glob(7)



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 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 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 "[--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 explic-
       itly.   (Thus,  rm * will not remove .profile, and tar c * will not ar-
       chive 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 com-
       mand:

           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
   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  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
       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  cod-
       ing  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_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
       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 "[aaaaa]", 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 4.15 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
       https://www.kernel.org/doc/man-pages/.

Linux                             2016-10-08                           GLOB(7)

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