linux-kernel - Re: 3.5.rc2 tty buffering bug ?

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Date:	Fri, 15 Jun 2012 18:32:54 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: 3.5.rc2 tty buffering bug ?

On Fri, Jun 15, 2012 at 12:13 AM, Dave Jones <davej@...hat.com> wrote:
> but when redirected to a file, sometimes it prints what we expect, but other times
> (if the child exits first) it seems to print..
>
> begin
> child
> end
> begin
> parent
> end
>
>
> How does 'begin' get printed a second time ?
>

setbuf(3) said:

"
Normally  all files are block buffered. [...]
If a stream refers to a terminal (as stdout normally does) it is line buffered.
The standard error stream stderr is always unbuffered by default.
"
So when you redirect stdout to a file, "begin\n" is buffered too, both
in child and in parent.
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