-v
(in place of [ -n "${var+x}" ]
) is undefined.#!/bin/sh
if [ -v STY ]
then
echo "STY is set, you are using screen"
fi
Either switch to bash:
#!/bin/sh
if [ -n "${STY+x}" ]
then
echo "STY is set, you are using screen"
fi
Your script uses a shell feature not supported by the shebang. Either rewrite the script to be portable, or change the shebang to explicitly require a shell like Bash.
In this case, [ -v variable ]
to check if a variable is set can be replaced with [ -n "${variable+x}" ]
which uses the "alternative value if set" parameter expansion syntax to accomplish the same thing.
None
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.