How to find if a psu is applied or not on an Oracle database

Please make sure that ORACLE_HOME/OPatch is in your PATH, afterwards execute

opatch lsinventory -bugs_fixed | grep -i 'database psu'

Expected Output:

10248523   12419331  Fri Sep 16 21:09:53 PKST 2011  DATABASE PSU 11.2.0.2.1

11724916   12419331  Fri Sep 16 21:09:53 PKST 2011  DATABASE PSU 11.2.0.2.2 (INCLUDES CPUAPR2011)

12419331   12419331  Fri Sep 16 21:09:53 PKST 2011  DATABASE PSU 11.2.0.2.3 (INCLUDES CPUJUL2011)