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From: jpn@teddy.UUCP (John P. Nelson)
Newsgroups: comp.unix.questions
Subject: Re: Fork and Join, Pipe in C
Message-ID: <4146@teddy.UUCP>
Date: Mon, 29-Jun-87 11:08:25 EDT
Article-I.D.: teddy.4146
Posted: Mon Jun 29 11:08:25 1987
Date-Received: Sat, 4-Jul-87 22:43:10 EDT
References: <7737@brl-adm.ARPA> <1186@ius2.cs.cmu.edu> <8174@utzoo.UUCP> <21685@sun.uucp> <113@xyzzy.UUCP> <117@xyzzy.UUCP>
Reply-To: jpn@teddy.UUCP (John P. Nelson)
Organization: GenRad, Inc., Concord, Mass.
Lines: 23

>There is a close analogy to fork(), exec(), and create_process() in
>link(), unlink(), and rename(). ... some extra efficency can be added
>by hinting to the kernel that an unlink() will follow the link()
>(avoiding the necessity to change the link count and so on) by
>introducing the system call vlink().

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]);

Unless create_process allows for modification of the file descriptors, it will
be of limited utility.