[CentOS] Old and new package version numbers during RPM update

Mon Jun 29 09:43:25 UTC 2015
Leon Fauster <leonfauster at googlemail.com>

Am 29.06.2015 um 02:11 schrieb Anand Buddhdev <anandb at ripe.net>:
> On 29/06/15 01:07, Kahlil Hodgson wrote:
>> On 29 June 2015 at 07:37, John R Pierce <pierce at hogranch.com> wrote:
>>> so a regex looking for "system:" vs "system {"   should nicely delineate
>>> these.   I dunno, I might even put that into the conversion utility and
>>> have it just quit if the file is already in the new format, and always run
>>> it.
>> ​+1 for the idempotent approach. IMHO much more robust. Also consider what
>> will happen if someone does a 'yum downgrade' on the package or a
>> dependency -- you might want to allow the conversion to go both ways or at
>> least complain appropriately.
> Yep. I've already considered this approach, but I avoid regexes as much
> as possible. They're great for some work, but they can inadvertently
> match too much or fail (for example if the "system" keyword and the
> opening brace are on different lines). You see where I'm going? But,
> this is a digression...

that is exactly what regex can do for you. it confirms the "language" 
of the config file, unattached from new lines or space characters. 
Sure, the expression itself is more "complicated" ... (a combination
of tools is also possible eg. tr, awk, sed, grep)