In the Linux world and some other Unix dialects the directory /etc/profile.d can be used to execute shell scripts for ALL UNIX / Linux users.
A vendor at one of my clients used this feature to setup Oracle environment variables in a file named /etc/profile.d/oracle.sh like ORACLE_HOME – as a result – if I upgrade Oracle – we need to change this script to point to the new home etc. to match our upgrade.
E.g.
export ORACLE_HOME=/u01/app/oracle/product/12.1.0/dbhome_1
export ORACLE_HOME=/u01/app/oracle/product/12.2.0/dbhome_1