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From:	"Alexander Pelevin via cygwin" <cygwin AT cygwin DOT com>
Reply-To:	"Alexander Pelevin" <pvshura AT mail DOT ru>
To:	"'Michel LaBarre'" <michel DOT labarre AT rogers DOT com>, <cygwin AT cygwin DOT com>
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In-Reply-To:	<000601d3b109$b33e8f80$19bbae80$@rogers.com>
Subject:	RE: Possible output redirect bug
Date:	Wed, 28 Feb 2018 19:10:27 -0800
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You are right, thank you for the explanation.

Alex.

-----Original Message-----
From: cygwin-owner AT cygwin DOT com [mailto:cygwin-owner AT cygwin DOT com] On Behalf Of
Michel LaBarre
Sent: Wednesday, February 28, 2018 7:02 PM
To: 'Alexander Pelevin'; cygwin AT cygwin DOT com
Subject: RE: Possible output redirect bug

> 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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