is a program used by tar, cpio, mt, and the remote dump and restore
programs in manipulating a magnetic tape drive through an interprocess
is normally started up with an
call or the
program accepts requests specific to the manipulation of
magnetic tapes, performs the commands, then responds with
a status indication. All responses are in
one of two forms.
Successful commands have responses of:
A number \n
representation of a decimal number.
Unsuccessful commands are responded to with:
Sy E Ar error-number
is one of the possible error
numbers described in
is the corresponding error string as printed
from a call to
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
indicates that a newline should be supplied:
O device\n mode \n
Open the specified
using the indicated
is a full pathname and
representation of a decimal
number suitable for passing to
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
specified is ignored.
Loffset \nwhence \n
operation using the specified parameters.
The response value is that returned from the
W count \n
Write data onto the open device.
bytes from the connection, aborting if
a premature end-of-file is encountered.
The response value is that returned from
R count \n
bytes of data from the open device.
exceeds the size of the data buffer (10 kilobytes), it is
truncated to the data buffer size.
then performs the requested
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
command using the specified parameters.
The parameters are interpreted as the
representations of the decimal values
to place in the
fields of the structure used in the
call. The return value is the
parameter when the operation is successful.
Return the status of the open device, as
obtained with a
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).