk' versions, use
1      'tolower()' or 'toupper()'.
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