From owner-freebsd-stable  Mon Sep  6  8:12:33 1999
Delivered-To: freebsd-stable@freebsd.org
Received: from bingnet2.cc.binghamton.edu (bingnet2.cc.binghamton.edu [128.226.1.18])
	by hub.freebsd.org (Postfix) with ESMTP
	id 24E4B15A6E; Mon,  6 Sep 1999 08:11:49 -0700 (PDT)
	(envelope-from zzhang@cs.binghamton.edu)
Received: from sol.cs.binghamton.edu (cs1-gw.cs.binghamton.edu [128.226.171.72])
	by bingnet2.cc.binghamton.edu (8.9.3/8.9.3) with SMTP id LAA06003;
	Mon, 6 Sep 1999 11:11:38 -0400 (EDT)
Date: Mon, 6 Sep 1999 10:57:50 -0400 (EDT)
From: Zhihui Zhang <zzhang@cs.binghamton.edu>
To: Alex Povolotsky <tarkhil@asteroid.svib.ru>
Cc: stable@FreeBSD.ORG, hackers@FreeBSD.ORG
Subject: Re: Problems with FIFO open in non-blocking mode?
In-Reply-To: <199909060547.JAA29146@shuttle.svib.ru>
Message-ID: <Pine.GSO.3.96.990906105500.13356A-100000@sol.cs.binghamton.edu>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-freebsd-stable@FreeBSD.ORG
Precedence: bulk
X-Loop: FreeBSD.ORG


On Mon, 6 Sep 1999, Alex Povolotsky wrote:

> Hello!
> 
> The following program
> 
> #include <stdio.h>
> #include <fcntl.h>
> 
> main() {
> 	int control;
> 	if ((control = open("STATUS",O_WRONLY|O_NONBLOCK))<0) {
> 		perror("Could not open STATUS ");
> 		exit(1);
> 	}
> 	printf("STATUS ready\n");
> 	close(control);
> 	return(0);
> }
> 
> fails to run (STATUS is pre-created FIFO file) with error "Device not
> configured", which seems kinda odd for me.
> 
> However, when FIFO is opened with O_RDWR and O_NONBLOCK, every attempt 
> to select(2) its handler for writing doesn't wait until someone opens
> FIFO for reading, but instead FIFO is ready to write at every select.
> 
> Is it a bug or a feature?
> 

I answered a similar question some time ago.  You can search the mailing
list archive for this.  Basically, you need to read the "Advanced Unix
Programming Environment" by Stevens.  I can not remember every details
right now.  The "device not configured" error is expected. 

-Zhihui



To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message