brace expansion in array subscript

brace expansion in array subscript

[Rory Mulvaney]

Hi,

I'm wondering if it's possible to somehow specify a set of indices to an 
array using brace expansion, to get a subset of the indices?  To get 
indices 2 and 5 of the array "arr", I'd like to use something like:

arr=( elt1 elt2 elt3 elt4 elt5 elt6 ) 
echo ${arr[{2,5}]}

Why doesn't that get expanded into "echo ${arr[2]} ${arr[5]}"?

It seems there would be lots of convenient uses of this feature.

Thanks in advance,
Rory

Re: brace expansion in array subscript

[Bart Schaefer]

On Jul 27,  2:57pm, Rory Mulvaney wrote:
}
} echo ${arr[{2,5}]}
} 
} Why doesn't that get expanded into "echo ${arr[2]} ${arr[5]}"?

Array subscripts are already a comma-separated pair of arithmetic
expressions (or a quoted string value for associative arrays), and
curly braces already have their own special meaning in parameter
expansion expressions.  The syntax for brace expansion doesn't fit
well here.

} It seems there would be lots of convenient uses of this feature.

If you really need it, you can get it this way:

    echo ${(e):-\${arr[{2,5}]}}