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GLOB !!!GLOB NAME DESCRIPTION WILDCARD MATCHING PATHNAMES EMPTY LISTS NOTES SEE ALSO ---- !!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 1003.2, 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 `[[--/]' matches the three characters `-', `.', `/'.) __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 behaviour 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: e.g., 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 `[[ ! (iii) Ranges X-Y comprise all characters that fall between X and Y (inclusive) in the currect 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 `[[a !!SEE ALSO sh(1), glob(3), fnmatch(3), locale(7), regex(7) ----
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glob(7)
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Man7g
fnmatch(3)
glob(3)
globfree(3)
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