[TUHS] Excise process from a pipe

[Noel Chiappa]

PS: I see I have over-generalized the problem. Doug's original message say "a
process could excise itself from a pipeline". So presumably the initiation
would come from process2 itself, and it would know when it had no
internally-buffered data.

So now we're back to the issue of 'either we need a system call to merge two
pipes into one, or the process has to hang around and turn itself into a cat'.

	Noel