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GLOB(7) | Linux Programmer's Manual | GLOB(7) |
NAME¶
glob - globbing pathnamesDESCRIPTION¶
Long ago, in UNIX V6, there was a program /etc/glob that would expand wildcard patterns. Soon afterward this became a shell built-in.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: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.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 inxv -wait 0 *.gif *.jpg
shopt -s nullglob
rm `find . -name "*~"`
rm -f nosuchfile `find . -name "*~"`
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.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:[: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.
SEE ALSO¶
sh(1), fnmatch(3), glob(3), locale(7), regex(7)COLOPHON¶
This page is part of release 3.44 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/.2012-07-28 | Linux |