Export DDL with DBMS_METADATA

SQL>
exec dbms_metadata.set_transform_param(dbms_metadata.session_transform, 'SQLTERMINATOR', true);
exec dbms_metadata.set_transform_param(dbms_metadata.session_transform, 'STORAGE', false);
exec dbms_metadata.set_transform_param(dbms_metadata.session_transform, 'TABLESPACE', false);
exec dbms_metadata.set_transform_param(dbms_metadata.session_transform, 'SEGMENT_ATTRIBUTES', false);

select
  dbms_metadata.get_ddl('FUNCTION','SAMPLE_FUNC','APPUSER')
from dual;