singleton for script with shebang

[Bradley Asztalos]

I have a simple script, foo.sh::

#!/bin/bash 

echo "start" $$

sleep 10

echo "end" $$

I can run make sure this runs as a singleton with 

sem --fg -u --id lock_id ./foo.sh

But I'm wondering if it is possible to use shebang in this context as in:

-------singleton.sh---------

#!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id

echo "start" $$

sleep 10

echo "end" $$

---------

This does not work. Any ideas here? 

Bradley