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From: allbery@ncoast.UUCP
Newsgroups: comp.unix.questions
Subject: Re: Three-way write
Message-ID: <4946@ncoast.UUCP>
Date: Tue, 27-Oct-87 20:44:38 EST
Article-I.D.: ncoast.4946
Posted: Tue Oct 27 20:44:38 1987
Date-Received: Sat, 31-Oct-87 04:32:03 EST
References: <3154@uwmcsd1.UUCP> <15100001@bucc2> <273@ddsw1.UUCP> <2241@sfsup.UUCP>
Reply-To: allbery@ncoast.UUCP (Brandon Allbery)
Followup-To: comp.unix.questions
Organization: Cleveland Public Access UN*X, Cleveland, Oh
Lines: 24

As quoted from <2241@sfsup.UUCP> by mpl@sfsup.UUCP (M.P.Lindner):
+---------------
| In article <273@ddsw1.UUCP>, karl@ddsw1.UUCP writes:
| > In article <15100001@bucc2> brian@bucc2.UUCP writes:
| > >> I'm looking for C source code to a three (or more) way write program.
| > >  I am currently writing such a program. It will only run on SysV, though,
| > >since I am using shared memory.
| > I've posted a up-to 15 user chat program for System III and later (it uses
| > named pipes) to alt.sources a while ago.  It's written for System V, and
| 
| Has anyone ever considered writing a "write" program that writes to ttys?
| Amazingly enough, this is how the two way "write" program does it, and guess
| what?  It's portable!  I know there are certain drawbacks, like each user
+---------------

The purpose of the IPC is to prevent the output of three different users all
being jumbled together; think of it as a "write spooler", that's basically
the idea.  Since there is no way to write to a tty "atomically" (try it!
--and no, O_APPEND doesn't work on character devices), this is the only way
to "spool" tty writes.
-- 
Brandon S. Allbery		     necntc!ncoast!allbery@harvard.harvard.edu
  {{harvard,mit-eddie}!necntc,well!hoptoad,sun!mandrill!hal}!ncoast!allbery
			 "Uncle _who_?" -- Lt. Worf