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\"     @(#)rmt.8        6.5 (Berkeley) 3/16/91
\"
Dd March 16, 1991
Dt RMT 8
Os BSD 4.2
Sh NAME
Nm rmt
Nd remote magtape protocol module
Sh SYNOPSIS
Nm rmt
Sh DESCRIPTION
Nm Rmt
is a program used by the remote dump and restore programs
in manipulating a magnetic tape drive through an interprocess
communication connection.
Nm Rmt
is normally started up with an
Xr rexec 3
or
Xr rcmd 3
call.
Pp
The
Nm rmt
program accepts requests specific to the manipulation of
magnetic tapes, performs the commands, then responds with
a status indication.  All responses are in
Tn ASCII
and in
one of two forms.
Successful commands have responses of:
Bd -filled -offset indent
Sm off
Sy A Ar number No \en
Sm on
Ed
Pp
Ar Number
is an
Tn ASCII
representation of a decimal number.
Unsuccessful commands are responded to with:
Bd -filled -offset indent
Sm off
Xo Sy E Ar error-number
No \en Ar error-message
No \en
Xc
Sm on
Ed
Pp
Ar Error-number
is one of the possible error
numbers described in
Xr intro 2
and
Ar error-message
is the corresponding error string as printed
from a call to
Xr 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
Ql \en
indicates that a newline should be supplied:
Bl -tag -width Ds
Sm off
It Xo Sy \&O Ar device
No \en Ar mode No \en
Xc
Open the specified
Ar device
using the indicated
Ar mode .
Ar Device
is a full pathname and
Ar mode
is an
Tn ASCII
representation of a decimal
number suitable for passing to
Xr open 2 .
If a device had already been opened, it is
closed before a new open is performed.
It Xo Sy C Ar device No \en
Xc
Close the currently open device.  The
Ar device
specified is ignored.
It Xo Sy L
Ar whence No \en
Ar offset No \en
Xc
Sm on
Perform an
Xr lseek 2
operation using the specified parameters.
The response value is that returned from the
Xr lseek
call.
Sm off
It Sy W Ar count No \en
Sm on
Write data onto the open device.
Nm Rmt
reads
Ar count
bytes from the connection, aborting if
a premature end-of-file is encountered.
The response value is that returned from
the
Xr write 2
call.
Sm off
It Sy R Ar count No \en
Sm on
Read
Ar count
bytes of data from the open device.
If
Ar count
exceeds the size of the data buffer (10 kilobytes), it is
truncated to the data buffer size.
Nm rmt
then performs the requested
Xr read 2
and responds with
Sm off
Sy A Ar count-read No \en
Sm on
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.
Sm off
It Xo Sy I Ar operation
No \en Ar count No \en
Xc
Sm on
Perform a
Dv MTIOCOP
Xr ioctl 2
command using the specified parameters.
The parameters are interpreted as the
Tn ASCII
representations of the decimal values
to place in the
Ar mt_op
and
Ar mt_count
fields of the structure used in the
Xr ioctl
call.  The return value is the
Ar count
parameter when the operation is successful.
It Sy S
Return the status of the open device, as
obtained with a
Dv MTIOCGET
Xr 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).
El
Sm on
Pp
Any other command causes
Nm rmt
to exit.
Sh DIAGNOSTICS
All responses are of the form described above.
Sh SEE ALSO
Xr rcmd 3 ,
Xr rexec 3 ,
Xr mtio 4 ,
Xr rdump 8 ,
Xr rrestore 8
Sh BUGS
People tempted to use this for a remote file access protocol
are discouraged.
Sh HISTORY
The
Nm
command appeared in
Bx 4.2 .

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