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UNIX in a Nutshell: System V Edition

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UNIX Commands
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Call up another UNIX system or a terminal via a direct line or a modem. A non-UNIX system can also be called.


-b n

Process lines using n -bit characters (7 or 8).

-c name

Search UUCP's Devices file and select the local area network that matches name (this assumes connection to a system).


Print diagnostics.


Send even-parity data to remote system.


Emulate local echo and support calls to other systems expecting terminals to use half duplex mode.

-l line

Communicate on line device (e.g., /dev/tty001 ).


Prompt user for a telephone number.


Use odd parity (opposite of -e ).

-s n

Set transmission rate to n (e.g., 1200, 2400, 9600 bps). Default is Any .


Dial an ASCII terminal that has auto answer set.



The telephone number of the modem to connect to.


Call the system known to uucp (run uuname to list valid system names).


An address specific to your local area network.

cu runs as two processes: transmit and receive. Transmit reads from standard input and passes lines to the remote system; receive reads data from the remote system and passes lines to standard output. Lines that begin with a tilde ( ~ ) are treated as commands and are not passed.

Transmit options


Terminate the conversation.


Escape to an interactive shell on the local system.

~! cmd ...

Run command on local system (via sh -c ).

~$ cmd ...

Run command locally; send output to remote system.


Change directory on the local system.

~%take file [ target ]

Copy file from remote system to target on the local system. If target is omitted, file is used in both places.

~%put file [ target ]

Copy file from the local system to target on the remote system. If target is omitted, file is used in both places.

~ ~ ...

Use two tildes when you want to pass a line that begins with a tilde. This lets you issue commands to more than one system in a cu chain. For example, use ~~. to terminate the conversation on a second system cu 'd to from the first.


Send a BREAK sequence to remote system.


Turn debug mode on or off.


Print termio structure for local terminal.


Print termio structure for communication line.


Turn on/off the DC3/DC1 XON/XOFF control protocol (characters ^S, ^Q) for the remainder of the session (formerly ~%nostop , which is still valid).


Set output flow control either on or off.


Allow/prevent diversions not specified by ~%take .


Allow/prevent old-style syntax for diversions received.


Connect to terminal line /dev/ttya at 1200 baud:

cu -s1200 -l/dev/ttya

Connect to modem with phone number 555-9876:

cu 5559876

Connect to system named usenix :

cu usenix

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