树莓派连接WiFi 配置

pi@raspberrypi:/etc/network$ /etc/init.d/networking  restart
Running /etc/init.d/networking restart is deprecated because it may not re-enable some inter                                                                            faces ... (warning).
Reconfiguring network interfaces.../etc/network/interfaces:21: option with empty value
ifdown: couldn't read interfaces file "/etc/network/interfaces"
/etc/network/interfaces:21: option with empty value
ifup: couldn't read interfaces file "/etc/network/interfaces"
failed.