How to check if a RU is installed or covered?

Hi,

Before installing a new RU, we need to check if a RU has been installed or has been covered by the current RU in the system. We need to do that by script, so the method to judge that should be as simple as possible. 

On Oracle 12.1.0.2, if I want to install a PSU, I can check the system by "opatch lsinv" which will list the current PSU installed and also it will list all the preceding PSUs even if I did not install them explicitly.  For example, if I only installed 12.1.0.2.190115, it will also list the previous 12.1.0.2.181016, 12.1.0.2.180717, etc. as below: