linux-kernel - Re: [PATCH] ver_linux: module-init-tools.patch

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Message-ID: <CAJ1xhMW6rfMTc8aqnqfqLOyzApCbnvkVK0ETyd2UO1WZf+kcYQ@mail.gmail.com>
Date:	Fri, 2 Oct 2015 22:03:20 +0300
From:	Alexander Kapshuk <alexander.kapshuk@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Jim Davis <jim.epost@...il.com>
Subject: Re: [PATCH] ver_linux: module-init-tools.patch

On Fri, Oct 2, 2015 at 9:10 PM, Jim Davis <jim.epost@...il.com> wrote:
> On Thu, Oct 1, 2015 at 11:49 AM, Alexander Kapshuk
> <alexander.kapshuk@...il.com> wrote:
>> The current implementation relies on 'depmod' to be available in the
>> PATH. It also expects the version number to be found in the last field
>> as seen by 'awk'. Should the output format be different, this approach
>> would no longer be reliable.
>>
>> The proposed implementation locates 'depmod', and uses 'sed' as a more
>> flexible tool to handle varying output formats.
>>
>> Tested on:
>> Gentoo Linux
>> Debian 6.0.10
>> Oracle Linux Server release 7.1
>> Arch Linux
>> openSuSE 13.2
>>
>>
>> Signed-off-by: Alexander Kapshuk <alexander.kapshuk@...il.com>
>> ---
>>
>> --- linux/scripts/ver_linux.orig    2015-10-01 18:36:49.090519891 +0300
>> +++ linux/scripts/ver_linux    2015-10-01 21:48:09.985628346 +0300
>> @@ -25,7 +25,14 @@
>>  echo -n "mount                  "
>>  mount --version | awk '{print $NF}' | sed -e s/^mount-// -e s/\)$//
>>
>> -depmod -V  2>&1 | awk 'NR==1 {print "module-init-tools     ",$NF}'
>> +depmod=`whereis depmod | awk '{print $2}'`
>
> Hmm.
>
> jim@...bstar:~$ which depmod
> /usr/local/bin/depmod
> jim@...bstar:~$ whereis depmod
> depmod: /sbin/depmod /etc/depmod.d /usr/local/bin/depmod
> /usr/share/man/man8/depmod.8.gz
>
> So while according to my $PATH preferences I'd rather run
> /usr/local/bin/depmod, it looks like the '{print $2}' thing would pick
> /sbin/depmod instead.
>
> Not a big deal, but I suspect those sort of considerations are why the
> scripts tend just to check the $PATH.
>
> --
> Jim

Thanks for your feedback.

Is '/sbin/depmod' perhaps a symlink to '/usr/local/bin/depmod' on your system?

On some distros, I found that 'which' may not necessarily locate the
binary in question, because the $PATH is not set in a uniform fashion
across various distros. Whereas 'whereis' was found to return a valid
path to the binaries invoked by 'ver_linux' across all the distros I
have been able to test-run 'ver_linux' on, especially on those where
'which' failed to do so. Which is something I found confusing
considering the fact the manpages for both 'which' and 'whereis' claim
to be searching the $PATH to find binaries.

E.g. on Gentoo I get this:

which depmod
which: no depmod in
(/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.8.5:/usr/games/bin:/home/alkap/bin:/usr/local/plan9/bin)

whereis -b depmod
depmod: /sbin/depmod

ls -l /sbin/depmod
lrwxrwxrwx 1 root root 9 Aug  8 14:47 /sbin/depmod -> /bin/kmod

If you have a more reliable approach to suggest, I am open to suggestions.

Thanks.
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