You can list all connected cameras using
v4l2-ctl --list-devices
Example output:
bcm2835-codec-decode (platform:bcm2835-codec): /dev/video10 /dev/video11 /dev/video12 /dev/video18 /dev/video31 /dev/media0 bcm2835-isp (platform:bcm2835-isp): /dev/video13 /dev/video14 /dev/video15 /dev/video16 /dev/video20 /dev/video21 /dev/video22 /dev/video23 /dev/media2 /dev/media3 rpivid (platform:rpivid): /dev/video19 /dev/media1 HD USB Camera: HD USB Camera (usb-0000:01:00.0-1.2): /dev/video0 /dev/video1 /dev/media4