how to use cu command

# man cu  :em11:
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cu(1)                                                                cu(1)

NAME

  cu - Connects directly or indirectly to a remote system

SYNOPSIS

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

  cu [-dhnt] [-e  | -o] system

  The cu command connects one system to a remote system.  If the remote sys-
  tem is running the proper software, cu provides additional capabilities,
  such as file transfer.

STANDARDS

  Interfaces documented on this reference page conform to industry standards
  as follows:

  cu:  XCU5.0

  Refer to the standards(5) reference page for more information about indus-
  try standards and associated tags.

OPTIONS

  -d  Prints diagnostic traces.

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

  -h  Emulates local echo, supporting calls to other systems that expect ter-
   minals to be set to half-duplex mode.

  -l line
   Specifies a device name to use as the communications line.  This can be
   used to override the search that would otherwise take place for the
   first available line with the right speed.  When the -l option is used
   without the -s option, the speed of a line is taken from the
   /usr/lib/uucp/Devices file.

   When the -l and -s options are used together, cu searches the
   /usr/lib/uucp/Devices file to check whether the requested speed is
   available for the specified line.  If so, the connection is made at the
   requested speed; otherwise, an error message is printed, and the call
   is not made.

   The specified device is generally a hardwired asynchronous line (for
   example, /dev/tty2), in which case a telephone number
   (telephone_number) is not required.  If the specified device is associ-
   ated with a modem, a telephone number must be provided.  Using this
   option with system rather than with telephone_number does not give the
   desired result (see system, which follows).

   [Tru64 UNIX]  Under ordinary circumstances, you should not have to
   specify the transmission speed, or a line/device.  The default values
   should be sufficient.  (See your system administrator for more informa-
   tion.)

  -n  Prompts you to provide the telephone number to be dialed, rather than
   taking it from the command line (for added security).

  -o  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, or 9600 baud).
   The default value is Any speed, which instructs the system to use the
   rate appropriate for the default (or specified) transmission line.
   (The order of the transmission lines is specified in the
   /usr/lib/uucp/Devices file.)  Most modems operate at 300, 1200, or 2400
   baud, while most hardwired lines are set to 1200 baud or higher.  When
   transferring data such as a file between a local and a remote system, a
   speed of 300 baud may occasionally need to be specified.  The lower
   baud rate results in less interference on the line.

  -t  Used to dial a terminal that has been set to auto-answer.  Appropriate
   mapping of carriage-return to carriage-return/linefeed pairs is set.

OPERANDS

  telephone_number
   When using a modem, the argument is the telephone number, with
   appropriately placed equal signs for secondary dial tones, or dashes
   for delays of 4 seconds.

  system
   The name of the remote system with which a connection is established.
   A system name can be used rather than a telephone number; in that case,
   cu obtains an appropriate hardwired line or telephone number from
   /usr/lib/uucp/Systems.  System names must be ASCII characters only.

   [Tru64 UNIX]  Do not use the system operand in conjunction with the -l
   and -s options.  If you do, cu connects to the first available line for
   the requested system name, ignoring the specified line and speed.

DESCRIPTION

  The cu command can establish the connection over a hardwired line, or over
  a telephone line via a modem.  Once the connection is established, you can
  be logged in on both systems at the same time, executing commands on either
  one without dropping the communications link.  If the remote computer is
  also running the proper software (see Additional Information), you can
  transfer files between the two systems.

  [Tru64 UNIX]  The system should already be configured to use the cu com-
  mand.  (See your system administrator for more information.)

  [Tru64 UNIX]  After issuing cu from the local system, you must press
  <Return>; and then log in to the remote system.

  After making the connection, cu runs as two concurrent processes:  the
  transmit process reads data from standard input and, except for lines
  beginning with a ~ (tilde), passes that data to the remote terminal.  The
  receive process accepts data from the remote system and, except for lines
  beginning with a ~ (tilde), passes it to standard output.  To control input
  from the remote system so the buffer is not overrun, cu uses an automatic
  XON/XOFF protocol.

  In addition to issuing regular system commands on the remote system, you
  can also issue special cu local commands, which are preceded by a ~
  (tilde).  Use these ~ commands to issue system commands on the local system
  and to perform tasks such as transferring files between two systems.

  Local Tilde Commands

  The transmit process interprets lines beginning with a tilde in the follow-
  ing ways:

  ~.  Logs you off the remote computer and terminates the remote connection.
   Depending on the interconnection hardware, it may be necessary to use a
   ~. to terminate the conversation even if the normal log off sequence
   was used.

  ~!  Returns you to an interactive shell on the local system.  Toggle
   between the local and remote systems using ~! (remote to local) and
   End-of-File (local to remote).

  ~!command
   Executes the command denoted by command on the local system via sh -c.

  ~$command
   Runs the command denoted by command locally and sends its output to the
   remote system for execution.

  ~%cddirectory
   Changes the directory on the local system to directory.

  ~%take from [to]
   Transfers files only.  Copies the from file on the remote system to the
   to file on the local system.  If to is omitted, the remote file is
   copied to the local system under the same file name.  As each block of
   the file is transferred, consecutive single digits are displayed on the
   terminal screen.

  ~%put from [to]
   Transfers files only.  Copies the from file on the local system to the
   to file on the remote system.  If to is omitted, the local file is
   copied to the remote system under the same file name.  As each block of
   the file is transferred, consecutive single digits are displayed on the
   terminal screen.  There is an artificial slowing of transmission by the
   cu command during ~%put operations so that loss of data is unlikely.

  ~~line
   Sends the string denoted by ~line to the remote system.

  ~%break
   Transmits a BREAK signal to the remote system. The BREAK can also be
   specified as ~%b.

  ~%debug
   [Tru64 UNIX]  Toggles the -debug option on or off; this can also be
   specified as ~%d.

  ~t  [Tru64 UNIX]  Prints the values of the TERMIO structure variables for
   your terminal.  This is useful for debugging.

  ~l  [Tru64 UNIX]  Prints the values of the TERMIO structure variables for
   the remote communications line.  This is 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 that does not respond
   properly to the <Ctrl-s>; and <Ctrl-q>; characters.

  [Tru64 UNIX]  As soon as you enter ~!,~%, ~$, ~t, or ~l, the system
  displays the name of the local computer in the a format such as the follow-
  ing:

   ~[system]!/%

  You then enter the command to be executed on the local computer.

  Asynchronous Events

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

  SIGHUP
   Closes the connection and terminates.

  SIGINT
   Forwards the signal to the remote system.

  SIGQUIT
   Forwards the signal to the remote system.

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

  Additional Information

+  The receive process normally copies data from the remote system to the
   local system's standard output.  Internally, the program accomplishes
   this by initiating an output diversion to a file when a line from the
   remote system begins with ~>;.

   Data from the remote system is diverted to file on the local system.
   The trailing ~>; marks the end of the diversion.

+  The use of ~%put requires stty and cat on the remote system.  It also
   requires that the current Erase and Kill characters on the remote sys-
   tem be identical to these current control characters on the local sys-
   tem.  Backslashes are inserted at appropriate places.

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

+  The cu command can be used to connect multiple systems, and commands
   can then be executed on any of the connected systems.  For example,
   issue cu on system X to connect to system Y, and then issue cu on sys-
   tem Y to connect to system Z.  System X is then the local computer,
   and systems Y and Z are remote computers.

   You can execute commands on system Z by logging in and issuing the
   command.  Commands can be executed on system X by prefixing the com-
   mand with a single tilde (~command), and on system Y by prefixing the
   command with two tildes (~~command).  In general, one tilde causes the
   specified command to be executed on the original local computer, and
   two tildes cause the command to be executed on the next system on
   which cu was issued.

   For example, once the multiple systems are connected, you can execute
   the uname command with the -n option (to display the node name) on Z,
   X, and Y as follows:
         $ uname -n
         Z

         $ ~!uname -n
         X

         $ ~~!uname -n
         Y

NOTES

  The cu utility is marked LEGACY in XCU Issue 5.

1.  [Tru64 UNIX]  After executing cu, you must log in to the remote system
   and press <Return>;.

2.  [Tru64 UNIX]  The cu command does not do integrity checking on data it
   transfers.

3.  [Tru64 UNIX]  Data fields with special cu characters may not be
   transmitted properly.

4.  [Tru64 UNIX]  Depending on the interconnection hardware, it may be
   necessary to use a ~. (tilde) to terminate the conversation, even if
   the normal logout sequence was used.

5.  [Tru64 UNIX]  There is an artificial slowing of transmission by cu5
   during the ~%put operation so that loss of data is unlikely.

EXIT STATUS

  The following exit values are returned:

  0 Successful completion.

  >;0  An error occurred.

EXAMPLES

1.  To connect to a remote system using a system name, enter:
         cu venus

   In this example, you are connected to the remote system venus, which
   is listed in the file /usr/lib/uucp/Systems.

2.  To dial a remote system whose telephone number is 1-201-555-1212,
   where dialing 9 is required to get an outside dial tone and the baud
   rate is 1200, enter:
         cu -s 1200 9=12015551212

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

3.  To log in to a system connected by a hardwired asynchronous line,
   enter:
         cu -l /dev/tty2

4.  To dial a remote system with a specified line and a specific speed,
   enter:
         cu -s 1200  -l tty3

5.  To dial a remote system using a specific line associated with a modem,
   enter:
         cu -l cul4  9=12015551212

6.  To open a virtual terminal on the local system after logging in to the
   remote system, enter:
         ~!open sh

7.  To display the contents of a file after logging in to the remote sys-
   tem, enter:
         ~!more /usr/msg/memos/file10

   The contents of file10 in the directory /usr/msg/memos on the local
   system are displayed.

8.  To copy a file from the local system to the remote system (after log-
   ging in to the remote system) without changing the file name, enter:
         ~%put /u/judith/file

   The file /u/judith/file is copied from the local system to the remote
   system without changing the name of the file.

9.  To copy a file from the local system to the remote system (after log-
   ging in to the remote system) and change the file name, enter:
         ~%put /u/judith/file /u/judith/tmpfile

   The file /u/judith/file is copied from the local to the remote system
   and renamed /u/judith/tmpfile.

10. To copy a file from the remote system to the local system (after log-
   ging in to the remote system) without changing the name of the file,
   enter:
         ~%take /u/jeanne/test1

   The file /u/jeanne/test1 is copied from the remote to the local sys-
   tem.

11. To copy a file from the remote system to the local system (after log-
   ging in to the remote system) and change the file name, enter:
         ~%take /u/jeanne/test1 /u/jeanne/tmptest

   The file /u/jeanne/test1 is copied from the remote to the local system
   and renamed /u/jeanne/tmptest.

ENVIRONMENT VARIABLES

  The following environment variables affect the execution of cu:

  LANG
   Provides a default value for the internationalization variables that
   are unset or null. If LANG is unset or null, the corresponding value
   from the default locale is used.  If any of the internationalization
   variables contain an invalid setting, the utility behaves as if none of
   the variables had been defined.

  LC_ALL
   If set to a non-empty string value, overrides the values of all the
   other internationalization variables.

  LC_CTYPE
   Determines the locale for the interpretation of sequences of bytes of
   text data as characters (for example, single-byte as opposed to multi-
   byte characters in arguments).

  LC_MESSAGES
   Determines the locale for the format and contents of diagnostic mes-
   sages written to standard error.

  NLSPATH
   Determines the location of message catalogues for the processing of
   LC_MESSAGES.

FILES

  /var/spool/locks/LCK..tty_number
   Prevents multiple use of device

  /usr/lib/uucp/Devices
   Information about available devices

  /usr/lib/uucp/Dialcodes
   Dialing code abbreviations

  /usr/lib/uucp/Dialers
   Initial handshaking on a link

  /usr/lib/uucp/Permissions
   Access permission codes

  /usr/lib/uucp/Systems
   Accessible remote systems

SEE ALSO

  Commands:  cat(1), ct(1), echo(1), rmail(1), stty(1), tip(1), uname(1),
  uucico(