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From Luke Jackson

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	chown 701 public_html/chap{0{8,9},1{0,1,2}}		chown 701 public_html/chap{0{8,9},1{0,1,2}}
	the last token will be expanded to the list: chap08, chap09, chap10, chap11, and chap12 ( the command will attempt to operate on the all the paths, possibly failing on any path that does not exist ). Note that you can nest braces.		the last token will be expanded to the list: chap08, chap09, chap10, chap11, and chap12 ( the command will attempt to operate on the all the paths, possibly failing on any path that does not exist ). Note that you can nest braces.
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Revision as of 17:14, 29 September 2007

Globbing

Globbing is the name for the shell's filename expansion capabilities. When the shell parses a command line, it looks in each token ( word, if you like ) for the special characters:

•  ? - One of any character
• * - Zero or more of any character
• [ - Introduces a character class

If it finds any of these, it replaces token with a list of all filenames that match the pattern that the token represents. The ? character is a wild card that stands for 'one of any character' -- except the dot ( . ). It must match one character: 'abc?' does not match 'abc', but does match 'abcd'. The * character matches zero or more of any character. The pattern 'abc*' matches 'abc' as well as 'abcd' and 'abcdefgh...'. The [ character introduces a character class, a list of single characters that can be matched. The pattern 'abc[de]' matches 'abcd' and 'abce' but not 'abc' nor 'abcg'. If no match is found, the meta characters can be taken as literally what the are. If you do not want a meta character expanded, you need to escape it with a backslash, e.g., a file named 'abc*' would have to be typed 'abc\*' to avoid expansion. The best way to avoid problems, though, is to avoid special characters -- don't use anything in a filename that you have to escape.

Brace Expansion

On a similar subject, the shell also does brace expansion ( which is not globbing -- globbing is done to names from the filesystem ). If it sees a { character in a token, it checks to see if there is a pair of braces containing a properly formatted list of text strings ( at least one comma and no spaces ) then generates a list of tokens from the expansions. Note well that it does not do filename matching in order to determine whether to generate the token. Given the command

chown 701 public_html/chap{0{8,9},1{0,1,2}}

the last token will be expanded to the list: chap08, chap09, chap10, chap11, and chap12 ( the command will attempt to operate on the all the paths, possibly failing on any path that does not exist ). Note that you can nest braces.