NAME

     mt - magnetic tape control


SYNOPSIS

     mt [-f device] [count]


DESCRIPTION

     Mt is  a  user  interface  to  the  magnetic  tape  commands
     described  in  mtio(4).   It allows one to space a tape for-
     wards or backwards, write end of file markers, etc.

     With the -f option a tape device can be named, otherwise the
     environment variable TAPE is used if set.  Standard input is
     used if the tape name is a dash (-).  The count argument  is
     used  to  tell how many blocks or files to space or how many
     file markers to write.  It may be a C-style  decimal,  octal
     or hexadecimal constant, by default "1".

     Command is the action to perform, it may be one of the  fol-
     lowing, or any unambiguous prefix (like st for status):

     eof, weof      Write count end-of-file markers.

     fsf            Forward space count file markers.

     fsr            Forward space count records.  (The size of  a
                    record  depends  on the tape, and may even be
                    variable,  depending  on  the  size  of   the
                    writes.)

     bsf            Backwards space count files.  The  count  may
                    be  zero  to  backspace  to  the start of the
                    current file.  (A tape device need  not  sup-
                    port  backwards movement, or may be very slow
                    doing it.  Rewinding and forward spacing  may
                    be better.)

     bsr            Backwards space count records.  The  tape  is
                    positioned after the last block of the previ-
                    ous file if you hit a filemark  when  spacing
                    backwards.   The  block count is set to -1 to
                    indicate that the driver has no idea where it
                    is on the previous file.

     eom            Forward space to the end of media.

     rewind         Rewind the tape.

     offline, rewoffl
                    Rewind and take offline.  This may cause some
                    drives to eject the tape.

     status         Shows the status of the drive, the sense  key
                    of  the last SCSI error, current file number,
                    current record number, residual count if  the
                    last  command  that  encountered end-of-file,
                    and the current block size.

     retension      Removes tape tension by winding and rewinding
                    the tape completely.

     erase          Erases the tape completely and rewinds it.

     density        Sets the density code to read  or  write  the
                    tape   to  count.   Density  codes  supported
                    depend on the drive.  This command  need  not
                    be  used  if the drive senses the proper den-
                    sity on read and can only write one density.

     blksize, blocksize
                    Sets the block size used to read or write the
                    tape  to  count.  This command may be used to
                    select a fixed  block  size  for  a  variable
                    block  size tape.  This will speed up I/O for
                    small block sizes.  Use a zero count  to  use
                    variable sized blocks again.


ENVIRONMENT

     TAPE           Tape drive to use if set.


FILES

     /dev/nrst4     Default tape device.


SEE ALSO

     mtio(4), st(4).


AUTHOR

     Kees J. Bot (kjb@cs.vu.nl)