Just be careful with that, because if a user on unix does a

/usr/proc/bin/ptree

they potentially could see your username and password running the script.

A better method I think would be

USER1="scott"
PASS1="tiger"
COM2="connect $USER1/$PASS1"
COM3="sqlplus /nologon"

$COM3 < $COM2
set serveroutput on
execute test_package.test_procedure
ESQL

Cheers,