Possible to check version of package in %pre/%prerun -> -> changes outcome of install ?

[Panu Matilainen]

On 10/07/2014 11:00 AM, Morgan Cox wrote:
> Hi
>
> I am trying to build an RPM that when installed/upgraded checks the
> present version of the package and depending on if the present version
> is a certain version or higher -> do something if lower -> do something
> else.
>
> i.e if present version is 1.0 or higher -> do something
>
> else
>
> if present present version is < 1.0 -> do something else.
>
> I have been told that I shouldn't use rpm command (i.e 'rpm-qa')  in the
> inside the %pre or %prerun  scriptlet as this can cause an RPM - how can
> I query the existing version in the rpmbuild/spec file?

Doing rpm queries from inside rpmbuild isn't any more recommended than 
install-time scriptlets, for similar reasons, and it wouldn't help 
anyway if you need to do such decisions at install-time.

What you can do from rpm scriptlets is try figuring out the version by 
other means, such as testing existence/naming of files of the other 
package, or executing some test-commands (lot of software has some means 
of outputting its version via --version or such cli switch)

	- Panu -