define HOT_BACK_DIR = '&backup_directory'
define SCRIPT_FILE =  '&script_file'

column F_HOT_BACK_DIR new_value HOT_BACK_DIR
select  nvl('&HOT_BACK_DIR','/tmp') F_HOT_BACK_DIR from dual;
select '&HOT_BACK_DIR' "BACKUP DIRECTORY" from dual;

column F_SCRIPT_FILE new_value SCRIPT_FILE
select  nvl('&SCRIPT_FILE','backup.sql') F_SCRIPT_FILE from dual;
select '&SCRIPT_FILE' "SCRIPT FILE" from dual;

set feedback off
set heading off
set pagesize 0
set linesize 128
set verify off
set termout oN
set echo off
set trims on

spool &SCRIPT_FILE

select 'set echo on' from dual;
select 'connect / as sysdba' from dual;

-- make a ascii script backup of controlfile
select 'alter database backup controlfile to trace; ' from dual;

-- the ascii backup is written udump
-- the following tries to receate the full path and name
-- of the trace file containing the controlfile backup
-- so we can copy it to the backup directory
prompt column tracefile new_value trace_file
prompt select
prompt      (select value from v$parameter where name='user_dump_dest')||'/'||
prompt      (select lower(value) from v$parameter where name='db_name')||
prompt      '_ora_' || p.spid ||'.trc' tracefile
prompt from
prompt       v$process p,
prompt       v$session s
prompt where s.paddr = p.addr
prompt   and s.sid = ( select distinct sid from v$mystat)
prompt /
prompt

-- outputs "!cp &trace_file /backup'
-- which when run in the output script, copies
-- the tracefile with the controlfile script to the backupdir
select '!cp ' ||Chr(38)|| 'trace_file' || '  &HOT_BACK_DIR/control.trc'  from dual;
select '!cat ' ||Chr(38)|| 'trace_file' || ' | awk "/current/,/OFF/{ print}" | grep -v
"^#"   > &HOT_BACK_DIR/control.sql'  from dual;

spool off