[oracle@rac1 ~]$ cd $ORACLE_HOME/sqlplus/admin
[oracle@rac1 admin]$ pwd
/u01/app/oracle/product/12.2.0.1/sqlplus/admin
[oracle@rac1 admin]$ ls -ltr
total 20
-rw-r--r--. 1 oracle dba  813 Mar  7  2006 plustrce.sql
-rw-r--r--. 1 oracle dba  226 Apr 29  2015 libsqlplus.def
-rw-r--r--. 1 oracle dba 2683 Jan  6  2016 pupbld.sql
drwxr-xr-x. 2 oracle dba 4096 Jan 13  2017 help
-rw-r--r--. 1 oracle dba  422 Aug 29 09:27 glogin.sql
[oracle@rac1 admin]$
[oracle@rac1 admin]$ cat glogin.sql
--
-- Copyright (c) 1988, 2005, Oracle.  All Rights Reserved.
--
-- NAME
--   glogin.sql
--
-- DESCRIPTION
--   SQL*Plus global login "site profile" file
--
--   Add any SQL*Plus commands here that are to be executed when a
--   user starts SQL*Plus, or uses the SQL*Plus CONNECT command.
--
-- USAGE
--   This script is automatically run
--
[oracle@rac1 admin]$ 

-- Connect as oracle user and add the following line at the end of the glogin.sql script.
-- Added by Rajasekhar Amudala
set sqlprompt "_user '@' _connect_identifier > "

[oracle@rac1 admin]$ cat glogin.sql
--
-- Copyright (c) 1988, 2005, Oracle.  All Rights Reserved.
--
-- NAME
--   glogin.sql
--
-- DESCRIPTION
--   SQL*Plus global login "site profile" file
--
--   Add any SQL*Plus commands here that are to be executed when a
--   user starts SQL*Plus, or uses the SQL*Plus CONNECT command.
--
-- USAGE
--   This script is automatically run
--
-- Added by Rajasekhar Amudala
set sqlprompt "_user '@' _connect_identifier > "

[oracle@rac1 admin]$ sqlplus / as sysdba

SQL*Plus: Release 12.2.0.1.0 Production on Wed Aug 29 09:28:14 2018

Copyright (c) 1982, 2016, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SYS @ CDB2 > select name,open_mode from v$database;

NAME      OPEN_MODE
--------- --------------------
CDB2      READ WRITE

SYS @ CDB2 > show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 PDB1                           READ WRITE NO
         4 PDB2                           READ WRITE NO
         5 PDB3                           READ WRITE NO
         6 PDB4                           READ WRITE NO
SYS @ CDB2 >
SYS @ CDB2 > connect sys@PDB1 AS SYSDBA
Enter password:
Connected.
SYS @ PDB1 >
SYS @ PDB1 > show con_name

CON_NAME
------------------------------
PDB1
SYS @ PDB1 >