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MTIO(4)                    Kernel Interfaces Manual                    MTIO(4)

       mtio - magnetic tape commands

       #include <sys/types.h>
       #include <sys/mtio.h>
       #include <sys/ioctl.h>

       The  magnetic  tape  devices described in sd(4) may be sent commands or
       queried for their status using the following ioctl calls:

              ioctl(fd, MTIOCTOP, &struct mtop)
              ioctl(fd, MTIOCGET, &struct mtget)

       The struct mtop, struct mtget and associated definitions are defined in
       <sys/mtio.h> as follows:

       /* Tape operations: ioctl(fd, MTIOCTOP, &struct mtop) */

       struct mtop {
           short  mt_op;         /* Operation (MTWEOF, etc.) */
           int    mt_count;      /* Repeat count. */

       #define MTWEOF   0    /* Write End-Of-File Marker */
       #define MTFSF    1    /* Forward Space File mark */
       #define MTBSF    2    /* Backward Space File mark */
       #define MTFSR    3    /* Forward Space Record */
       #define MTBSR    4    /* Backward Space Record */
       #define MTREW    5    /* Rewind tape */
       #define MTOFFL   6    /* Rewind and take Offline */
       #define MTNOP    7    /* No-Operation, set status only */
       #define MTRETEN  8    /* Retension (completely wind and rewind) */
       #define MTERASE  9    /* Erase the tape and rewind */
       #define MTEOM    10   /* Position at End-Of-Media */
       #define MTMODE   11   /* Select tape density */
       #define MTBLKZ   12   /* Select tape block size */

       /* Tape status: ioctl(fd, MTIOCGET, &struct mtget) */

       struct mtget {
           short  mt_type;       /* Type of tape device. */

           /* Device dependent "registers". */
           short  mt_dsreg;      /* Drive status register. */
           short  mt_erreg;      /* Error register. */

           /* Misc info. */
           off_t  mt_resid;      /* Residual count. */
           off_t  mt_fileno;     /* Current File Number. */
           off_t  mt_blkno;      /* Current Block Number within file. */
           off_t  mt_blksize;    /* Current block size. */

       See  mt(1) for a detailed description on what each operation does.  The
       mt_type field is always zero, there is no use for it yet.  Mt_dsreg  is
       0  (OK),  1  (Error),  or 2 (EOF encountered.)  Mt_erreg holds the SCSI
       sense key of the last operation.  Mt_blksize is the current tape  block
       size in bytes, zero if the block size is variable.

       Note  that one can issue these commands on a file descriptor that is in
       use to read or write data, something that mt can't do.  So you can  add
       eof  markers  in the middle of an output stream, or get the status of a
       device before a rewind-on-close tape rewinds.

       The driver will automatically add an end of file marker to a tape  that
       is written to if you execute a space command.  If you write eof markers
       yourself then the driver will not add one extra on close.

       mt(1), sd(4).

       Kees J. Bot (