-- beautifully the output 
SET LONG 20000 LONGCHUNKSIZE 20000 PAGESIZE 0 LINESIZE 1000 FEEDBACK OFF VERIFY OFF TRIMSPOOL ON

BEGIN
   DBMS_METADATA.set_transform_param (DBMS_METADATA.session_transform, 'SQLTERMINATOR', true);
   DBMS_METADATA.set_transform_param (DBMS_METADATA.session_transform, 'PRETTY', true);
END;
/

-- for a TRIGGER
SELECT DBMS_METADATA.get_ddl ('TRIGGER', trigger_name, owner)
FROM   all_triggers
WHERE  owner        = '&OWNER'
AND    trigger_name = '&TRIGGER_NAME';