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

In the beginning of your script, you could define your variables with an empty value

variable_undefined=""

Then

if [ "${variable_undefined}" == "" ]; then
    variable="$(...)"
fi