How do I get `__FILE__` when sourcing a csh script

If you access $_ on the first line of the file, it will contain the name of the file if it's sourced. If it's run directly then $0 will contain the name.

#!/bin/tcsh
set called=($_)
if ($called[2] != "") echo "Sourced: $called[2]"
if ($0 != "tcsh") echo "Called: $0"

This is hard to read, but is actually works:

If your script is named test.csh

/usr/sbin/lsof +p $$ | \grep -oE /.\*test.csh