Re: Which is faster `[[ -v x[k] ]]` vs `[[ ${x[k]} ]]`?

[Stephane Chazelas]

2019-10-27 18:58:22 -0500, Peng Yu:
[...]
> I am confused about which one is faster `[[ -v x[k] ]]` vs `[[ ${x[k]}
> ]]`. Depending on how long it runs, it seems the runtime comparison
> results are different. Why? Which one is supposed to be faster?
[...]

They're not functionaly equivalent.

[[ -v x[k] ]] tests whether the x sparse array has an element
for key k, [[ ${x[k]} ]] tests whether ${x[k]} expands to a
non-empty string (for which you need the x sparse array to have
an element for key k and that element being non-empty).

$ x[12]= k=12
$ [[ -v x[k] ]] && echo yes
yes
$ [[ ${x[k]} ]] || echo no
no

-- 
Stephane