Help, question about "select ... for update nowait"

Question

There is a proc code. In the beginning of the code, I used a SQL "select ... for update nowait" in order to prevent from another proc executing at the same time. When the case happens, "-54, ORA-00054: resource busy and acquire with NOWAIT specified" will be printed in the screen.
But there is a question: I need to print sth to indicate "another proc is running". I used "if (sqlca.sqlcode == -54)" as precondition, such as:
if (sqlca.sqlcode == -54) {
printf("There is another proc running.\n");
However, this line will not be printed. I doubt that the code quits directly when using "select ... for update nowait" so as not to set value (-54) to sqlca.sqlcode.
So, could you suggest whether there is another way that I can use to print "There is another proc running" when another proc is running?
Thx a lot for your kindly reply.

Answer 1

Yes, that link. Scroll down a bit and you will see:
The calling application gets a PL/SQL exception, which it can process using the error-reporting functions SQLCODE and SQLERRM in an OTHERS handler. Also, it can use the pragma EXCEPTION_INIT to map specific error numbers returned by raise_application_error to exceptions of its own, as the following Pro*C example shows:
EXEC SQL EXECUTE
/* Execute embedded PL/SQL block using host
variables v_emp_id and v_amount, which were
assigned values in the host environment. */
DECLARE
null_salary EXCEPTION;
/* Map error number returned by raise_application_error
to user-defined exception. */
PRAGMA EXCEPTION_INIT(null_salary, -20101);
BEGIN
raise_salary(:v_emp_id, :v_amount);
EXCEPTION
WHEN null_salary THEN
INSERT INTO emp_audit VALUES (:v_emp_id, ...);
END;
END-EXEC;
This technique allows the calling application to handle error conditions in specific exception handlers.