Let us be very clear here. When doing tests like this with a shell script, sometimes you have to know what shell you're using. Claiming that cd -P can't be used in /bin/sh might or might not be true. If you're using a Linux system where /bin/sh is a link to bash, you can use cd -P. If you're using a Solaris system where /bin/sh is a legacy Bourne shell, you can't use cd -P, but you can't use $(command) either (you'd have to use `command` instead).

Furthermore, the awk script shown in the code above is going to return an empty string any time $0 expands to an absolute pathname for the script being executed and . otherwise. That is the basis of the problem that kept the script from doing what the submitter intended to do. But..., as has been said before, I'm not sure that I understand this thread. If someone copies a script and slightly modifies it for some reason (any reason), modifying the original script to see if it has been moved doesn't help. Anybody that can copy and modify the script can obviously and easily also remove any code that verifies that the script hasn't been moved or modified.