Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!mit-eddie!oberon!castor.usc.edu!blarson
From: blarson@castor.usc.edu (Bob Larson)
Newsgroups: comp.unix.questions
Subject: Re: Fork and Join, Pipe in C
Message-ID: <3128@oberon.USC.EDU>
Date: Tue, 30-Jun-87 16:50:50 EDT
Article-I.D.: oberon.3128
Posted: Tue Jun 30 16:50:50 1987
Date-Received: Thu, 2-Jul-87 01:29:14 EDT
References: <7737@brl-adm.ARPA> <1186@ius2.cs.cmu.edu>
Sender: nobody@oberon.USC.EDU
Reply-To: blarson@castor.usc.edu.UUCP (Bob Larson)
Organization: USC AIS, Los Angeles
Lines: 32

In article <4146@teddy.UUCP> jpn@teddy.UUCP (John P. Nelson) writes:
>The situations are NOT analogous.  One of the most common operations
>done between an fork and an exec is the modifications of the file
>descriptors.  Tell me, with create_process, just how would you create
>an inter-process pipe?  The standard code is:
>
>    pipe(fds)
>    if (fork() == 0)
>	{
>	dup2(fds[1], 1);
>	close(fds[0]);
>	close(fds[1]);
>	exec(...);
>	}
>    close(fds[0]);

On os9, which has the create_process os9fork() call rather than a unix-like
fork (error checking omited for simplicity):

pipe = open("/pipe", S_IREAD | S_IWRITE);
temp = dup(1);
close(1);
dup(pipe);
os9fork(...);
close(1);
dup(temp);
close(temp);

Not much harder than on on unix.
Bob Larson		Arpa: Blarson@Ecla.Usc.Edu
Uucp: {sdcrdcf,seismo!cit-vax}!oberon!castor!blarson
"How well do we use our freedom to choose the illusions we create?" -- Timbuk3