Test for a Bash variable being unset, using a function

Question

A simple Bash variable test goes:

${varName:?    \"${varName} is not defined\"}

I\'d like to re-use this, by putting it in a function. How

Answer 1

I don't have understood exactly what do you need. I'm trying to replying you despite of this.

I.e. I need to exit if the test fails.

The code:

${varName:?    "${varName} is not defined"}

will return a non zero exit code when there is not a variable named "varName". The exit code of the last command is saved in $?.

About your code:

val=${1:?    "${1}    must be defined, preferably in $basedir"}

Maybe it is not doing what you need. In the case that $1 is not defined the "${1}" will be substituted with nothing. Probably you want use the single quotes that literally writes ${1} without substitution.

val=${1:?    '${1}    must be defined, preferably in $basedir'