From owner-freebsd-arch  Tue Sep 10 10: 0: 6 2002
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From: Archie Cobbs <archie@dellroad.org>
Message-Id: <200209101656.g8AGuJ433605@arch20m.dellroad.org>
Subject: /dev/stdout behavior
To: freebsd-arch@freebsd.org
Date: Tue, 10 Sep 2002 09:56:19 -0700 (PDT)
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Is there an 'official' spec about how /dev/stdout is supposed to behave?

For example, if you use fcntl() to set flags on fd 0, and then open
/dev/stdout, the new file descriptor you get back will have those
same flags set. Run the program below to see an example. This is
in agreement with the man page, which states that opening /dev/stdout
is equivalent to dup(2)'ing fd 0.

However, on RedHat Linux 7.3, the program below behaves in the opposite
manner from FreeBSD, i.e., it prints "O_NONBLOCK is not set".

So at least one of FreeBSD or Linux is 'wrong' about /dev/stdout, or maybe
there is no general agreement about what /dev/stdout means..  ?

Thanks,
-Archie

P.S. This issue underlies PR misc/41331:
	http://www.freebsd.org/cgi/query-pr.cgi?pr=41331

__________________________________________________________________________
Archie Cobbs     *     Packet Design     *     http://www.packetdesign.com

#include <stdio.h>
#include <fcntl.h>
#include <err.h>

int
main(int argc, char **argv)
{
	int flags;
	int fd;

	if ((flags = fcntl(0, F_GETFL, 0)) == -1)
		err(1, "fcntl");
	if (fcntl(0, F_SETFL, flags | O_NONBLOCK) == -1)
		err(1, "fcntl");
	if ((fd = open("/dev/stdout", O_WRONLY, 0)) == -1)
		err(1, "open");
	if ((flags = fcntl(fd, F_GETFL, 0)) == -1)
		err(1, "fcntl");
	printf("O_NONBLOCK is %s\n", (flags & O_NONBLOCK) ? "set" : "not set");
	return (0);
}


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