What does ${VARIABLE+x} mean in bash? [duplicate]

Question

I've come across code that uses this syntax in an if condition:

if [ ! -z ${VARIABLE+x} ]; then
    some commands here
fi

Does it test for an non-empty variable? If so, how is it different from ! -z "$VARIABLE"?

I would, as that would be plagiarism :-) I'm just saying that answer pretty much answers your question. — Oldskool
– Oldskool, Commented Feb 22, 2018 at 12:14

Heath Borders · Accepted Answer · 2024-04-24 19:14:06Z

13

${parameter:+word}

Use Alternate Value. If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted.

And few paragraphs above in the same section:

Omitting the colon results in a test only for a parameter that is unset.

Heath Borders

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answered Feb 22, 2018 at 12:06

choroba

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