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’, basic and extended regular expressions are merely different
 notations for the same pattern-matching functionality.  In other
 implementations, basic regular expressions are ordinarily less powerful
 than extended, though occasionally it is the other way around.  The
 following description applies to extended regular expressions;
 differences for basic regular expressions are summarized afterwards.
 Perl-compatible regular expressions have different functionality, and
 are documented in the pcre2syntax(3) and pcre2pattern(3) manual pages,
 but work only if PCRE is available in the system.
 

Menu

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

Info Catalog grep: Invoking grep: Top grep: Usage