Info Catalog elisp: Regular Expressions elisp: Regexp Example

elisp: Syntax of Regexps

 
 33.3.1 Syntax of Regular Expressions
 ------------------------------------
 
 Regular expressions have a syntax in which a few characters are special
 constructs and the rest are “ordinary”.  An ordinary character is a
 simple regular expression that matches that character and nothing else.
 The special characters are ‘.’, ‘*’, ‘+’, ‘?’, ‘[’, ‘^’, ‘$’, and ‘\’;
 no new special characters will be defined in the future.  The character
 ‘]’ is special if it ends a character alternative (see later).  The
 character ‘-’ is special inside a character alternative.  A ‘[:’ and
 balancing ‘:]’ enclose a character class inside a character alternative.
 Any other character appearing in a regular expression is ordinary,
 unless a ‘\’ precedes it.
 
    For example, ‘f’ is not a special character, so it is ordinary, and
 therefore ‘f’ is a regular expression that matches the string ‘f’ and no
 other string.  (It does _not_ match the string ‘fg’, but it does match a
 _part_ of that string.)  Likewise, ‘o’ is a regular expression that
 matches only ‘o’.
 
    Any two regular expressions A and B can be concatenated.  The result
 is a regular expression that matches a string if A matches some amount
 of the beginning of that string and B matches the rest of the string.
 
    As a simple example, we can concatenate the regular expressions ‘f’
 and ‘o’ to get the regular expression ‘fo’, which matches only the
 string ‘fo’.  Still trivial.  To do something more powerful, you need to
 use one of the special regular expression constructs.
 

Menu

 
· Regexp Special      Special characters in regular expressions.
· Char Classes        Character classes used in regular expressions.
· Regexp Backslash    Backslash-sequences in regular expressions.
 

Info Catalog elisp: Regular Expressions elisp: Regexp Example