2 сент. 2016 г. · Most compact way is : ${MY_VARIABLE:?} It will print a message and return with non-0 code if it doesn't exist: -bash: MY_VARIABLE: parameter null or not set.

22 мар. 2018 г. · I have a script that has to check whether the environment variable FILE was set but also whether the path to it really exists.

12 мар. 2020 г. · I have a ( #!/usr/bin/env bash ) function that checks for the existence of an (environment) variable checkForVariable() { if [[ -z $1 ]]; then echo "Error: ...

19 нояб. 2016 г. · Use the first; it directly tries to check if something is defined in environ. Though the second form works equally well, it's lacking semantically.

22 сент. 2011 г. · In a bash script, I'm trying to test for the existence of a variable. But no matter what I do, my "if" test returns true.

30 авг. 2010 г. · The right way: if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi where ${var+x} is a parameter expansion which evaluates to

22 июн. 2022 г. · You can use a no-op ( : ): : ${x:?x is empty or not set} ${y:?y is empty or not set}. Or : ${x?x is not set} ${y?y is not set}.

5 янв. 2022 г. · I would like to make it that the script checks if RUN_ENV already exists and activates it instead of forcing its creation every time.

15 дек. 2020 г. · The right way is to check if the environment variable exists by its name, but i cant find a way to do this without knowing how the variable name and hardcoding ...

18 авг. 2022 г. · So the important thing when setting the prompt like this, is that you (probably) want to reevaluate it every time it prints the prompt.