Connect to Oracle database using command line on Ubuntu 16.04

1. Download Oracle client package (instantclient-basiclite-linux.x64-19.8.0.0.0dbru.zip) and sqlplus commandline client package (instantclient-sqlplus-linux.x64-19.8.0.0.0dbru.zip) from here
Your may have latest versions, download them.

2. Now run commands

mkdir -p /opt/oracle
cd /opt/oracle

3. Unzip downloaded package instantclient-basiclite-linux.x64-19.8.0.0.0dbru.zip

unzip instantclient-basiclite-linux.x64-19.8.0.0.0dbru.zip

and move folder instantclient_19_8 in /opt/oracle

4. Install libaio package

sudo apt install libaio-dev

5. Run Commands

sudo sh -c "echo /opt/oracle/instantclient_19_8 > /etc/ld.so.conf.d/oracle-instantclient.conf"
  
sudo ldconfig

or

export LD_LIBRARY_PATH=/opt/oracle/instantclient_19_8:$LD_LIBRARY_PATH

6. Unzip downloaded package instantclient-sqlplus-linux.x64-19.8.0.0.0dbru.zip

unzip instantclient-sqlplus-linux.x64-19.8.0.0.0dbru.zip

Copy all .so files of these extracted zip into /opt/oracle/instantclient_19_8

mv *.so /opt/oracle/instantclient_19_8

7. Now connect to oracle db on command line.

./sqlplus username/password@domain:port/service_name

Example :

./sqlplus root/strongpassword@54.24.xxx.xxx:1532/ORCAD

8. After connect to sql prompt, list all databases using query

select * from v$database;

Query to view the schema name by

select * from dba_users;

To display the columns available in the Oracle view v$database, we can execute the below statement.

desc v$database;