glob(7) - man - phpman

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 '['.  Glob‐
       bing 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  lit‐
       eral  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 in‐
       correct 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  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 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 general‐
       ized  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 alpha‐
       bet 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 internation‐
       ally 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  multicharac‐
       ter 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 ex‐
       ample,  "[[=a=]]" might be equivalent to "[aáaäâ]", 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 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 https://www.kernel.org/doc/man-pages/.



Linux                                        2020-08-13                                      GLOB(7)