Type commandAppend('xxx') to append the output-files fort.7, fort.8, fort.9, to existing data-files s.xxx, b.xxx, and d.xxx (if you are using the default filename templates).
Type commandAppend('xxx','yyy') to append existing data-files s.xxx, b.xxx,
and d.xxx to data-files s.yyy, b.yyy, and d.yyy (if you are using
the default filename templates).