From owner-freebsd-hackers  Wed Jan 16  2:48:54 2002
Delivered-To: freebsd-hackers@freebsd.org
Received: from gw.gbch.net (gw.gbch.net [203.143.238.93])
	by hub.freebsd.org (Postfix) with SMTP id 4A53437B41A
	for <freebsd-hackers@freebsd.org>; Wed, 16 Jan 2002 02:48:48 -0800 (PST)
Received: (qmail 76661 invoked by uid 1001); 16 Jan 2002 20:48:46 +1000
X-Posted-By: GJB-Post 2.23 27-Nov-2001
X-Operating-System: FreeBSD 4.2-RELEASE i386
X-Uptime: 7 days,  3:15
X-Location: Brisbane, Australia; 27.49841S 152.98439E
X-URL: http://www.gbch.net/gjb.html
X-Image-URL: http://www.gbch.net/gjb/gjb-auug048.gif
X-GPG-Fingerprint: EBB2 2A92 A79D 1533 AC00  3C46 5D83 B6FB 4B04 B7D6
X-PGP-Public-Keys: http://www.gbch.net/keys.html
Message-Id: <nospam-1011178126.76622@bambi.gbch.net>
Date: Wed, 16 Jan 2002 20:48:46 +1000
From: Greg Black <gjb@gbch.net>
Mail-Followup-To: Foldi Tamas <crow@localhost.hu>
To: Foldi Tamas <crow@localhost.hu>
Cc: freebsd-hackers@freebsd.org
Subject: Re: interesting open() issue 
References: <20020116105923.A29210@hax0r.hu> 
In-reply-to: <20020116105923.A29210@hax0r.hu> 
	of Wed, 16 Jan 2002 10:59:23 +0100
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-hackers.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-hackers>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-hackers>
X-Loop: FreeBSD.ORG

Foldi Tamas wrote:

| Hello hackers,

Don't send this sort of newbie programmer question to the
hackers list (or to any of the FreeBSD lists).

| 	I tried the following program on Tru64, FreeBSD and linux:
| 
| #include <stdio.h>
| #include <fcntl.h>
| #include <sys/stat.h>
| #include <sys/types.h>
| main() {
|         int fd;
|         fd = open ( "/tmp/foobar", (O_RDWR | O_CREAT),  0020);
|         perror("open");
|         close(fd);
| }
| 
| The program ran successfully, but the created file was different.
| On Linux:
|     -----w----    1 crow     crow            0 Jan 16 10:32 /tmp/foobar
| 
| On Tru64/FreeBSD:
|     ----------    1 crow     users           0 Jan 16 10:30 /tmp/foobar
| 
| I'm not sure what the result supposed to be. Any ideas ?

If you want the exact same results on each system and if you
want the file to have the mode you set, you need to put two
additional system calls *before* the open(2) call:

    unlink("/tmp/foobar");
    umask(0);

If the file exists, the mode in the open() won't affect it and
it will retain whatever it already had, so you need to ensure
that it's not there first.  If your umask setting masks the
group write bit, it won't be set unless you first clear the
umask setting.

Now go and read about Unix programming.

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