[Xen-devel] Re: [PATCH 3 of 3] [xen-detect] Add arguments to print out only outputs we are interested in

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Dec 22, 2009 at 08:21:14PM +0000, Keir Fraser wrote:
> On 22/12/2009 16:48, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:
> 
> > # HG changeset patch
> > # User konrad@xxxxxxxxxxxxxxxxxxx
> > # Date 1261498156 18000
> > # Node ID 04c067941b17bdc679ffdc2f6c81f8e2f78e9cc5
> > # Parent  7bd805a543da685a3dba7b8b0c4e3e7052c863b3
> > [xen-detect] Add arguments to print out only outputs we are interested in.
> > 
> > This is quite usefull in scripts where you can do
> > if xen-detect -P || modprobe xen-<some module>
> > 
> > And do not have to parse the output - instead you will get
> > the output only if the condition exists.
> 
> Er, what? The above shell fragment is affected by the value returned by
> xen-detect (0 versus non-0), not by whether it prints something!

Wrong combination. Here is what the Dracut maintainer suggested:

[konrad@phenom ~]$ if xen-detect; then echo blah; fi
Not running on Xen.
blah

Which is not what I wanted it to do. Having the -N, -P, -H arguments
fixed the issue.

> 
> Here is my suggestion: keep your new command-line options, but instead of
> affecting printing, have them affect the return value. E.g., -P causes
> return 0 if running PV, else return 1. Further, we can add a -q option to
> quiesce normal output from xen-detect, to make it quieter for use in shell
> scripts.
> 
> E.g, xen-detect -Pq && modprobe some-xen-pv-specific-module
> 
> What do you think of that?

That should do it. Will post a rework after the X-mas holidays.

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