How to identify ORACLE_HOME of an Oracle instance process?

How to identify ORACLE_HOME of an Oracle instance process?
Use strings /proc//environ | grep ORACLE_HOME

For, instance,
ps -ef|grep pmon
oracle 9466     1  0  2016 ?        00:29:36 ora_pmon_DBName

$ strings /proc/9466/environ | grep ORACLE_HOME
ORACLE_HOME=/oracle/app/product ...