Re: for loop over parameter expansion of array can miss resulted empty list

[Greg Wooledge]

On Mon, Mar 21, 2022 at 02:47:12PM -0400, Lawrence Velázquez wrote:
> On Mon, Mar 21, 2022, at 8:50 AM, Alexey via Bug reports for the GNU Bourne 
> Again SHell wrote:
> > I can add one more example, which change array size while it's not 
> > expected behavior:
> > x=("/"); y=("${x[@]%/}"); echo "x size: ${#x[@]}, y size: ${#y[@]}"
> 
> This discrepancy seems to have been introduced some ways back.
> 
> <larryv> 3# echo "$BASH_VERSION"; x=("/"); y=("${x[@]%/}"); echo "x ${#x[@]}, 
> y ${#y[@]}"
> <shbot> 3.2.48(1)-release
> <shbot> x 1, y 1
> <larryv> 42# echo "$BASH_VERSION"; x=("/"); y=("${x[@]%/}"); echo "x 
> ${#x[@]}, y ${#y[@]}"
> <shbot> 4.2.45(1)-release
> <shbot> x 1, y 0

Good point.  The behavior definitely changed between 4.1 and 4.2.

unicorn:~$ bash-3.2 -c 'x=("/"); for i in "${x[@]%/}"; do echo "i is [$i]"; 
done'
i is []
unicorn:~$ bash-4.0 -c 'x=("/"); for i in "${x[@]%/}"; do echo "i is [$i]"; 
done'
i is []
unicorn:~$ bash-4.1 -c 'x=("/"); for i in "${x[@]%/}"; do echo "i is [$i]"; 
done'
i is []
unicorn:~$ bash-4.2 -c 'x=("/"); for i in "${x[@]%/}"; do echo "i is [$i]"; 
done'
unicorn:~$