(grep.info.gz) Regular Expressions
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3 Regular Expressions
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A "regular expression" is a pattern that describes a set of strings.
Regular expressions are constructed analogously to arithmetic
expressions, by using various operators to combine smaller expressions.
`grep' understands three different versions of regular expression
syntax: "basic," (BRE) "extended" (ERE) and "perl". In GNU `grep',
there is no difference in available functionality between the basic and
extended syntaxes. In other implementations, basic regular expressions
are less powerful. The following description applies to extended
regular expressions; differences for basic regular expressions are
summarized afterwards. Perl regular expressions give additional
functionality, and are documented in the pcresyntax(3) and
pcrepattern(3) manual pages, but may not be available on every system.
Menu
* Fundamental Structure
* Character Classes and Bracket Expressions
* The Backslash Character and Special Expressions
* Anchoring
* Back-references and Subexpressions
* Basic vs Extended
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