reading and writing to another process

[gwyn at brl-vld]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

In general this will be timing-dependent, as the parent process
and the child may get into a deadlock waiting for each other's
communications.  Various solutions work in different situations;
practically all of them involve two pipes and a communications
protocol to avoid deadlock.