cu —
serial terminal emulator
cu |
[ -dr
]
[-l
line
]
[-s
speed |
-
speed
] |
cu is used to connect to another system over
a serial link. In the era before modern networks, it was typically used to
connect to a modem in order to dial in to a remote host. It is now frequently
used for tasks such as attaching to the serial console of another machine for
administrative or debugging purposes.
The options are as follows:
-
-
-d- Specify that the line is directly connected and
cu should not allow the driver to block
waiting for a carrier to be detected.
-
-
-l
line- Specify the line to use. Either of the forms like
cua00 or
/dev/cua00 are permitted. The default
is /dev/cua00. See
cua(4) for information on
terminal devices. Users in group “dialer” are permitted to
use cua(4) devices by
default.
-
-
-r- Start
cu in restricted mode. This
prevents all local filesystem operations
(~R,
~X, and
~>) and command executions
(~C and
~$).
-
-
-s
speed |
-
speed- Set the speed of the connection. The default is 9600.
If
host is given,
cu uses the
remote(5) database to retrieve
the
dc (directly connected),
dv (device) and
br
(baud rate) capabilities for that host. The
cu utility ignores other capabilities found
in that database.
Typed characters are normally transmitted directly to the remote machine (which
does the echoing as well). A tilde (‘
~’)
appearing as the first character of a line is an escape signal; the following
are recognized:
-
-
~^D
or ~.- Drop the connection and exit. Only the connection is dropped – the
login session is not terminated.
-
-
~>- Copy file from local to remote.
cu
prompts for the name of a local file to transmit.
-
-
~$- Pipe the output from a local UNIX process to the
remote host. The command string sent to the local
UNIX system is processed by the shell.
-
-
~#- Send a
BREAK to the remote system.
-
-
~^Z- Stop
cu (only available with job
control).
-
-
~C- Fork a child process on the local system to perform special protocols such
as XMODEM. The child program will be run with the following arrangement of
file descriptors:
0 <-> remote tty in
1 <-> remote tty out
2 <-> local tty stderr
-
-
~D- Deassert the data terminal ready (DTR) line briefly.
-
-
~R- Record all output from the remote system to a file. If the given file
already exists, it is appended to. If no file is specified, any existing
recording is stopped.
-
-
~S- Change the speed of the connection.
-
-
~X- Send a file with the XMODEM protocol.
-
-
~?- Get a summary of the tilde escapes.
When
cu prompts for an argument, for example
during setup of a file transfer, the line typed may be edited with the
standard erase and kill characters. A null line in response to a prompt, or an
interrupt, will abort the dialogue and return the user to the remote machine.
cu guards against multiple users connecting
to a remote system by opening modems and terminal lines with exclusive access.
-
-
HOST- The default value for host if none is
specified via the command line.
-
-
REMOTE- A system description, or an absolute path to a
remote(5) system description
database.
-
-
- /etc/remote
- host description file
The
cu utility exits 0 on success,
and >0 if an error occurs.
remote(5)
The
cu command appeared in
4.2BSD. This version was written for
OpenBSD 5.4 by Nicholas Marriott.
![[OpenBSD]](/openbsd.gif){kind=small}