#!/bin/ksh
RETVAL=`sqlplus -s scott/pass@dev <<EOF
set serveroutput on
WHENEVER SQLERROR EXIT 1
declare
x number;
begin
x := 999;
dbms_output.put_line('the_result_is '||x);
end;
/
exit;
EOF`

echo $RETVAL
X=`echo $RETVAL | awk '{print $2}'`
echo $X

sqlplus -s scott/pass@dev <<EOF | read RETVAL
set serveroutput on
WHENEVER SQLERROR EXIT 1
declare
x number;
begin
x := 999;
dbms_output.put_line('the_result_is '||x);
end;
/
exit;
EOF

echo $RETVAL

X=`echo $RETVAL | awk '{print $2}'`
echo $X

Output as follows:
------------------
/home/scott >t.ksh
the_result_is 999 PL/SQL procedure successfully completed.
999
the_result_is 999
999