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RMT(8) | System Manager's Manual | RMT(8) |
NAME¶
rmt
—
remote magtape protocol module
SYNOPSIS¶
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 commands 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 specifieddeviceusing the indicated mode.Deviceis a full pathname and modeis anASCIIrepresentation 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. Thedevice specified 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; otherwise an error in the standard format is returned. If the read was successful, the data read is then sent. - Ioperation\ncount\n
- Perform a
MTIOCOP
ioctl(2) command using the specified parameters. The parameters are interpreted as the ASCII representations of the decimal values to place in the mt_op and mt_count fields of the structure used in the ioctl call. The return value is the count parameter when the operation is successful. - S
- Return the status of the open device, as obtained with a
MTIOCGET
ioctl call. If the operation was successful, an ``ack'' is sent with the size of the status buffer, then the status buffer is sent (in binary).
rmt
to exit.
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¶
Thermt
command appeared in
4.2BSD.December 11, 1993 | BSD 4.2 |