Running sqlplus from a unix shell script, how do I handle passwords?

[Suwarna]

I agree that OS Authentication is the best means of doing it.
However if I want to follow the properties file approach, how do I pass the username/password to the sqlplus command via shell script? I am doing something like -

DBURL=$(cat temp.txt)
echo $DBURL

sqlplus $DBURL << EOF
exec packageName.procName();
EOF

The sqlplus command is not recognizing the DBURL parameter. How do I pass this shell script variable to sqlplus command?
I am new to shell scripting. Please help.
Thanks.........