how watch and record video from multiple webcam cameras on raspberry pi at the same time [duplicate]

I want to watch and record video from multiple webcam cameras on raspberry pi at the same time. How I use OpenCV library file?Which software I use?And I waa put webcam cameras away 20 feet from sever raspberry pi board.It ok?And I waa transmit video to network.. I am now studying Raspberry pi,so guide me please.