(gawk.info)Regexp


Regular Expressions
*******************

   A "regular expression", or "regexp", is a way of describing a set of
strings.  Because regular expressions are such a fundamental part of
`awk' programming, their format and use deserve a separate major node.

   A regular expression enclosed in slashes (`/') is an `awk' pattern
that matches every input record whose text belongs to that set.  The
simplest regular expression is a sequence of letters, numbers, or both.
Such a regexp matches any string that contains that sequence.  Thus,
the regexp `foo' matches any string containing `foo'.  Therefore, the
pattern `/foo/' matches any input record containing the three
characters `foo' _anywhere_ in the record.  Other kinds of regexps let
you specify more complicated classes of strings.

Regexp Usage: How to Use Regular Expressions.
Escape Sequences: How to write non-printing characters.
Regexp Operators: Regular Expression Operators.
Character Lists: What can go between `[...]'.
GNU Regexp Operators: Operators specific to GNU software.
Case-sensitivity: How to do case-insensitive matching.
Leftmost Longest: How much text matches.
Computed Regexps: Using Dynamic Regexps.

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