A few possible process substitution issues

[Dan Douglas]

Hello,

 1. Process substitution within array indices.

The difference between (( 1<(2) )) and (( a[1<(2)] )) might be seen as 
surprising.
Zsh and ksh don't do this in any arithmetic context AFAICT.

Fun stuff:

        # print "moo"
        dev=fd=1 _[1<(echo moo >&2)]=

        # Fork bomb
        ${dev[${dev='dev[1>(${dev[dev]})]'}]}

 2. EXIT trap doesn't fire when leaving a process substitution.

        $ ksh -c '[[ -n $(< <(trap "tee /dev/fd/3" EXIT)) ]] 3>&1 <<<works || 
echo "fail :("'
        works
        $ zsh -c '[[ -n $(< <(trap "tee /dev/fd/3" EXIT)) ]] 3>&1 <<<works || 
echo "fail :("'
        works
        $ bash -c '[[ -n $(< <(trap "tee /dev/fd/3" EXIT)) ]] 3>&1 <<<works || 
echo "fail :("'
        fail :(

 3. Can't wait on a process substitution.

ksh appears to be able to wait on a process substitution. Bash and Zsh can't,
but I'm not sure why.

        $ ksh -c '{ { : <(sleep 1; printf 1 >&2); } 2>&1; wait $!; printf 2; } 
| cat; echo'
        12
        $ bash -c '{ { : <(sleep 1; printf 1 >&2); } 2>&1; wait $!; printf 2; } 
| cat; echo'
        bash: wait: pid 9027 is not a child of this shell
        21

At least, this is a confusing error, because that actually is a direct child
of the shell that runs the wait. Process substitutions do set $! in Bash, not 
in Zsh.

-- 
Dan Douglas