linux-kernel - Re: [PATCH] setlocalversion: Use "grep -q" instead of piping output to "read dummy"

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Date:	Mon, 26 Mar 2012 22:58:04 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	Roland Dreier <roland@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] setlocalversion: Use "grep -q" instead of piping output
 to "read dummy"

On Fri, Mar 23, 2012 at 09:42:27AM -0700, Roland Dreier wrote:
> From: Roland Dreier <roland@...estorage.com>
> 
> In some circumstances (eg when running a build in an emacs shell
> buffer), I get a spew of messages like
> 
>     grep: writing output: Broken pipe
> 
> from setlocalversion, because the "read" subshell apparently exits as
> soon as it reads one line and gives EPIPE to grep.  It's not clear to
> me why this way of writing the check was used instead of just using
> grep -q to suppress output, but unless there is some deep reason I
> don't know, this way looks cleaner to me anyway, and gets rid of the
> ugly message spew.

I guess the author was used to write it this way, because ancient grep
versions did not have -q.


> (I double checked at http://pubs.opengroup.org/onlinepubs/009604499/utilities/grep.html
> and "grep -q" is specified in POSIX / SuS, so hopefully even people
> cross-compiling the kernel on some bizarre host OS can't complain
> about this change)

Yeah, I think it's safe. Thanks for double-checking.

Applied to kbuild.git#kbuild now.

Michal
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