Thanks for the response, but as you indicate at the end of your post, it only works when a and b are in the same directory. My useCase has to address the notion that a is in a different directory and not necessarily always a.

The useCase is that /app1/a.sh sources /common/b.sh
/app2/c.sh sources /common/b.sh

I need b.sh to know that he is in the common directory.