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 1003.2, 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 pat-
       tern 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  charac-
       ters  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  `[ABCDE-
       Fabcdef0123456789]'.)   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 `[--/]' matches the three characters `-', `.', `/'.)

   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 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 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 behaviour 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 filenames,  rather  than
       text, and secondly, the conventions are not the same: e.g., 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 let-
       ter".   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 regular expressions.  In the above we saw three types of item  that	can  occur  in	a  bracket
       expression:  namely  (i) the negation, (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 currect collating sequence as defined by the  LC_COL-
       LATE 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  cur-
       rent 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 current locale. For example, `[[=a=]]' might be equivalent to `[aaaaa]' (warning:  Latin-1  here),  that  is,	to
       `[a[.a-acute.][.a-grave.][.a-umlaut.][.a-circumflex.]]'.

SEE ALSO

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

Unix								    1998-06-12								   GLOB(7)