RMT
Section: Maintenance Commands (8)
BSD mandoc
BSD 4.2
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:
A number \n
Number
is an
ASCII
representation of a decimal number.
Unsuccessful commands are responded to with:
Sy E Ar error-number
\n error-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:
-
O device
\n mode \n
-
- Open the specified
device
using the indicated
mode
Device
is a full pathname and
mode
is an
ASCII
representation 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.
-
C device \n
-
- Close the currently open device. The
device
specified is ignored.
-
L
offset \n
whence \n
-
- Perform an
lseek(2)
operation using the specified parameters.
The response value is that returned from the
lseek
call.
- W count \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.
- R count \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
A count-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.
-
I operation
\n count \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).
Any other command causes
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
The
rmt
command appeared in
BSD 4.2
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- DIAGNOSTICS
-
- SEE ALSO
-
- BUGS
-
- HISTORY
-
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Time: 07:35:41 GMT, March 26, 2013