sqlplus from Unix...checking for errors etc.

I want to run sqlplus from a Korn Shell script.

I see 3 problems. :

1. Can I check Oracle is available before running sqlplus?
2. How should I check for sqlplus errors?
3. How can I return variables from sqlplus to the shell script?

The sql is simple(see below). I want to return var_status and var_error_message to the Korn Shell script

var_status VARCHAR2(25);
var_error_message VARCHAR2(100);

BEGIN var_status := get_customer_status('CUSTOMER', 0, 'PHASE1', var_error_message); Received on Mon Oct 09 2000 - 06:33:36 CDT