glob


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.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   "[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.
           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  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: for example, in a
       regular 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
       letter".   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 cod-
       ing 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.
       sh(1), fnmatch(3), glob(3), locale(7), regex(7)

COLOPHON
       This page is part of release 3.23 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                             2003-08-24                           GLOB(7)
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