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 cu(1)                                                                 cu(1)

 NAME    [Toc]    [Back]
      cu - call another (UNIX) system; terminal emulator

 SYNOPSIS    [Toc]    [Back]
      cu [-s speed] [-l line] [-h] [-q] [-t] [-d level] [-e|-o] [-m] [-n]

    XPG4 Syntax:
      cu [-s speed] [-l line] [-h] [-q] [-t] [-d] [-e|-o] [-m] [-n]

 DESCRIPTION    [Toc]    [Back]
      cu calls up another system, which is usually a UNIX operating system,
      but can be a terminal or a non-UNIX operating system.  cu manages all
      interaction between systems, including possible transfers of ASCII

    Options    [Toc]    [Back]
      cu recognizes the following options and command-line arguments:

           -sspeed        Specify the transmission speed (110, 150, 300,
                          600, 1200, 2400, 3600, 4800, 7200, 9600, 19200).
                          The default value is 300.

           -lline         Specify a device name to use as the communication
                          line.  This can be used to override searching 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 obtained from file
                          /etc/uucp/Devices.  When the -l and -s options are
                          used simultaneously, cu searches /etc/uucp/Devices
                          to determine whether the requested speed for the
                          requested line is available.  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 usually
                          a directly connected asynchronous line (such as
                          /dev/ttyapb).  In this case, a telephone number is
                          not required, but the string dir can be used to
                          specify that a dialer is not required.  If the
                          specified device is associated with an autodialer,
 a telephone number must be provided.

           -h             Emulate local echo, supporting calls to other
                          computer systems that expect terminals to be set
                          to half-duplex mode.

           -q             Use ENQ/ACK handshake (remote system sends ENQ, cu
                          sends ACK.)

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 cu(1)                                                                 cu(1)

           -t             Used when dialing an ASCII terminal that has been
                          set to auto-answer.  Appropriate mapping of
                          carriage-return to carriage-return-line-feed pairs
                          is set.

           -dlevel        Print diagnostic traces.  level is a number from
                          0-9, where higher levels produce more detail in
                          the diagnostic messages.

           -d             (XPG4 only.) Print diagnostic traces. The level is
                          always 9.

           -e (-o)        Generate even (odd) parity for data sent to the

           -m             Specify a direct line that has modem controls.
                          Modem controls are ignored by cu.

           -n             Cause the telephone number that cu dials to be
                          requested interactively from the user rather than
                          taking it from the command line.

           telno          When using an automatic dialer, telno is the
                          telephone number, with equal signs for secondary
                          dial tone or minus signs for delays appropriately
                          placed in the telno string.

           systemname     A UUCP system name can be used instead of a
                          telephone number (see uucp(1)); in this case, cu
                          obtains an appropriate direct line or telephone
                          number from /etc/uucp/Systems (including
                          appropriate baud rate).  cu dials each telephone
                          number or direct line for systemname in the
                          Systems file until a connection is made or all the
                          entries are tried.

           dir            Using dir ensures that cu uses the line specified
                          by the -l option.

      After making the connection, cu runs as two processes:

           +  transmit process reads data from the standard input and,
              except for lines beginning with ~, passes it to the remote

           +  receive process accepts data from the remote system and,
              except for lines beginning with ~, passes it to the standard

      Normally, an automatic DC3/DC1 protocol is used to control input from
      the remote to ensure that the buffer is not overrun.  "Prompt

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 cu(1)                                                                 cu(1)

      handshaking" can be used to control transfer of ASCII files to systems
      that have no type-ahead capability but require data to be sent only
      after a prompt is given.  This is described in detail below.  Lines
      beginning with ~ have special meanings.

    Transmit Process Commands    [Toc]    [Back]
      The transmit process interprets the following commands:

           ~., ~..        Terminate the conversation.  On hard-wired lines,
                          ~. sends several EOF characters to log out the
                          session, whereas ~.. suppresses the EOF sequence.
                          In general the remote hard-wired machine is
                          unaware of the disconnect if ~.. is used.  On
                          dial-up connections, ~. and ~.. do not differ.

           ~!             Escape to an interactive shell on the local

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

           ~&             Similar to ~! but kill the receive process,
                          restarting it upon return from the shell.  This is
                          useful for invoking sub-processes that read from
                          the communication line where the receive process
                          would otherwise compete for input.

           ~&cmd ...      Run cmd on the local system (via sh -c) and kill
                          the receive process, restarting it later.

           ~|cmd          Pipe incoming data from the remote system through
                          the standard input to cmd on the local system.  To
                          terminate, reset with either a ~& or ~| command.

           ~|             Resets the receive process following a ~|cmd

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

           ~%cd           Change the directory on the local system.  Note:
                          ~!cd causes the command to be run by a sub-shell,
                          causing a return to the current directory upon

           ~%take remote_source_file [local_destination_file]
                          Copy file remote_source_file from the remote
                          system to file local_destination_file on the local
                          system.  If local_destination_file is not
                          specified, the remote_source_file argument is used
                          in both places.

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 cu(1)                                                                 cu(1)

           ~%put local_source_file [remote_destination_file]
                          Copy file local_source_file on local system to
                          file remote_destination_file on remote system.  If
                          remote_destination_file is not specified, the
                          local_source_file argument is used in both places.

           ~~ ...         Send the line ~ ...  to the remote system.  If you
                          use cu on the remote system to access a third
                          remote system, send ~~. to cause the second remote
                          cu to exit.

           ~%break        Transmit a BREAK to the remote system.

           ~%nostop       Toggle between DC3/DC1 input control protocol and
                          no input control.  This is useful if the remote
                          system does not respond properly to the DC3 and
                          DC1 characters.

           ~%<file        Send the contents of the local file to the remote
                          system using prompt handshaking. The specified
                          file is read one line at a time, and each line is
                          sent to the remote system when the prompt sequence
                          is received.  If no prompt is received by the time
                          the prompt timeout occurs, the line is sent
                          anyway.  If the timeout is set to 0 seconds, or if
                          the first character in the prompt sequence is a
                          null character (^@), the handshake always appears
                          to be satisfied immediately, regardless of whether
                          or not the remote system generates a prompt.  This
                          capability is intended mainly to facilitate
                          transfer of ASCII files from HP-UX to an HP 3000
                          system running MPE.  This is usually accomplished
                          by running the MPE FCOPY utility and giving the
                          command from=;to=destfile;new and then running the
                          cu input diversion to send the file to FCOPY which
                          saves it in destfile.  This facility might be
                          useful with other systems also, such as an HP 1000
                          running RTE.

           ~%setpt n      Specify the number of seconds to wait for a prompt
                          before giving up.  The default is 2 seconds.
                          Specifying a timeout of 0 seconds disables
                          handshaking; that is, handshake appears to
                          complete immediately.

           ~%setps xy     Set the handshake prompt to the characters xy.
                          The default is DC1.  The prompt can be any one or
                          two characters.  To specify a control character
                          for x or y, use the Ctrl-X form where a circumflex
                          (ASCII 94) precedes the character, as in ^X.  A
                          null character can be specified with ^@.  (A null

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 cu(1)                                                                 cu(1)

                          first character in the prompt implies a "null"
                          prompt, which always appears to be satisfied.) A
                          circumflex is specified by ^^.

           ~%>[>]file     Divert output from the remote system to the
                          specified file until another ~%> command is given.
                          When an output diversion is active, typing ~%>
                          terminates it, whereas ~%> anotherfile terminates
                          it and begins a new one.  The output diversion
                          remains active through a ~& subshell, but
                          unpredictable results can occur if input/output
                          diversions are intermixed with ~%take or ~%put.
                          The ~%>> command appends to the named file.  Note
                          that these commands, which are interpreted by the
                          transmit process, are unrelated to the ~> commands
                          described below, which are interpreted by the
                          receive process.

           ~susp          Suspend the cu session.  susp is the suspend
                          character set in the terminal when cu was invoked
                          (usually ^Z - see stty(1)).  As in all other lines
                          starting with tilde, a ~susp line must be
                          terminated by pressing Return.

    Receive Process    [Toc]    [Back]
      The receive process normally copies data from the remote system to its
      standard output.  A line from the remote that begins with ~> initiates
      an output diversion to a file.  The complete sequence is:

           zero or more lines to be written to file

      Data from the remote is diverted (or appended, if >> is used) to file.
      The trailing ~> terminates 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 the current ones on the local system.
      Backslashes are inserted at appropriate places.

      The use of ~%take requires that the remote system support the echo and
      cat commands (see echo(1) and cat(1).  Also, stty tabs mode should be
      set on the remote system if tabs are being copied without expansion.
      When connecting to a machine that uses the eighth bit as a parity bit,
      stty istrip mode should be set on the local system.

      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 if ~~ is used. For example, using the keyboard on system X,
      uname can be executed on Z, X, and Y as follows where lines 1, 3, and

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 cu(1)                                                                 cu(1)

      5 are keyboard commands, and lines 2, 4, and 6 are system responses:


      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.

    Environment Variables
      LANG determines the language in which messages are displayed.

      If LANG is not specified or is set to the empty string, a default of
      "C" (see lang(5)) is used instead of LANG.  If any
      internationalization variable contains an invalid setting, cu behaves
      as if all internationalization variables are set to "C".  See

    International Code Set Support    [Toc]    [Back]
      Single- and multi-byte character code sets are supported.

 DIAGNOSTICS    [Toc]    [Back]
      Exit code is zero for normal exit; non-zero (various values)

 EXAMPLES    [Toc]    [Back]
      To dial a system whose number is 9 201 555 1212 using 1200 baud:

           cu -s1200 9=2015551212

      If the speed is not specified, 300 is the default value.

      To log in on a system connected by a direct line:

           cu -l/dev/ttyXpX dir

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

           cu -s1200 -l/dev/ttyXpX dir

      To dial a system using a specific line:

           cu -l/dev/culXpX 2015551212

      To use a system name (yyyzzz):

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 cu(1)                                                                 cu(1)

           cu yyyzzz

      To connect directly to a modem:

           cu -l/dev/culXX -m dir cu -l/dev/cu1XX -m dir

 WARNINGS    [Toc]    [Back]
      cu buffers input internally.

 AUTHOR    [Toc]    [Back]
      cu was developed by AT&T and HP.

 FILES    [Toc]    [Back]

 SEE ALSO    [Toc]    [Back]
      cat(1), ct(1), echo(1), stty(1), uname(1), uucp(1), uuname(1).

      cu: SVID2, SVID3, XPG2, XPG3, XPG4

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[ Back ]
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