Re: bash expansion crap...

[Mike Bird <mgb-debian@yosemite.net>]

On Tuesday 02 October 2007 11:49, Andrew Sackville-West wrote:
> Hey folks, help me out with this...please
>
> andrew@basement:~$ for i in {1..3}; do echo $i; done
> 1
> 2
> 3
> andrew@basement:~$ TEST=3; for i in {1..$TEST}; do echo $i; done
> {1..3}
>
>
> in the first example, its obvious. In the second, $TEST gets replaced
> with 3, but then the {} doesn't get expanded. I'm sure I have to do
> some kind of wacky $({[ type thing, but I'm not able to grok it. any
> ideas?
>
> the purpose is to be able to easily update some loops in a script for
> different numbers of object to iterate over. obvious, I guess.

From man bash:

       Brace expansion is performed before any other expansions, and any char‐
       acters  special to other expansions are preserved in the result.  It is
       strictly textual.  Bash does not apply any syntactic interpretation  to
       the context of the expansion or the text between the braces.

This is not pretty but it works:

       TEST=3; for i in $(eval echo {1..$TEST}); do echo $i; done

--Mike Bird