I think you might get what you want with:
exec replaces the current process with a new one described in its arguments
the new command overlays the current shell without spawning a new process.
Since the
pid (
Process Identity does not change then the new command replaces without
remembering the old process, including the
root ID it was running with, everything run from that point on will be the new
user you have named because the
su Set User runs its arguments as
user.
The
- tells
su to set up and run the login sequence.
As
user. The default if no
user is named is
root.
Enjoy your Explorations!