Info Catalog grep: Invoking grep: Top grep: Usage

grep: Regular Expressions

 
 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.
 

Menu

 
· Fundamental Structure
· Character Classes and Bracket Expressions
· The Backslash Character and Special Expressions
· Anchoring
· Back-references and Subexpressions
· Basic vs Extended
· Character Encoding
· Matching Non-ASCII
 

Info Catalog grep: Invoking grep: Top grep: Usage