Question

Is there any way to throw errors or warnings in a KornShell (ksh) script to prevent the use of unset variables? Let’s assume I have a temporary folder that I want to remove.

TEMP_FILES_DIR='/app/myapp/tmp' rm -Rf $TEMP_FILE_DIR #notice the misspelling 

How to prevent this kind of mistakes before they actually happen?

I know the script should check for file existence and empty string before attempting to remove, this is just a silly example to illustrate a mistake that could have been avoided with some warnings. I don’t know if this feature exists in ksh. If it does exist, how do you turn it on?

Answer 1

The command

set -u

Will cause POSIX sh(1) and its derivatives to grouse when an attempt to expand an unset variable is made.

Example:

 $ echo $foo  $ set -u $ echo $foo sh: foo: parameter not set