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I'm trying to read a git config value in a bash script, and conditionally act on it depending on whether it's true or false .

I'd expect to be able to do:

if [ $(git config --get myvalue) ]; then
   echo "True"
   echo "False"
However, when I run the above example, True is always printed. Directly comparing the value to true seems to work properly, like so:
if [ $(git config --get myvalue) = true ]; then
   echo "True"
   echo "False"
However, most programming languages don't require a direct comparison to a boolean value, so this goes against what I'd expect.
It does actually seem like this works:
if $(git config --get myvalue); then
   echo "True"
   echo "False"
My understanding is that putting an expression in [ ] calls the test command under the hood. However, it's not obvious to me why the boolean expression isn't evaluated properly with test.
Why doesn't [ ] evaluate the expression correctly?
                Use get config --type bool --get myvalue to ensure that you actually get a result of true or false, rather than a possible synonym.
– chepner
                Jan 25, 2020 at 14:26
Bash doesn't have boolean variables. true is a string and could be written as "true" or 'true' with no change in semantics. It is normal and correct to explicitly compare it to true or false.
if [[ $(git config --get myvalue) == true ]]; then
   echo "True"
   echo "False"
Don't do this. It's a major security vulnerability. What it's really is doing executing whatever command git config outputs. It happens to work because there are commands named true and false which succeed and fail, respectively.
What if that command weren't true or false? What if somebody were to change myvalue to rm -rf /? You'd be having a bad time...
                Also, --type bool should be passed to ensure that you get back true, rather than possibly yes (which would trigger a false negative for the suggested code and an infinite loop leading to memory exhaustion for the second).
– chepner
                Jan 25, 2020 at 14:27
        
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