I’ve seen a lot of documentation for checking if a variable is set by calling [[ !-z "$VARNAME" ]]. That condictional statement essentially checks to see if the resolved string "$VARNAME" is not an empty string. Not very straight forward is it?
However, I found there is a new (well to me) conditional statement to confirm that the variable is set without all of this. It’s -v.
From the documentation:
`-v varname` > > True if the shell variable varname is set (has been assigned a value). > > [Bash Conditional Expressions (Bash Reference Manual)](https://www.gnu.org/software/bash/manual/html_node/Bash-Conditional-Expressions.html)
Example:
$ [[ -v TEST_VAR ]] && echo "nope"
#(Nothing is shown)
$ export TEST_VAR="asdf"
$ [[ -v TEST_VAR ]] && echo "set var"
set var
Note: Not sure why the formatting is doing that. But the && above should just be &&