Regular Expressions (GNU Grep 3.7)
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3 Regular Expressions
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-compatible (PCRE). 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-compatible regular expressions give additional functionality, and are documented in the pcresyntax(3) and pcrepattern(3) manual pages, but work only if PCRE is available in the system.
- Fundamental Structure
- Character Classes and Bracket Expressions
- The Backslash Character and Special Expressions
- Anchoring
- Back-references and Subexpressions
- Basic vs Extended Regular Expressions
- Character Encoding
- Matching Non-ASCII and Non-printable Characters