How does one list all installed Oracle products?

Body: 

One can display all installed products with version information by executing one of the following commands:

For Oracle 8i and above:

cd $ORACLE_HOME/install
cat unix.rgs

For Oracle7 up to 8.0:

cd $ORACLE_HOME/orainst
./inspdver

Comments

eux981{orahubti}# view unix.rgs
"unix.rgs" [Read only] 1 line, 16 characters
rdbms 9.2.0.0.0

So, unix.rgs only contains the single product. Any other command?