[LTP] [PATCH ltp] ver_linux: check /usr/lib/os-release in case /etc/os-release not exists

[Petr Vorel]

Hi Yixin,

> https://www.linux.org/docs/man5/os-release.html:
>   "The file /etc/os-release takes precedence over /usr/lib/os-release.
>   Applications should check for the former, and exclusively use its data
>   if it exists, and only fall back to /usr/lib/os-release if it is missing.
>   Applications should not read data from both files at the same time.
>   /usr/lib/os-release is the recommended place to store OS release
>   information as part of vendor trees.  /etc/os-release should be a
>   relative symlink to /usr/lib/os-release, to provide compatibility with
>   applications only looking at /etc. A relative symlink instead of an
>   absolute symlink is necessary to avoid breaking the link in a chroot or
>   initrd environment such as dracut."

> To be compatible with some distro which don't have the soft link
> "/etc/os-release", check "/usr/lib/os-release" first before checking
> "/etc/issue".

> Signed-off-by: Yixin Zhang <yixin.zhang@intel.com>
> ---
>  ver_linux | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

> diff --git a/ver_linux b/ver_linux
> index dda337926..f4c4e07f4 100755
> --- a/ver_linux
> +++ b/ver_linux
> @@ -9,8 +9,12 @@ echo 'If some fields are empty or look unusual you may have an old version.'
>  echo 'Compare to the current minimal requirements in Documentation/Changes.'

>  echo
> -echo "`ls /etc/*release`"
> +echo "`ls /etc/*release 2> /dev/null`"
>  cat /etc/*release 2> /dev/null
> +if [ $? = 1 ]; then
> +   echo "`ls /usr/lib/*release 2> /dev/null`"
> +   cat /usr/lib/*release 2> /dev/null
> +fi
>  if [ $? = 1 ]; then
>     echo '/etc/issue:'
>     cat /etc/issue 2> /dev/null

How about, instead of repeating files with cat, find the file and then work with it?
Something like this:

f="$(ls /etc/*release 2>/dev/null)"
[ -f "$f" ] || f="$(ls /usr/lib/*release 2>/dev/null)"
[ -f "$f" ] || f="$(ls /etc/issue 2>/dev/null)"
if [ -f "$f" ]; then
	echo "$f:"
	cat $f
fi

We could also run `lsb_release -a' (if available).


Kind regards,
Petr