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



NAME
       glob - Globbing pathnames

DESCRIPTION
       Long  ago,  in Unix V6, there was a program /etc/glob that would expand wildcard patterns.  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 '!'.)

       Ranges

       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.)

       Complementation

       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 backslash, 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 '\'.

   Pathnames
       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 syn-
       tax 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 patterns 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.)

NOTES
   Regular expressions
       Note that wildcard patterns are not regular expressions, although they are a bit similar.  First of all, they match file-
       names,  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 indicated by a '^', POSIX  has  declared  the
       effect of a wildcard pattern "[^...]" to be undefined.

   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 implementations 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 regu-
       lar expressions.  In the above we saw three types of items that can occur in a bracket expression: namely (i)  the  nega-
       tion,  (ii)  explicit  single characters, and (iii) ranges.  POSIX specifies ranges in an internationally 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 locale.

       (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 Denmark, 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 multicharacter element.

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

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

COLOPHON
       This  page  is  part of release 3.25 of the Linux man-pages project.  A description of the project, and information about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2003-08-24                                                    GLOB(7)