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Date: Mon, 17 Oct 2016 11:00:36 -0700
From: Linda Walsh <cygwin AT tlinx DOT org>
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Subject: Re: /dev/stderr problem
References: <nu1qtk$te3$1 AT blaine DOT gmane DOT org> <nu1rav$te3$2 AT blaine DOT gmane DOT org> <1957a989-fe56-ca68-ddc2-83bc59480ccd AT redhat DOT com>
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Eric Blake wrote:
> On 10/17/2016 01:32 AM, Thorsten Kampe wrote:
>> * Thorsten Kampe (Mon, 17 Oct 2016 08:25:13 +0200)
>>
>>> the following bash script results in a different output when 
>>> redirected to a file.
>>>
>>> ```
>>> printf "FIRST LINE\n" > /dev/stderr
>>> shopt -os xtrace
>>> printf "SECOMD LINE\n" > /dev/stderr
> 
> Cygwin treats '> /dev/stderr' as a request to truncate /dev/stderr (or,
> for that matter, any opening of a file under /proc/self/fd).  Other
> platforms treat that as a special file that can never be truncated, but
> is instead reopened at the same offset.
> 
> Maybe cygwin can be taught that opening a file through /proc/self/fd
> should preserve rather than reset offsets, but it will be a tricky
> patch, and someone has to write it.
---
Is /dev/stderr a POSIX special name that one should expect that rewinding
is disallowed or ignored?

Good analysis, BTW, that sure would have puzzled me.
-l


> 

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