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3.5.8.1 Pattern Matching

3.5.8.1 Pattern Matching

• Any character that appears in a pattern, other than the special pattern characters described below, matches itself. The NUL character may not occur in a pattern. A backslash escapes the following character; the escaping backslash is discarded when matching. The special pattern characters must be quoted if they are to be matched literally.
• The special pattern characters have the following meanings:
  • *

    Matches any string, including the null string. When the globstar shell
    option is enabled, and '*' is used in a filename expansion context, two
    adjacent '*'s used as a single pattern will match all files and zero or
    more directories and subdirectories. If followed by a ‘/’, two adjacent
    ‘*’s will match only directories and subdirectories.
            

  • ?

    Matches any single character.
            

  • […]

    Matches any one of the enclosed characters. A pair of characters
    separated by a hyphen denotes a range expression; any character
    that falls between those two characters, inclusive, using the
    current locale’s collating sequence and character set, is matched.
    If the first character following the ‘[’ is a ‘!’ or a ‘^’ then
    any character not enclosed is matched. A ‘-’ may be matched by
    including it as the first or last character in the set. A ‘]’
    may be matched by including it as the first character in the set.
    The sorting order of characters in range expressions is determined
    by the current locale and the values of the LC_COLLATE and LC_ALL
    shell variables, if set.
    
    For example, in the default C locale, ‘[a-dx-z]’ is equivalent
    to ‘[abcdxyz]’. Many locales sort characters in dictionary order,
    and in these locales ‘[a-dx-z]’ is typically not equivalent to ‘[abcdxyz]’;
    it might be equivalent to ‘[aBbCcDdxXyYz]’, for example. To obtain the
    traditional interpretation of ranges in bracket expressions, you can
    force the use of the C locale by setting the LC_COLLATE or LC_ALL
    environment variable to the value ‘C’, or enable theglobasciiranges
    shell option.
    
    Within ‘[’ and ‘]’, character classes can be specified using the
    syntax [:class:], where class is one of the following classes defined in the POSIX standard:
    
    alnum   alpha   ascii   blank   cntrl   digit   graph   lower
    print   punct   space   upper   word    xdigit
    
    A ctharacter class matches any character belonging to that class.
    The word character class matches letters, digits, and the character ‘_’.
    
    Within ‘[’ and ‘]’, an equivalence class can be specified using the
    syntax [=c=], which matches all characters with the same collation
    weight (as defined by the current locale) as the character c.
    
    Within ‘[’ and ‘]’, the syntax [.symbol.] matches the collating symbol symbol.
    
    If the extglob shell option is enabled using the shopt builtin, several
    extended pattern matching operators are recognized. In the following description,
    a pattern-list is a list of one or more patterns separated by a ‘|’. Composite
    patterns may be formed using one or more of the following sub-patterns:
    
            

  • ?(pattern-list)

    Matches zero or one occurrence of the given patterns.
    
            

  • *(pattern-list)

    Matches zero or more occurrences of the given patterns.
            

  • +(pattern-list)

    Matches one or more occurrences of the given patterns.
            

  • @(pattern-list)

    Matches one of the given patterns.
    
            

  • !(pattern-list)

    Matches anything except one of the given patterns.