SMCIOC_LOAD_MEDIUM

This IOCTL command loads a tape from a specific slot into the drive. Or, it loads from the first full slot into the drive if the slot address is specified as zero.

An example of the SMCIOC_LOAD_MEDIUM command is
  #include <sys/Atape.h>

  /* load cartridge from slot 3 */
  if (ioctl (tapefd, SMCIOC_LOAD_MEDIUM,3)<0)
    {
        printf ("IOCTL failure. errno=%d\n",errno)
        exit(1):
    }

  /* load first cartridge from magazine */
  if (ioctl (tapefd, SMCIOC_LOAD_MEDIUM,0)<0)
    {
        printf ("IOCTL failure. errno=%d\n",errno)
        exit(1):
    }