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Regular Expressions as Patterns

A regular expression, or regexp, is a way of describing a class of strings. A regular expression enclosed in slashes (`/') is an awk pattern that matches every input record whose text belongs to that class.

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 `foo'. Other kinds of regexps let you specify more complicated classes of strings.

• Regexp Usage: How to Use Regular Expressions
• Regexp Operators: Regular Expression Operators
• Case-sensitivity: How to do case-insensitive matching.

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