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CU(1C)									CU(1C)

NAME    [Toc]    [Back]

     cu	- call another UNIX system

SYNOPSIS    [Toc]    [Back]

     cu	[options]  [-s speed]	-l line
     cu	[options]  [-s speed]  [-l line] [-n] telno
     cu	[options]  systemname

     where options can be any of:
	 [-h]  [-d]  [-o | -e]	[-c class]

DESCRIPTION    [Toc]    [Back]

     cu	calls up another UNIX system, a	terminal, or possibly a	non-UNIX
     system.  It manages an interactive	conversation with possible transfers
     of	ASCII files.

     cu	accepts	the following options and arguments:

     -sspeed	 Specifies the transmission speed (300,	1200, 2400, 4800,
		 9600);	The default value is "Any" speed which will depend on
		 the order of the lines	in the /etc/uucp/Devices file.

     -lline	 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.  If the device is
		 not found in the Devices file,	an error message similar to


		 is printed.  The specified device is generally	a directly
		 connected asynchronous	line (e.g., /dev/ttyd4)	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.

		 A line	also used by getty(1M) cannot be used with this
		 option.  A line in use	by uugetty(1M) can be used, provided
		 the same physical device name is used by both cu and uugetty.
		 However, if uugetty(1M) is being used,	there is likely	to be
		 an autodialing	modem on the line, using an entry in the
		 Dialers file like the Hayes24 entry, and ready	to accept a
		 telephone, telno, number from the cu command.

		 Use of	this option with systemname rather than	telno will not

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CU(1C)									CU(1C)

		 give the desired result (see systemname below).

     -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 carriagereturn-line-feed
 pairs	is set.

     -d		 Causes	diagnostic traces to be	printed.

     -o		 Designates that odd parity is to be generated for data	sent
		 to the	remote system.

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

     -e		 Designates that even parity is	to be generated	for data sent
		 to the	remote system.

     -cclass	 Specifies a modem "class" such	as ACU or Direct found in the
		 Dialers file.

     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 /etc/uucp/Systems. Note that
		 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.  Note that only the telephone
		 number	will be	used from the /etc/uucp/Systems	file; the
		 chatting to log into the remote system	will not be used since
		 it is unlikely	that an	interactive user wants to start	SLIP,
		 PPP, or UUCP.

     After making the connection, cu runs as two processes:  the transmit
     process reads data	from the standard input	and, except for	lines
     beginning with ~, passes it to the	remote system; the receive process
     accepts data from the remote system and, except for lines beginning with
     ~,	passes it to the standard output.  Normally, an	automatic DC3/DC1
     protocol is used to control input from the	remote so the buffer is	not
     overrun.  Lines beginning with ~ have special meanings.

     The transmit process interprets the following user	initiated commands:

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CU(1C)									CU(1C)

     ~.			 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

     ~^Z		 suspend the cu	session.  (^Z, control-Z, is the
			 current job control suspend character (see csh(1) and

     ~%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 from [ to ]	 copy file from	(on the	remote system) to file to on
			 the local system.  If to is omitted, the from
			 argument is used in both places.  The shell commands
			 below are sent	to the remote machine to cause it to
			 transmit the file.  In	fact, they are sent in a
			 single	line with semicolons (;) between each command.

		    stty -echo
		    if test -r arg1; then
			 (echo '~>':arg2;cat arg1;echo '~>')
			 echo cant\'t open: arg1
		    stty echo

     ~%put from	[ to ]
	  copy file from (on local system) to file to on remote	system.	 If to
	  is omitted, the from argument	is used	in both	places.

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

	  The shell command line below is sent to the remote machine to	cause
	  it to	accept the data.  Obviously, the shell on the remote machine
	  must be /bin/sh or a shell that correctly interpret these commands.

		    stty -echo;(cat - >	arg2)||cat - >/dev/null;stty echo

     ~~	line
	  send the line	~ line to the remote system.

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CU(1C)									CU(1C)

	  transmit a BREAK to the remote system	(which can also	be specified
	  as ~%b).

	  toggles the -d debugging option on or	off (which can also be
	  specified as ~%d).

     ~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).

	  toggles between DC3/DC1 input	control	protocol and no	input control.
	  This is useful in case the remote system is one which	does not
	  respond properly to the DC3 and DC1 characters.

     The receive process normally copies data from the remote system to	its
     standard output.  The program accomplishes	the ~%take command by
     initiating	an output diversion to a file when a line from the remote
     begins with ~.

     Data from the remote is diverted (or appended, if >> is used) to file on
     the local system.	The trailing ~>	marks the end of the diversion.

     The use of	~%put requires stty(1) and cat(1) on the remote	side.  It also
     requires that the current erase and kill characters on the	remote system
     be	identical to these current control characters on the local system.
     Backslashes are inserted at appropriate places.

     The use of	~%take requires	the existence of echo(1) and cat(1) on the
     remote system.  Also, tabs	mode (See stty(1)) should be set on the	remote
     system if tabs are	to be copied without expansion to spaces.

     When cu is	used on	system X to connect to system Y	and subsequently used
     on	system Y to connect to system Z, commands on system Y can be executed
     by	using ~~. Executing a tilde command reminds the	user of	the local
     system uname.  For	example, uname can be executed on Z, X,	and Y as


     In	general, ~ causes the command to be executed on	the original machine,
     ~~	causes the command to be executed on the next machine in the chain.

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CU(1C)									CU(1C)

EXAMPLES    [Toc]    [Back]

     To	dial a system whose telephone number is	9 201 555 1212 using 1200 baud
     (where dialtone is	expected after the 9):
	  cu  -s1200   9=12015551212

     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

	  cu -l	ttyXX

     To	dial a system with the specific	line and a specific speed:
	  cu  -s1200  -l  ttyXX

     To	dial a system using a specific line associated with an auto dialer:
	  cu  -l  culXX	 9=12015551212

     To	use a system name:
	  cu  systemname

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     cat(1), duart(7), echo(1),	stty(1), uucp(1C), uugetty(1M),	uname(1).

DIAGNOSTICS    [Toc]    [Back]

     Exit code is zero for normal exit,	otherwise, one.

WARNINGS    [Toc]    [Back]

     The cu command does not do	any integrity checking on data it transfers.
     Data fields with special cu characters may	not be transmitted properly.
     Depending on the interconnection hardware,	it may be necessary to use a
     ~.	to terminate the conversion even if stty 0 has been used.  Nonprinting
 characters are not dependably transmitted	using either the ~%put
     or	~%take commands.  cu between an	IMBR1 and a penril modem will not
     return a login prompt immediately upon connection.	 A carriage return
     will return the prompt.

     The device	names, dialers,	and so forth in	/etc/uucp/Devices must be
     correct.  Because cu is suid-uucp,	the device used, such as /dev/ttym3,
     must be readable and writable by the "user" uucp.

BUGS    [Toc]    [Back]

     There is an artificial slowing of transmission by cu during the ~%put
     operation so that loss of data is unlikely.

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CU(1C)									CU(1C)

									PPPPaaaaggggeeee 6666
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