how do you time-out on a read?

[Ken Poulton]

I am considering putting up a Ratfor implementation of MMDF
on several machines, including various flavors of Unix.
MMDF requires that you be able to time-out on a read request,
i.e., that the read returns (with or without data) after some
time limit has elapsed.

Some perusing of manuals (4.1) has not shed any light on this
for me.  Does anyone know of a way?

The ideal method would allow a call to simply set a time-out
interval on an i/o channel, which would be observed until changed,
but I'm open to any working solution.
Since this needs to runs on both Berkeley and Bell Unices,
the less fancy stuff needed, the better.

                              Much thanks,
                              Ken Poulton
                              ...!hplabs!kdp