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GLOB(7)                    Linux Programmer's Manual                   GLOB(7)

       glob - Globbing pathnames

       Long ago, in Unix V6, there was a program /etc/glob that would expand wildcard pat-
       terns.  Soon afterwards this became a shell built-in.

       These days there is also a library routine glob(3) that will perform this  function
       for a user program.

       The rules are as follows (POSIX.2, 3.13).

   Wildcard Matching
       A  string  is  a  wildcard pattern if it contains one of the characters '?', '*' or
       '['.  Globbing is the operation that expands a wildcard pattern into  the  list  of
       pathnames matching the pattern.  Matching is defined by:

       A '?' (not between brackets) matches any single character.

       A '*' (not between brackets) matches any string, including the empty string.

       Character classes

       An expression "[...]" where the first character after the leading '[' is not an '!'
       matches a single character, namely any of the characters enclosed by the  brackets.
       The  string  enclosed by the brackets cannot be empty; therefore ']' can be allowed
       between the brackets, provided that it is  the  first  character.   (Thus,  "[][!]"
       matches the three characters '[', ']' and '!'.)


       There  is  one  special convention: two characters separated by '-' denote a range.
       (Thus, "[A-Fa-f0-9]" is equivalent to "[ABCDEFabcdef0123456789]".)  One may include
       '-'  in  its  literal  meaning by making it the first or last character between the
       brackets.  (Thus, "[]-]" matches just the two characters ']' and '-',  and  "[--0]"
       matches the three characters '-', '.', '0', since '/' cannot be matched.)


       An expression "[!...]" matches a single character, namely any character that is not
       matched by the expression obtained by removing  the  first  '!'  from  it.   (Thus,
       "[!]a-]" matches any single character except ']', 'a' and '-'.)

       One can remove the special meaning of '?', '*' and '[' by preceding them by a back-
       slash, or, in case this is part of a shell command line, enclosing them in  quotes.
       Between brackets these characters stand for themselves.  Thus, "[[?*\]" matches the
       four characters '[', '?', '*' and '\'.

       Globbing is applied on each of the components of a pathname separately.  A '/' in a
       pathname cannot be matched by a '?' or '*' wildcard, or by a range like "[.-0]".  A
       range cannot contain an explicit '/' character; this would lead to a syntax  error.

       If a filename starts with a '.', this character must be matched explicitly.  (Thus,
       rm * will not remove .profile, and tar c * will not archive all your files; tar c .
       is better.)

   Empty Lists
       The  nice  and simple rule given above: "expand a wildcard pattern into the list of
       matching pathnames" was the original Unix definition.  It allowed one to have  pat-
       terns that expand into an empty list, as in
           xv -wait 0 *.gif *.jpg
       where  perhaps  no  *.gif  files  are present (and this is not an error).  However,
       POSIX requires that a wildcard pattern is left unchanged when it  is  syntactically
       incorrect, or the list of matching pathnames is empty.  With bash one can force the
       classical behavior by setting allow_null_glob_expansion=true.

       (Similar problems occur elsewhere.  E.g., where old scripts have
           rm `find . -name "*~"`
       new scripts require
           rm -f nosuchfile `find . -name "*~"`
       to avoid error messages from rm called with an empty argument list.)

   Regular expressions
       Note that wildcard patterns are not regular expressions, although they  are  a  bit
       similar.   First  of all, they match filenames, rather than text, and secondly, the
       conventions are not the same: for example, in a regular expression '*'  means  zero
       or more copies of the preceding thing.

       Now  that  regular expressions have bracket expressions where the negation is indi-
       cated by a '^', POSIX has declared the effect of a wildcard pattern "[^...]" to  be

   Character classes and Internationalization
       Of  course  ranges were originally meant to be ASCII ranges, so that "[ -%]" stands
       for "[ !"#$%]" and "[a-z]" stands for "any lowercase letter".  Some Unix  implemen-
       tations  generalized this so that a range X-Y stands for the set of characters with
       code between the codes for X and for Y.  However, this requires the  user  to  know
       the character coding in use on the local system, and moreover, is not convenient if
       the collating sequence for the local alphabet differs  from  the  ordering  of  the
       character  codes.  Therefore, POSIX extended the bracket notation greatly, both for
       wildcard patterns and for regular expressions.  In the above we saw three types  of
       items  that  can  occur  in  a  bracket  expression:  namely (i) the negation, (ii)
       explicit single characters, and (iii) ranges.  POSIX specifies ranges in an  inter-
       nationally more useful way and adds three more types:

       (iii)  Ranges  X-Y comprise all characters that fall between X and Y (inclusive) in
       the current collating sequence as defined by the LC_COLLATE category in the current

       (iv) Named character classes, like

       [:alnum:]  [:alpha:]  [:blank:]  [:cntrl:]
       [:digit:]  [:graph:]  [:lower:]  [:print:]
       [:punct:]  [:space:]  [:upper:]  [:xdigit:]

       so  that one can say "[[:lower:]]" instead of "[a-z]", and have things work in Den-
       mark, too, where there are three letters past 'z' in the alphabet.  These character
       classes are defined by the LC_CTYPE category in the current locale.

       (v)  Collating  symbols,  like  "[.ch.]" or "[.a-acute.]", where the string between
       "[." and ".]" is a collating element defined for the  current  locale.   Note  that
       this may be a multi-character element.

       (vi) Equivalence class expressions, like "[=a=]", where the string between "[=" and
       "=]" is any collating element from its equivalence class, as defined for  the  cur-
       rent  locale.   For  example,  "[[=a=]]" might be equivalent to "[a????]" (warning:
       Latin-1 here), that is, to "[a[.a-acute.][.a-grave.][.a-umlaut.][.a-circumflex.]]".

       sh(1), fnmatch(3), glob(3), locale(7), regex(7)

       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-

Linux                             2003-08-24                           GLOB(7)

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