glob (7)

NAME

       glob - Globbing pathnames

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 1003.2, 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 pat-
       tern  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 `[--/]' matches
       the three characters `-', `.', `/'.)

   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 `\'.

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  behaviour  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: e.g., in a regu-
       lar 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 let-
       ter".  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 collat-
       ing 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  item 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 currect 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
       class,  as defined for the current locale. For example, `[[=a=]]' might
       be equivalent to `[a

Unix                              1998-06-12                           glob(7)