inserting a register into a shell when it starts

[J. David Boyd]

Any ideas how to do this?

I use a bash shell, with some escape commands to display the process id, etc,
in the title bar of my terminal.

When shelling out from within emacs, I need to reset the PS1 variable so I
don't get junk in my shell window.

I've looked for various hooks that fire when shell starts, but I can't find
anything appropriate.

TIA,

Dave