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:
- Specify that the line is directly connected and
cu should not allow the driver to block
waiting for a carrier to be detected.
- Specify the line to use. Either of the forms like
/dev/cua00 are permitted. The default is
information on terminal devices. Users in group “dialer” are
permitted to use
cua(4) devices by
- Set the speed of the connection. The default is 9600.
to retrieve the dc
(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
- 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
- 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
- Stop cu (only available with
- 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
- Deassert the data terminal ready (DTR) line briefly.
- 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.
- Change the speed of the connection.
- Send a file with the XMODEM protocol.
- Get a summary of the tilde escapes.
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.
guards against multiple users connecting to a
remote system by opening modems and terminal lines with exclusive access.
- The default value for host
if none is specified via the command line.
- A system description, or an absolute path to a
- host description file
utility exits 0 on success,
and >0 if an error occurs.
command appeared in
. This version was written for
by Nicholas Marriott.