X-Recipient: archive-cygwin AT delorie DOT com
X-Spam-Check-By: sourceware.org
Date: Wed, 26 Nov 2008 15:50:52 +0100
From: Enrico Forestieri <forenr AT lyx DOT org>
To: cygwin AT cygwin DOT com
Subject: open() and named pipes
Message-ID: <20081126145052.GB16542@sirio.sssup.it>
Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="9jxsPFA5p3P2qPhR"
Content-Disposition: inline
User-Agent: Mutt/1.4.2.1i
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com

--9jxsPFA5p3P2qPhR
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

According to
http://www.opengroup.org/onlinepubs/000095399/functions/open.html
the open() function shall fail and sets errno to ENXIO if
O_WRONLY | O_NONBLOCK is set, the named file is a FIFO, and no
process has the file open for reading.

This is not the case on Cygwin, as demonstrated by the attached
test case. I get "This should not happen.", while the same program
outputs "No process is reading from the other end." on both Linux
and Solaris.

-- 
Enrico

--9jxsPFA5p3P2qPhR
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="openfifo.c"

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define FIFONAME "/tmp/xyz.xyz"

int main(void)
{
    int fd;
    if (mkfifo(FIFONAME, 0600) < 0) {
	perror("Error");
	exit(1);
    }
    fd = open(FIFONAME, O_WRONLY | O_NONBLOCK);
    if (fd >= 0) {
	puts("This should not happen.");
	close(fd);
    } else if (errno == ENXIO) {
	puts("No process is reading from the other end.");
    }
    remove(FIFONAME);
    return 0;
}


--9jxsPFA5p3P2qPhR
Content-Type: text/plain; charset=us-ascii

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/
--9jxsPFA5p3P2qPhR--