Unix to Oracle help needed

I have a Unix script which calls sql*plus to run a sql script, I want the sql script to return the single value (a character eg "A") from a select statement.

the UNIX script does this:

sqlplus -s login/password @$sqlfile/sqlScrip.sql
ret_val=$?

and

the SQL script does this:

set heading off
whenever SQLERROR EXIT 99

REM Only a single value in this Table.
select STATUS
from TBLINTERFACE_MESSAGE;

exit


but all I manage to capture is the exit code from sql*plus (ie 0 not "A"), not the value returned from the SQL select

can anyone help?