cu(C)

Syntax

cu [ -dht ] [ -l line ] [ -o | -e | -oe ] [ -s speed ] [ -x n ] -n

cu [ -dht ] [ -o | -e | -oe ] [ -s speed ] [ -x n ] -l line [ dir ]

cu [ -dht ] [ -o | -e | -oe ] [ -x n ] systemname

Description

cu accepts the following options and arguments:

-s speed

Specifies the transmission speed (150, 300, 600, 1200, 2400, 4800, 9600, 19200, 38400). The default value is ``Any'' speed which will depend on the order of the lines in the /usr/lib/uucp/Devices file. A speed range can also be specified (for example, -s 1200-4800).

-l line

Specifies a device name to use as the communication line. This can be used to override the search that would otherwise take place for the first available line having the right speed. When the -l option is used without the -s option, the speed of a line is taken from the Devices file. When the -l and -s options are both used together, cu will search the Devices file to check if the requested speed for the requested line is available. If so, the connection will be made at the requested speed; otherwise, an error message will be printed and the call will not be made. The specified device is generally a directly connected asynchronous line (for example, /dev/ttyab) in which case a telephone number (telno) is not required. The specified device need not be in the /dev directory. If the specified device is associated with an auto dialer, a telephone number must be provided. Use of this option with systemname rather than telno will not give the desired result (see systemname below).

-d

Enables diagnostic tracing.

-h

Emulates local echo, supporting calls to other computer systems which expect terminals to be set to half-duplex mode.

-t

Used to dial an ASCII terminal which has been set to auto answer. Appropriate mapping of carriage-return to carriage-return-line-feed pairs is set.

-x n

Causes diagnostic traces to be printed; it produces a detailed output of the program execution on stderr. The debugging level, n, is a single digit in the range 0 to 9; -x 9 is the most useful value.

-n

For added security, -n will prompt the user to provide the telephone number to be dialed rather than taking it from the command line.

telno

When using an automatic dialer, the argument is the telephone number with equal signs for secondary dial tone or minus signs placed appropriately for delays of 4 seconds.

systemname

A UUCP system name may be used rather than a telephone number. In this case, cu will obtain an appropriate direct line or telephone number from /usr/lib/uucp/Systems. Note: the systemname option should not be used in conjunction with the -l and -s options as cu will connect to the first available line for the system name specified, ignoring the requested line and speed.

dir

The keyword dir can be used with cu -l line, in order to talk directly to a modem on that line, instead of talking to another system via that modem. This can be useful when debugging or checking modem operation. Note: only users with write access to the Devices file are permitted to use cu -l line dir.

In addition, cu uses the following options to determine communications settings:

-o

the remote system expects or sends 7-bits with odd parity

-e

the remote system expects or sends 7-bits with even parity

-oe

the remote system expects or sends 7-bits, ignoring parity and sends 7-bits with either parity

After making the connection, cu runs as two processes: the transmit process and the receive process. The transmit process reads data from standard input and, except for lines beginning with ``~'', passes the data to the remote system. The receive process accepts data from the remote system and, except for lines beginning with ``~'', passes the data to standard output.

Normally, an automatic XON/XOFF protocol is used to control input from the remote system so the buffer is not overrun.

Lines beginning with ``~'' have special meanings.

The transmit process interprets the following user-initiated commands:

~.

Terminate the conversation.

~!

Escape to an interactive shell on the local system.

~!cmd ...

Run cmd on the local system (via sh -c).

~$cmd ...

Run cmd locally and send its output to the remote system.

~+cmd ...

Run cmd on the local system but take standard input from the remote system.

~%cd

Change the directory on the local system. Note: ~!cd will cause the command to be run by a sub-shell, probably not what was intended.

~%take there_name [ here_name ]

Copy file there_name on the remote system to file here_name on the local system. If here_name is omitted, the pathname there_name on the remote system is used by default.

~%put here_name [ there_name ]

Copy file here_name on the local system to file there_name on the remote system. If there_name is omitted, the pathname here_name on the local system is used by default.

For both ~%take and ~%put commands, as each block of the file is transferred, consecutive single digits are printed to the terminal

~~line

Send the line ~line to the remote system.

~%b
~%break

Transmit a BREAK to the remote system.

~%d
~%debug

Toggles the -x debugging level between 0 and 9.

~t

Prints the values of the termio structure variables for the user's terminal (useful for debugging).

~l

Prints the values of the termio structure variables for the remote communication line (useful for debugging).

~%nostop

Toggles between XON/XOFF input control protocol and no input control. This is useful in case the remote system is one which does not respond properly to the XON and XOFF characters.

The use of ~%take requires the existence of echo(C) and cat on the remote system. Also, tabs mode (see stty(C)) should be set on the remote system if tabs are to be copied without expansion to spaces.

The receive process normally copies data from the remote system to its standard output. It may also direct output to local files.

You can construct take and put commands that work between UNIX and non-UNIX systems by sending the appropriate characters to cu. To do this, you will need to know the equivalent of echo and cat on the non-UNIX system.

For example, to transfer a file named fred from a remote non-UNIX system to the file /tmp/fred on the local UNIX system, construct a command similar to the following:

   ~%
   echo '~>':/tmp/fred
   cat fred
   echo '~>'

You can also append the file from the remote machine to an existing file on the local system:

   ~%
   echo '~>>':/tmp/fred
   cat fred
   echo '~>'

When cu is used on system1 to connect to system2 and subsequently used on system2 to connect to system3, commands on system2 can be executed by using ``~~''. Executing a tilde command reminds the user of the local system uname. For example, uname can be executed on systems 1, 2, and 3 as follows:

   uname
   system3
   ~!uname
   system1
   ~~!uname
   system2

Exit values

Examples

If the speed is not specified, ``Any'' is the default value.

To login to a system connected by a direct line:

cu -l /dev/ttyXX or cu -l ttyXX

To dial a system with the specific line and a specific speed:

cu -s 1200 -l ttyXX

To dial a system using a specific line associated with an auto dialer:

cu -l ttyXX 9=2015551212

To call up a system named jimmy:

cu jimmy

To talk directly to an ACU (connect directly with the modem and enter modem commands manually):

cu -l ttyXX dir

Warning

Limitations

Files

/usr/spool/uucp/LCK..tty

lock file for tty device

See also

Standards conformance

ISO/IEC DIS 99452:1992, Information technology Portable Operating System Interface (POSIX) Part 2: Shell and Utilities (IEEE Std 1003.21992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992.