rmt-tar

     rmt

DESCRIPTION
     Rmt is a program used by tar, cpio, mt, and the remote dump and restore
     programs in manipulating a magnetic tape drive through an interprocess
     communication connection.  Rmt is normally started up with an rexec(3) or
     rcmd(3) call or the rsh(1) command.

     The rmt program accepts requests specific to the manipulation of magnetic
     tapes, performs the commands, then responds with a status indication.
     All responses are in ASCII and in one of two forms.  Successful commands
     have responses of:

           Anumber\n

     Number is an ASCII representation of a decimal number.  Unsuccessful com-
     mands are responded to with:

           Eerror-number\nerror-message\n

     Error-number is one of the possible error numbers described in intro(2)
     and error-message is the corresponding error string as printed from a
     call to perror(3).  The protocol is comprised of the following commands,
     which are sent as indicated - no spaces are supplied between the command
     and its arguments, or between its arguments, and '\n' indicates that a
     newline should be supplied:

     Odevice\nmode\n
             Open the specified deviceusing the indicated mode.Deviceis a full
             pathname and modeis an ASCIIrepresentation of a decimal number
             suitable for passing to open(2).If a device had already been
             opened, it is closed before a new open is performed.

     Cdevice\n
             Close the currently open device.  The devicespecified is ignored.

     Loffset\nwhence\n
             Perform an lseek(2) operation using the specified parameters.
             The response value is that returned from the lseek call.

     Wcount\n
             Write data onto the open device.  Rmt reads count bytes from the
             connection, aborting if a premature end-of-file is encountered.
             The response value is that returned from the write(2) call.

     Rcount\n
             Read count bytes of data from the open device.  If count exceeds
             the size of the data buffer (10 kilobytes), it is truncated to
             the data buffer size.  rmt then performs the requested read(2)
             and responds with Acount-read\n if the read was successful; oth-
             erwise an error in the standard format is returned.  If the read
             was successful, the data read is then sent.

     Ioperation\ncount\n

DIAGNOSTICS
     All responses are of the form described above.

SEE ALSO
     tar(1), cpio(1), mt(1), rsh(1), rcmd(3), rexec(3), mtio(4), rdump(8),
     rrestore(8)

BUGS
     People should be discouraged from using this for a remote file access
     protocol.

HISTORY
     The rmt command appeared in 4.2BSD.

4.2 Berkeley Distribution      December 11, 1993     4.2 Berkeley Distribution
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