How do I read drive status for a USB attached optical drive?

My long-term backups are written to M-Disc platters (100GB BD-R) through a USB-attached BD-RW drive. This works well, but I would like to be able to check if there is a blank disc inserted in the drive at the start of my backup scripts. How do I do that? - command line? - ioctl system call? And how do I decode whatever status bytes it reads out?