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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  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   `[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 explic-
       itly.  (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 regu-
       lar expression `*' means	zero or	more copies of the preceding thing.

       Now that	regular	expressions have bracket expressions where  the	 nega-
       tion 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 collat-
       ing 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  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)

NAME | DESCRIPTION | WILDCARD MATCHING | PATHNAMES | EMPTY LISTS | NOTES | SEE ALSO

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