I'm confused. I see several references to readlink(1) in the responses to this request, but I didn't see any indication that the file being executed is a symbolic link.

In practice I would expect that $0 in a shell script would be set to an absolute pathname of the script if the script was found by invoking an absolute pathname for the script or if the script was found using a directory (with an absolute pathname) found in $PATH.

Otherwise, I would expect that $PWD/$0 would be an absolute pathname of the script if the shell script was invoked by using a relative pathname on the command line or was found using a directory (with a relative pathname) found in $PATH.

So, at least with the Bourne shell, bash, and ksh, the following should give an absolute pathname of the script if the following is included in the script before it makes any changes to its current working directory:

Code:

case "$0" in
(/*)    script_path="$0" ;;
(*)     script_path="$PWD"/"$0" ;;
esac

When this uses relative paths, the resulting $script_path may include dot and dot-dot components and may also contain unresolved symbolic links. But, it should always give you an absolute path to the file containing the executing script.