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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
       characters '[', ']' 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
       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
       containing an explicit '/' character is syntactically  incorrect.   (POSIX  requires  that
       syntactically incorrect patterns are left unchanged.)

       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
       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_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
       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 "[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

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