Rmt
is a program used by 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.
The
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:
-filled -offset indent
A Ar number No \en
Number
is an
ASCII
representation of a decimal number.
Unsuccessful commands are responded to with:
-filled -offset indent
Sy E Ar error-number
\en Ar error-message
\en
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
\en
indicates that a newline should be supplied:
-tag -width Ds
Xo Sy O Ar device
\en Ar mode No \en
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.
Xo Sy C Ar device No \en
Close the currently open device. The
device
specified is ignored.
Xo Sy L
whence No \en
offset No \en
Perform an
lseek 2
operation using the specified parameters.
The response value is that returned from the
lseek
call.
Sy W Ar count No \en
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.
Sy R Ar count No \en
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 Ar count-read No \en
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.
Xo Sy I Ar operation
\en Ar count No \en
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.
1i
Sy 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
to exit.
