In first example, i can show these:
[oracle@localhost~] echo “select count(*) from tab;” | sqlplus -s username/pass
With another method, you can run from one Linux command a SQL file
 [oracle@localhost~] sqlplus -s username/pass <filename.sql
 COUNT(*)
————-
                20
  1. alias sysdba=‘select status, instance_name from v$instance; | sqlplus / as sysdba’
  2. alias sysoper=‘sqlplus / as sysoper’
  3. alias rman=‘rman target / ‘