The Ftape Installation and Usage Guide
C
struct mtop op = { MTBSR, COUNT }; result = ioctl(tapefd, MTIOCTOP, &op);
Backward space over COUNT tape blocks (block-size is set via `MTSETBLK', See MTSETBLK).
MTSETBLK
See MTFSR.
MTBSR was unimplemented for ftape-2.x resp. sftape. For more information. See MTFSR.
MTBSR
COUNT set to `5', i.e. skip backwards over 5 tape blocks with ftape-3.04d (and later versions):
5
mt -f /dev/nqft0 bsr 5