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Yes there is a similar thread here:
Test if a variable is set in bash when using "set -o nounset"
However there are so many different answers that it's not particularly clear.
Would the following be sufficient to test if a variable is set AND not empty?
#!/bin/bash
set -o nounset
if [[ ! -z "${EXAMPLE-}" ]]; then
echo "Variable is defined and is not empty..."
Yes, [[ ! -z "${EXAMPLE-}" ]] safely determines whether the variable named EXAMPLE has a non-empty value assigned, even with set -u active.
Personally, I would write [[ -n "${EXAMPLE-}" ]] or even [[ ${EXAMPLE-} ]] -- taking advantage of additional terseness made safe by [[ ]] and not trustworthy with [ ] -- but all these are correct.
You can use the -v operator to check if a name has been set to a value:
if [[ -v EXAMPLE ]]; then
echo "Safe to expand: $EXAMPLE"
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