Async pipes under SYS3,SYS5

[paul at hp-lsd.UUCP]

Nf-From: hp-lsd!paul    Jul 24 10:16:00 1984


The basic win with named pipes (or FIFO's) is that you can connect unrelated
processes with pipes.  GWYN at BRL gave a good general use for them and I can
add a couple more along the same lines:

	Games: Now you can have your "gamesmaster" (database keeper?)
		run all the time and just connect to it when playing is
		convenient.

	(More seriously - any global database managing program can be wired
	 this way)

	Message-based systems can be implemented (somewhat) if you remember
	that writes to pipes of 4K or less (a safe value I think on seeing
	various unices) are atomic.  This means that if you separate your
	writes to the pipes (ie.. length followed by data) you can read
	from several processes at once on one channel (nice since you don't
	have select() in SYS-III).  [This is a good way to tell the
	gamesmaster that you want to play now - and can potentially handle all
	the input from the various simultaneous players].  For message-based
	systems, it is probably nice to have a publicly known "mailbox"
	(or named pipe) connected to a name server for finding out who 
	else is "out there".

	As mentioned, line printer spoolers are a good application as well
	as most any time you want to arbitrate one resource with a program
	(even a network connection?).


			--Paul Bame
			HP Logic Systems Division - Colorado Springs
			{ihnp4!hpfcla, hplabs} !hp-lsd!paul