def agefilter(st, now, age, timestamp):
    """filter files older than age"""
    if age is None:
        return True
    elif age >= 0 and now - st.__getattribute__('st_%s' % timestamp) >= abs(age
        ):
        return True
    elif age < 0 and now - st.__getattribute__('st_%s' % timestamp) <= abs(age
        ):
        return True
    return False
