***  Filename Generation

  Following substitution, each command word is scanned for the characters *
  (asterisk), ? (question mark), and [ ] (brackets), unless the -f option was
  set.  If one of these characters appears, the word is regarded as a pat-
  tern.  The word is replaced with lexicographically sorted filenames that
  match the pattern.  If no filename is found that matches the pattern, the
  word is left unchanged.  When a pattern is used for filename generation,
  the . (dot) character at the start of a filename or immediately following a
  / (slash), as well as the / character itself, must be matched explicitly.
  In other instances of pattern matching, the / and . are not treated spe-
  cially.

  *   Matches any string, including the null string.

  ?   Matches any single character.

  [...]
      Matches any one of the enclosed characters.  In an expression such as
      [a-z], the - (dash) means "through" according to the current collating
      sequence.  The collating sequence is determined by the value of the
      LC_COLLATE environment variable.  If the first character following the
      [  (left bracket) is a ! (exclamation point), then any character not
      enclosed is matched.  A - can be included in the character set by put-
      ting it as the first or last character.

  A pattern_list is a list of one or more patterns separated from each other
  with a | (vertical bar).  Composite patterns can be formed with one or more
  of the following:

  ?(pattern_list)
      Optionally matches any one 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 exactly one of the given patterns.

  !(pattern_list)
      Matches anything, except one of the given patterns.

  Character Classes

  You can use the following notation to match filenames within a range indi-
  cation:

       [:charclass:]

  This format instructs the system to match any single character belonging to
  charclass; the defined classes correspond to ctype() subroutines as fol-
  lows:

       alnum
       alpha
       cntrl
       digit
       graph
       lower
       print
       punct
       space
       upper
       xdigit

  Your locale might define additional character properties, such as the fol-
  lowing:

       [:vowel:]

  The preceding character class could be TRUE for a, e, i, o, u, or y.  You
  could then use [:vowel] inside a set construction to match any vowel.
  Refer to The LC_CTYPE Category section of the locale file format reference
  page for more information.