I have a question after reading about extended glob.
After using shopt -s extglob,
What is the difference in the following?
?(list): Matches zero or one occurrence of the given patterns.
*(list): Matches zero or more occurrences of the given patterns.
+(list): Matches one or more occurrences of the given patterns.
@(list): Matches one of the given patterns.
Yes, I have read the above description that accompanies them, but for practical purpose, I can't see situations where people would prefer ?(list) over *(list). That is, I don't see any difference.
I've tried the following:
$ ls
> test1.in test2.in test1.out test2.out`
$ echo *(*.in)
> test1.in test2.in
$ echo ?(*.in)
> test1.in test2.in
I'd expect $ echo ?(*.in) to output test1.in only, from the description, but it does not appear to be the case. Thus, could anyone give an example where it makes a difference regarding the type of extended glob used?
Source: http://mywiki.wooledge.org/BashGuide/Patterns#Extended_Globs
$ shopt -s extglob
$ ls
abbc abc ac
$ echo a*(b)c
abbc abc ac
$ echo a+(b)c
abbc abc
$ echo a?(b)c
abc ac
$ echo a@(b)c
abc
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