how to switch off or reboot phone using root ?

root@j2lte:/ # svc power
Control the power manager

usage: svc power stayon [true|false|usb|ac|wireless]
         Set the 'keep awake while plugged in' setting.
       svc power reboot [reason]
         Perform a runtime shutdown and reboot device with specified reason.
       svc power shutdown
         Perform a runtime shutdown and power off the device.

root@j2lte:/ # svc power reboot becauseican