bash function fails with set -e

Question

I have discovered some strange behavior when using set -e . A simple code: [ ${var} } && echo "text" works fine outside a function but causes the script to exit when the same code is in a function. This only occurs if var="" .

The code also works fine if I use ||or if I set the var to something. Has anybody got an explanation for this?

#!/bin/bash
#version 4.4.20(1)
#set -x
set -e
var=
[ ${var} ] && echo "Test before function"
echo "Before function"
function test {
    [ ${var} ] && echo "Test inside function"
}

test
echo end

Answer 1

Consider the following:

• false && true exits with exit status false .

• The default return value of a function is the return value of the last thing it ran.

• set -e is defined to cause early termination if any unchecked command ("unchecked" being a word which, in this context, has a complex, caveat-filled, version-dependent, nonportable, and otherwise often-surprising definition) returns an exit status other than true.

Thus, when you have a function that runs a-false-thing && a-true-thing as its last command before returning, the function itself will return false, and set -e will terminate execution if it considers the function's invocation "checked".