The suggested code
"sqlplus -s /nolog << EOF
connect user/pass
...
EOF"
will not do.

To make the case more clear :
1. I have a script
x1.sql as

select sysdate from dual
/
exit
2, I have a oracle user say u1 with passwd p1
3. I want to execute
sqlplus -s u1 @x1
4. I want it to prompt
Enter passwd :
5. It waits for passwd to be entered ..
If passord as "p1" is entered it returns the output as follows

$sqlplus -s p1 @x1
-- passwd q1 was entered without prompting which is not echoed

SYSDATE
-----------
15-OCT-2011
6. It is desired to get a prompt for entering passwd so that
some step can ne executed by operator for batch jobs.
7. I don't want to hard code the password in the script as
sqlplus -s u1/p1 @x1 which works any way. But everytime password is changed, script needs to be modified.