shell script and validating userid/password

Howdy Gurus,

We have a bourne shell script that we will be having a System Admin type in the username/password and connect string.

Example: run_shell_script jingle/claus_at_northpole_xya

In this shell script we are executing a sql*plus script.

Here's the scenario/proplem.

If the System Admin types in a wrong userid/password/dblink connect string, then when the sqlplus tries to use it, it just hangs and the shell script hangs.

What is the best way to validate the connect string? or
Is there a way to get sql*plus to auto exit out if the connect string is invalid?

We are NOT going to use the option of the "/" for many reasons. (Example: sqlplus /).

Thanks for any insight -----------------------------------------