<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def get_routes(iface):
    '''
    Return the routes for the interface

    CLI Example:

    .. code-block:: bash

        salt '*' ip.get_routes eth0
    '''

    filename = os.path.join(_DEB_NETWORK_UP_DIR, 'route-{0}'.format(iface))
    results = _read_file(filename)

    filename = os.path.join(_DEB_NETWORK_DOWN_DIR, 'route-{0}'.format(iface))
    results += _read_file(filename)

    return results