You can shutdown/startup the Oracle database by using UNIX command without login to sqlplus.

If you are under RAC environment, the command below will start/shutdown all the database in the RAC environment.

To stop the Oracle database using srvctl command

UNIX> srvctl stop database -d

To stop the Oracle database using srvctl command

 UNIX> srvctl start database -d

To check status of the Oracle database using srvctl command

UNIX> srvctl status database -d

If you are not sure what is your database name or is, use the command below to check

SQL> SELECT name FROM v$database;