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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
       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 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
       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 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]" (warning: Latin-1 here), 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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