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Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm
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From: "Michel LaBarre" <michel.labarre@rogers.com>
To: "'Alexander Pelevin'" <pvshura@mail.ru>, <cygwin@cygwin.com>
References: <002901d3b0fd$a30dee50$e929caf0$@mail.ru>
In-Reply-To: <002901d3b0fd$a30dee50$e929caf0$@mail.ru>
Subject: RE: Possible output redirect bug
Date: Wed, 28 Feb 2018 22:02:12 -0500
Message-ID: <000601d3b109$b33e8f80$19bbae80$@rogers.com>
MIME-Version: 1.0
Content-Type: text/plain;	charset="iso-8859-1"
Content-Transfer-Encoding: 8bit

> Subject: Possible output redirect bug
> 
> Error output is not suppressed:
> 
> 
> $ cygstart cmd /c "(  >&2 pause ) >> test.txt"
> 
> $ cat /dev/null >> test.txt >/dev/null 2>&1
> bash: test.txt: Device or resource busy

The error message is not from the process running "cat" which is to what the
redirections apply.
The message is coming from the shell trying to setup file descriptors to
pass to the process running "cat" - you can see "bash:"
The shell cannot open the file for appending.

A simpler demonstration is:
$ cat < zorch > /dev/null 2>&1
bash: zorch: No such file or directory

Alternately:
$ ls zorch
ls: cannot access 'zorch': No such file or directory

shows std err is from "ls" and:
$ ls zorch 2> /dev/null
$
demonstrates redirection working.

Try instead:
( cat /dev/null >> test.txt ) >/dev/null 2>&1

Cheers,
Michel


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