> When I considered using the environment to pass information to
> the commands run by tty_relatives() I realized that the list of
> environment variables would probably change, and I don't like
> the idea of changing the argument list for tty_relatives every
> time we do that.  So, instead, let's pass a null-terminated list
> of environment variables to tty_relatives() like this:

On second thought, lets forget that idea.  It makes too much
work to be done by the caller of tty_relatives() when the work
of building the environment could just a well be done in the
tty_relatives function itself.  If the prototype is:

void tty_relatives(char *filepath, char *ttyname, char *username);

Then tty_relatives() has everything it needs to build the
environment strings for USER, TTY, and PATH.

Are any others needed?

Gordon