glob - globbing pathnames


   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

   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 '!'.)


   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


   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 '\'.

   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

       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.)


   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

   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 "[a]", that is, to "[a[.a-acute.][.a-grave.][.a-


   sh(1), fnmatch(3), glob(3), locale(7), regex(7)


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