• PCRE regex
  • Meta-characters

  • Meta-characters
  • Meta-characters


    The power of regular expressions comes from the
    ability to include alternatives and repetitions in the pattern.
    These are encoded in the pattern by the use of meta-characters, which do not stand for themselves
    but instead are interpreted in some special way.

    There are two different sets of meta-characters:
    those that are recognized anywhere in the pattern except within
    square brackets, and those that are recognized in square brackets.
    Outside square brackets, the meta-characters are as follows:

    Meta-characters outside square
    Meta-character Description
    \ general escape character with several uses
    ^ assert start of subject (or line, in multiline mode)
    $ assert end of subject or before a terminating newline (or end
    of line, in multiline mode)
    . match any character except newline (by default)
    [ start character class definition
    ] end character class definition
    | start of alternative branch
    ( start subpattern
    ) end subpattern
    ? extends the meaning of (, also 0 or 1 quantifier, also makes
    greedy quantifiers lazy (see repetition)
    * 0 or more quantifier
    + 1 or more quantifier
    { start min/max quantifier
    } end min/max quantifier

    Part of a pattern that is in square brackets is called a character
    . In a character class the only meta-characters are:

    Meta-characters inside square brackets (character classes)
    Meta-character Description
    \ general escape character
    ^ negate the class, but only if the first character
    indicates character range

    The following sections describe the use of each of the