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 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 "[--0]" matches the three  charac‐
       ters '-', '.', '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 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 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.  For example, 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 letter".  Some UNIX implementations gen‐
       eralized 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  expres‐
       sions.   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  speci‐
       fies 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‐
       rent 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 mul‐
       ticharacter 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 "[aáàäâ]", 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 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2012-07-28                                    GLOB(7)