From owner-freebsd-arch  Wed Sep 11  3:47:55 2002
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Date: Wed, 11 Sep 2002 20:55:32 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Archie Cobbs <archie@dellroad.org>
Cc: Bakul Shah <bakul@bitblocks.com>, <freebsd-arch@FreeBSD.ORG>
Subject: Re: /dev/stdout behavior
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On Tue, 10 Sep 2002, Archie Cobbs wrote:

> Bakul Shah writes:
> > You need to fix your test program similarly and run it under
> > Linux to see if the two OSes behave differently.
>
> They do behave differently, even after adjusting '0' to '1':
>
>     $ uname -a
>     Linux foobar.packetdesign.com 2.4.9 #19 SMP Mon Oct 29 11:55:31 PST 2001 i686 unknown
>     $ ./flags
>     O_NONBLOCK is not set

This is a bug in Linux IMO.  /dev/stdout should be as much like the real
stdout as possible.  E.g., it should share the file offset.  This requires
its descriptor to be a dup of stdout's descriptor for seekable files, and
it would be surprising if non-seekable files like ttys were different.
Sharing of O_NONBLOCK goes with sharing of the file (via diferent
descriptors).  Some device drivers have broken support for O_NONBLOCK
(they do extra work to make it per-device), but tty devies get this right.

Bruce


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