rmt - remote magnetic tape server
provides remote access to files and devices for tar
(1), and similar backup utilities. It is normally called by running
(1) or ssh
(1) to the remote machine, optionally using a
different login name if one is supplied.
The calling program communicates with rmt
by sending requests on its
standard input and reading replies from the standard output. A request
consists of a request letter followed by an argument (if required) and a
newline character. Additional data, if any, are sent after the newline. On
is an ASCII representation of a decimal return code.
Additional data are returned after this line. On error, the following response
is one of the system error codes, as described in
(3), and error-message
is a one-line human-readable
description of the error, as printed by perror
Available commands and possible responses are discussed in detail in the
- Opens the device with given flags. If a
device had already been opened, it is closed before opening the new one.
- The name of the device to open.
- Flags for open(2): a decimal number, or any valid
O_* constant from fcntl.h (the initial O_ may be
omitted), or a bitwise or (using |) of any number of these, e.g.:
In addition, a combined form is also allowed,
i.e. a decimal mode followed by its symbolic representation. In this case the
symbolic representation is given preference.
A0\n on success.
BSD version allows only decimal number as
- Close the currently open device.
Any arguments are silently ignored.
A0\n on success.
Performs an lseek
(2) on the currently
open device with the specified parameters.
- Where to measure offset from. Valid values are:
0, SET, SEEK_SET seek from the file beginning
1, CUR, SEEK_CUR seek from the current location
2, END, SEEK_END seek from the file end
Aoffset\n on success. The offset is the new
offset in file.
- BSD version allows only 0,1,2 as whence.
Read count bytes of data from the current device.
- number of bytes to read.
followed by rdcount bytes of data read from the device.
- Writes data onto the current device. The command is
followed by count bytes of input data.
- Number of bytes to write.
On success: Awrcount\n, where wrcount is the
number of bytes actually written.
- Perform a MTIOCOP ioctl(2) command with the
- MTIOCOP operation code.
On success: A0\n.
- Returns the status of the currently open device, as
obtained from a MTIOCGET ioctl(2) call.
On success: Acount\n followed by count bytes of
Using this utility as a general-purpose remote file access tool is discouraged.
Report bugs to <email@example.com>.
command appeared in 4.2BSD. The GNU rmt
is written from
scratch, using the BSD specification.
Copyright © 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it. There is NO
WARRANTY, to the extent permitted by law.