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 afterward 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  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 "[--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 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 ar-
       chive 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 using this
       command:

	   shopt -s nullglob

       (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: 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 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 items 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 current 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 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 "[aaaaa]", 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 3.53 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								    2012-07-28								   GLOB(7)