Answer by Dennis Williamson for determining path to sourced shell script

In tcsh, $_ at the beginning of the script will contain the location if the file was sourced and $0 contains it if it was run.

#!/bin/tcsh
set sourced=($_)
if ("$sourced" != "") then
    echo "sourced $sourced[2]"
endif
if ("$0" != "tcsh") then
    echo "run $0"
endif

In Bash:

#!/bin/bash
[[ $0 != $BASH_SOURCE ]] && echo "Script is being sourced" || echo "Script is being run"