Re: Variable in condtion such [[ ${v-} = 9 ]]

[Lawrence Velázquez]

On Mon, Aug 28, 2023, at 1:34 PM, Budi wrote:
> What is variable in condition such
>
>  [[ ${foo-} = bar ]]
>
> as seen in a Linux script of its main package
>
> why is it if just
>  [[ $foo = bar ]]
>
> Please give useful info

The former accommodates foo being unset in a script using set -u,
and the latter doesn't.

        % bash -uc 'unset foo; [[ ${foo-} = bar ]]; echo "$?"'
        1
        % bash -uc 'unset foo; [[ $foo = bar ]]; echo "$?"'   
        bash: line 1: foo: unbound variable

So the script in question uses set -u, or the author was programming
defensively, or the author saw the idiom somewhere and adopted it
without understanding its purpose.

-- 
vq