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cu(1C)			    Communication Commands			cu(1C)

NAME
       cu - call another UNIX system

SYNOPSIS
       cu  [-c device | -l line]  [-s speed] [-b bits] [-h] [-n] [-t] [-d] [-o
       | -e]  [-L] [-C] [-H]  telno | systemname [local-cmd]

DESCRIPTION
       The command cu calls up another UNIX system, a terminal, or possibly  a
       non-UNIX	 system.  It manages an interactive conversation with possible
       transfers of files. It is convenient to think of cu as operating in two
       phases. The first phase is the connection phase in which the connection
       is established. cu then enters the conversation phase. The -d option is
       the only one that applies to both phases.

OPTIONS
       cu  accepts  many  options.  The	 -c, -l, and -s options play a part in
       selecting the medium. The remaining options are used in configuring the
       line.

       -b bits	       Forces  bits  to be the number of bits processed on the
		       line. bits is either  7 or 8.  This  allows  connection
		       between	systems	 with  different  character sizes.  By
		       default, the character size of the line is set  to  the
		       same value as the current local terminal, but the char‐
		       acter size setting is affected by LC_CTYPE also.

       -c device       Forces cu to use only entries in the "Type" field  (the
		       first  field  in the /etc/uucp/Devices file) that match
		       the user specified device, usually the name of a	 local
		       area network.

       -C	       Runs  the local-cmd specified at the end of the command
		       line instead of entering interactive  mode.  The	 stdin
		       and  stdout  of	the  command  that is run refer to the
		       remote connection.

       -d	       Prints diagnostic traces.

       -e	       Sets an EVEN data parity.  This option designates  that
		       EVEN  parity  is	 to  be generated for data sent to the
		       remote system.

       -h	       Sets communication mode to  half-duplex.	  This	option
		       emulates	 local echo in order to support calls to other
		       computer systems that expect terminals  to  be  set  to
		       half-duplex mode.

       -H	       Ignores	one  hangup. This allows the user to remain in
		       cu while the remote machine disconnects	and  places  a
		       call  back to the local machine.	 This option should be
		       used when connecting to systems with callback or	 dial‐
		       back   modems.  Once  the  callback  occurs  subsequent
		       hangups will cause cu to terminate.  This option can be
		       specified  more	than  once. For more information about
		       dialback configuration, see remote(4) and System Admin‐
		       istration Guide: IP Services

       -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	 /etc/uucp/Devices file record in  which  line
		       matches	the second field (the Line field). When the -l
		       and -s options are both used together, cu  will	search
		       the  /etc/uucp/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, other‐
		       wise, an error message will be  printed	and  the  call
		       will  not  be made.  In the general case where a speci‐
		       fied device is a directly connected  asynchronous  line
		       (for   instance,	  /dev/term/a),	  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.

       -L	       Goes  through  the login chat sequence specified in the
		       /etc/uucp/Systems file. For more information about  the
		       chat sequence, see System Administration Guide: IP Ser‐
		       vices

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

       -o	       Sets  an	 ODD data parity.  This option designates that
		       ODD parity is to be generated  for  data	 sent  to  the
		       remote system.

       -s speed	       Specifies  the  transmission  speed  (300,  1200, 2400,
		       4800, 9600, 19200, 38400). The default value  is	 "Any"
		       speed  which  will  depend on the order of the lines in
		       the /etc/uucp/Devices file.

       -t	       Dials a terminal which has been	set  to	 auto  answer.
		       Appropriate  mapping  of	 carriage-return  to carriage-
		       return-line-feed pairs is set.

OPERANDS
       The following operands are supported:

       telno	       When using an automatic dialler,	 specifies  the	 tele‐
		       phone  number  with equal signs for secondary dial tone
		       or minus signs placed appropriately  for	 delays	 of  4
		       seconds.

       systemname      Specifies  a uucp system name, which can be used rather
		       than a telephone number; in this case, cu  will	obtain
		       an  appropriate	direct line or telephone number from a
		       system file.

USAGE
   Connection Phase
       cu uses the same mechanism that uucp(1C) does to	 establish  a  connec‐
       tion.   This   means   that   it	  will	use  the  uucp	control	 files
       /etc/uucp/Devices and /etc/uucp/Systems. This gives cu the  ability  to
       choose  from  several  different media to establish the connection. The
       possible media include telephone lines, direct connections,  and	 local
       area  networks  (LAN).  The  /etc/uucp/Devices  file contains a list of
       media that are available on your	 system.  The  /etc/uucp/Systems  file
       contains	 information  for  connecting to remote systems, but it is not
       generally readable.

       Note: cu determines which /etc/uucp/Systems and /etc/uucp/Devices files
       to  use based upon the name used to invoke cu. In the simple case, this
       name will be "cu", but you could also have created a link  to  cu  with
       another	name,  such as "pppcu", in which case cu would then look for a
       "service=pppcu" entry in	 the   /etc/uucp/Sysfiles  file	 to  determine
       which /etc/uucp/Systems file to use.

       The telno or systemname parameter from the command line is used to tell
       cu what system you wish to connect to. This parameter can be  blank,  a
       telephone number, a system name, or a LAN specific address.

       telephone number	       A  telephone  number  is a string consisting of
			       the tone dial characters (the digits  0 through
			       9,  *, and #) plus the special characters = and
			       −. The equal sign designates a  secondary  dial
			       tone  and  the  minus  sign creates a  4 second
			       delay.

       system name	       A system name is the name of any computer  that
			       uucp  can call; the uuname(1C) command prints a
			       list of these names.

       LAN address	       The documentation for your  LAN will  show  the
			       form of the LAN specific address.

       If  cu's	 default behavior is invoked (not using the -c or -l options),
       cu will use the telno or systemname parameter to determine which medium
       to  use.	 If  a	telephone number is specified, cu will assume that you
       wish to use a telephone line and it will select an automatic call  unit
       (ACU). Otherwise, cu will assume that it is a system name. cu will fol‐
       low the uucp  calling  mechanism	 and  use  the	/etc/uucp/Systems  and
       /etc/uucp/Devices  files to obtain the best available connection. Since
       cu will choose a speed that is  appropriate  for	 the  medium  that  it
       selects,	 you may not use the -s option when this parameter is a system
       name.

       The -c and -l options modify this default behavior. -c  is  most	 often
       used   to   select   a	LAN  by	 specifying  a	Type  field  from  the
       /etc/uucp/Devices file. You must include either a telno	or  systemname
       value  when using the -c option. If the connection to systemname fails,
       a connection will be attempted using  systemname	 as  a	 LAN  specific
       address.	 The  -l  option is used to specify a device associated with a
       direct connection. If the connection is truly a	direct	connection  to
       the remote machine, then there is no need to specify a systemname. This
       is the only case where a telno or systemname parameter is  unnecessary.
       On  the	other  hand,  there may be cases in which the specified device
       connects to a dialer, so it is valid to specify a telephone number. The
       -c and -l options should not be specified on the same command line.

   Conversation Phase
       After  making  the  connection,	cu runs as two processes. The transmit
       process reads data from the standard input and, except for lines begin‐
       ning  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.

   Commands
       The transmit process interprets the following user initiated commands:

       ~.		       Terminates the conversation.

       ~!		       Escapes	to  an	interactive shell on the local
			       system.

       ~!cmd...		       Runs cmd on the local system (via sh -c).

       ~$cmd...		       Runs cmd locally and send  its  output  to  the
			       remote system.

       ~%cd		       Changes	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]	       Copies 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.

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

       ~~line		       Sends the line ~ line to the remote system.

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

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

       ~t		       Prints the values of the termio structure vari‐
			       ables  for  the	user's	terminal  (useful  for
			       debugging).

       ~l		       Prints the values of the termio structure vari‐
			       ables for the remote communication line (useful
			       for debugging).

       ~%ifc		       Toggles	between DC3/DC1 input control protocol
			       and no input control. This is useful  when  the
			       remote  system does not respond properly to the
			       DC3 and DC1 characters (can also	 be  specified
			       as ∼%nostop).

       ~%ofc		       Toggles	the output flow control setting.  When
			       enabled, outgoing data may be  flow  controlled
			       by  the	remote	host (can also be specified as
			       ∼%noostop).

       ~%divert		       Allows/disallows unsolicited diversions.	  That
			       is, diversions not specified by ~%take.

       ~%old		       Allows/disallows	 old style syntax for received
			       diversions.

       ~%nostop		       Same as	~%ifc.

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

       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, and that the remote system  must	be  using  the	Bourne
       shell,  sh.  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 follows:

       uname
       Z
       ~[X]!uname
       X
       ~~[Y]!uname
       Y

       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.

EXAMPLES
       Example 1: Dialling a system

       To dial a system whose telephone number is  9  1	 201  555  1234	 using
       1200 baud (where dialtone is expected after the	9):

       example% cu -s 1200 9=12015551234
       If the speed is not specified, "Any" is the default value.

       Example 2: Logging in to a system on a direct line

       To login to a system connected by a direct line:

       example% cu -l /dev/term/b
       or

       example% cu -l term/b

       Example 3: Dialling a system with specific line and speed

       To dial a system with a specific line and speed:

       example% cu -s 1200 -l term/b

       Example 4: Using a system name

       To use a system name:

       example% cu systemname

ENVIRONMENT VARIABLES
       See  environ(5) for descriptions of the following environment variables
       that affect the execution of cu: LC_CTYPE, LC_MESSAGES, and NLSPATH.

EXIT STATUS
       The following exit values are returned:

       0	Successful completion.

       >0	An error occurred.

FILES
       /etc/uucp/Devices       device file

       /etc/uucp/Sysfiles      system file

       /etc/uucp/Systems       system file

       /var/spool/locks/*      lock file

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       ┌─────────────────────────────┬─────────────────────────────┐
       │      ATTRIBUTE TYPE	     │	    ATTRIBUTE VALUE	   │
       ├─────────────────────────────┼─────────────────────────────┤
       │Availability		     │SUNWbnuu			   │
       └─────────────────────────────┴─────────────────────────────┘

SEE ALSO
       cat(1),	echo(1),  stty(1),  tip(1),  uname(1),	 ct(1C),   uuname(1C),
       uucp(1C), remote(4), attributes(5), environ(5)

       System Administration Guide: IP Services

NOTES
       The  cu	utility takes the default action upon receipt of signals, with
       the exception of:

       SIGHUP	       Close the connection and terminate.

       SIGINT	       Forward to the remote system.

       SIGQUIT	       Forward to the remote system.

       SIGUSR1	       Terminate the cu process without the normal  connection
		       closing sequence.

       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.  Non-
       printing	 characters  are  not  dependably transmitted using either the
       ~%put or ~%take commands. ~%put and ~%take cannot be used  over	multi‐
       ple links.  Files must be moved one link at a time.

       There  is  an artificial slowing of transmission by cu during the ~%put
       operation so that loss of data is unlikely.   Files  transferred	 using
       ~%take  or ~%put must contain a trailing newline, otherwise, the opera‐
       tion will hang.	Entering a <Control-D> command usually clears the hang
       condition.

SunOS 5.10			  11 May 2001				cu(1C)
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