Need help implementing automatic signoff under 4.2 BSD UNIX.

[David E. Miran]

I am planning to implement an automatic signoff feature so that
idle terminals will be signed out after 30 minutes with no activity.
We are running Berkeley 4.2 Unix on a VAX-11/750.
If anyone has already done this or has any useful suggestions please
mail code or suggestions to:
David E. Miran         ...!{seismo,harvard,topaz,ihnp4}!uwvax!uwslh!dem
I want to do this right so that I can correctly kill off those processes
waiting for terminal input, but not those that are waiting for some
other activity to complete (like a slow tape drive on a busy system).
This second requirement means that the scheme used by the w or uptime
program is not sufficient.
I would also want to find and kill off the parent of this process and
repeat until I had killed off the person's login shell, being careful
not to go so far as to kill init.
I have some general ideas on how to modify the kernel to allow this, but
it looks like a lot of work and could hurt system efficiency it it
is done poorly.  Any help would be appreciated.
-- 
David E. Miran         ...!{seismo,harvard,topaz,ihnp4}!uwvax!uwslh!dem
Wisconsin State Hygiene Lab          (608) 262-0019
University of Wisconsin
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Madison, WI  53706