In Bash, how do I test if a variable is defined in “-u” mode

Question

I just discovered set -u in bash and it helped me find several previously unseen bugs. But I also have a scenario where I need to test if a variable is defined

Answer 1

Unfortunatly [[ -v variable ]] is not supported in older versions of bash (at least not in version 4.1.5 I have on Debian Squeeze)

You could instead use a sub shell as in this :

if (true $variable)&>/dev/null; then
    variable="$(...)"
fi