glob(7) — Linux manual page

NAME | DESCRIPTION | NOTES | SEE ALSO | COLOPHON

GLOB(7)                 Linux Programmer's Manual                GLOB(7)

NAME         top

       glob - globbing pathnames

DESCRIPTION         top

       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         top

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

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.10 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
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Linux                          2020-08-13                        GLOB(7)

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