man(1) Manual page archive


     TM(4)                                                       TM(4)

     NAME
          tm - TM-11/TU-10 magtape interface

     DESCRIPTION
          The files mt0, ..., mt7 refer to the DEC TU10/TM11 magtape.
          When closed it can be rewound or not, see below.  If it was
          open for writing, two end-of-files are written.  If the tape
          is not to be rewound it is positioned with the head between
          the two tapemarks.

          If the 0200 bit is on in the minor device number the tape is
          not rewound when closed.

          A standard tape consists of a series of 512 byte records
          terminated by an end-of-file.  To the extent possible, the
          system makes it possible, if inefficient, to treat the tape
          like any other file.  Seeks have their usual meaning and it
          is possible to read or write a byte at a time.  Writing in
          very small units is inadvisable, however, because it tends
          to create monstrous record gaps.

          The mt files discussed above are useful when it is desired
          to access the tape in a way compatible with ordinary files.
          When foreign tapes are to be dealt with, and especially when
          long records are to be read or written, the `raw' interface
          is appropriate.  The associated files are named rmt0, ...,
          rmt7. Each read or write call reads or writes the next
          record on the tape.  In the write case the record has the
          same length as the buffer given.  During a read, the record
          size is passed back as the number of bytes read, provided it
          is no greater than the buffer size; if the record is long,
          an error is indicated.  In raw tape I/O, the buffer must
          begin on a word boundary and the count must be even.  Seeks
          are ignored.  A zero byte count is returned when a tape mark
          is read, but another read will fetch the first record of the
          new tape file.

     FILES
          /dev/mt?, /dev/rmt?

     SEE ALSO
          tp(1)

     BUGS
          If any non-data error is encountered, it refuses to do any-
          thing more until closed.  In raw I/O, there should be a way
          to perform forward and backward record and file spacing and
          to write an EOF mark.