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From: steiny@scc.UUCP (Don Steiny)
Newsgroups: net.unix
Subject: #include <sys/mx.h>
Message-ID: <157@scc.UUCP>
Date: Sat, 12-May-84 13:59:57 EDT
Article-I.D.: scc.157
Posted: Sat May 12 13:59:57 1984
Date-Received: Wed, 16-May-84 07:52:23 EDT
Organization: Santa Cruz Computer, Aptos, Calif.
Lines: 22

***

	<sys/mx.h> - is the definations needed for the mpxcall(2)
system call.  V7 "had" this great scheme called multiplexed i/o.
According to the manual, it allowed the user to set up 
interprocess "channels" so that more that processes could
communicate with each other.  There was a special type of file
called a "multiplexed file".  Any number of processes could open the 
file.  "mx.h" contains the definations for the headers and
control messages.

	The catch was, that even though there were manual pages
(see mpx(2), mpxio(4), mx(5) - in the V7 manual), it did not work.
UCB managed to get it to work on 4.1bsd, but it does not work in
regular V7.  UCB has a couple of programs that use it (comsat).

	Code that uses mpx has to be rewritten using messages on System V.

			Don Steiny
			Personetics