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RedHat 9 (Linux i386) - man page for glob (redhat section 7)

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 `['. Glob-
       bing 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  char-
       acters `[', `]' 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 `[--/]' matches the three  charac-
       ters `-', `.', `/'.)

   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 charac-
       ters `[', `?', `*' and `\'.

PATHNAMES
       Globbing is applied on each of the components of a pathname separately. A `/' in  a  path-
       name  cannot be matched by a `?' or `*' wildcard, or by a range like `[.-0]'. A range can-
       not 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 bet-
       ter.)

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 letter".  Some Unix implementations general-
       ized 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 cur-
       rect 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 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)


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