glob

GLOB(7)                     Linux Programmer's Manual                    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.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 multi-character 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
       This page is part of release 3.22 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)