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Re: [Xen-devel] [PATCH] xend: update init script to avoid grep on non-ex

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xend: update init script to avoid grep on non-existent file system
From: Richie <listmail@xxxxxxxxxxxx>
Date: Sat, 15 May 2010 10:56:00 -0400
Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Sure. I agree much simpler, but is this blurb in the grep manpage a concern?
-s, --no-messages
Suppress error messages about nonexistent or unreadable files.
Portability note: unlike GNU grep, 7th Edition Unix grep did not
conform to POSIX, because it lacked -q and its -s option behaved
like GNU grep’s -q option. USG-style grep also lacked -q but
its -s option behaved like GNU grep. *Portable shell scripts
should avoid both -q and -s and should redirect standard and
error output to /dev/null instead*. (-s is specified by POSIX.)

I'm not sure where all the xend daemon can run? is it always running on linux, thus implying (modern?) GNU grep? The reason I am bringing this up is that I recall having grep related issues when running git on Solaris (without gnu utilities installed) for this very reason. I will re-sumbit accordingly.

Keir Fraser wrote:
On 15/05/2010 05:16, "Richie" <listmail@xxxxxxxxxxxx> wrote:

I'm seeing a grep error during bare metal pvops kernel boot.  In the
init script, the previous checks will avoid/perform the /proc/xen mount
as appropriate, but then it does a grep on /proc/xen/capabilities
without ensuring that /proc/xen is actually mounted.  This is my attempt
(read: first patch :) ) to avoid it.


Can you try adding the -s option to grep instead (i.e., grep -qs)? Should be
a simpler way to achieve the same thing. I'll apply that instead if it works
okay for you.

 -- Keir

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