mtio(7)                                                   mtio(7)



NAME
     mtio - interface for magnetic tape devices

DESCRIPTION
     The mtio interface gives applications access to tape devices
     through a standard interface.

     While general read, write, and seek operations are part of
     the standard I/O library, additional resources are required
     to support tape devices.  The mtio interface provides a
     fairly device-independent way to perform additional
     operations, such as rewinding, that are common to tape
     drives but not common to other types of devices.  One
     feature of the mtio interface is that it reads and writes
     only in terms of the appropriate block size for the tape
     device.  This ``blocking'' of data is a requirement for
     minidatacartridge drives such as the Apple Tape Backup 40SC
     (but not DDS-DC DAT drives). To ensure that data is properly
     blocked for minidatacartridge drives, use the tcb filter
     (see tcb(1), dd(1), and tc(7)).

     The mtio interface moderates device I/O when output is sent
     to or obtained from the tape device files in /dev/rmt.

I/O Controls
     When you manipulate the tape cartridge device directly
     through your own programs or through programs such as mt,
     tape-specific operations are supported through mtio I/O
     controls (ioctls).  With a few exceptions, these generic
     operations are shared by all tape drives.  One exception is
     the ``format'' ioctl (MTFORMAT), which is available for the
     Apple Tape Backup 40SC and DDS-DC DAT drives; in general,
     MTFORMAT is not useful for reel tape drives, such as nine-
     track tape drives.  Other peculiarities of minidatacartridge
     drives are described in tc(7).  The following is a list of
     mtio ioctls and their associated subcommands.  For complete
     details about the data structures, see <sys/mtio.h>.

     ioctl(fildes, MTIOCGET, *mtget)
          This tape ioctl causes the tape unit to return the
          status of the tape drive in mtget.

     ioctl(fildes, MTIOCTOP, *mtop)
          This tape ioctl causes the tape unit to perform the
          subcommand selected by the current values stored in the
          structure mtop.

          Here are the subcommands for MTIOCTOP:

          MTWEOF
               Writes an end-of-file record.




March 1993                                                      1

mtio(7)                                                   mtio(7)



          MTFSF
               Moves the tape media forward one file.

          MTBSF
               Moves the tape media backward one file.

          MTFSR
               Moves the tape media forward one record.

          MTBSR
               Moves the tape media backward one record.

          MTREW
               Rewinds the tape.

          MTOFFL
               Rewinds the tape and puts the drive offline.

          MTNOP
               Sets status, but performs no operation.

FILES
     /dev/rmt/*
          Raw magnetic tape device files
     /usr/lib/sys/ioctl.h
          Header file
     /usr/lib/sys/mtio.h
          Header file
SEE ALSO
     tc(7)

     mt(1), tar(1), tcb(1), tp(1) in A/UX Command Reference























2                                                      March 1993