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CU(1C)                                                                  CU(1C)



NAME
       cu - connect to remote system

SYNOPSIS
       cu [ -dhnt ] [ -e | -o ] [ -l line ] [ -s speed ] phone-number

       cu [ -dh ] [ -e | -o ] [ -s speed ] -l line

       cu [ -dh ] [ -e | -o ] systemname

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

       If phone-number is specified, it is the telephone number of the  system
       to  be  dialed.  Equal signs specify a pause for a secondary dial tone,
       and minus signs specify dialing delays of 4 seconds.  If systemname  is
       specified,  it  is  the UUCP name of a the system to be dialed; in this
       case, cu will obtain an appropriate direct  line  or  telephone  number
       from /etc/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.  If neither phone-number nor  systemname  are
       specified,  the  -l  line  option  must be provided; line specifies the
       device name to use.

OPTIONS
       -d          Print diagnostic traces.

       -h          Emulate local echo, supporting calls to other computer sys-
                   tems which expect terminals to be set to half-duplex mode.

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

       -t          Perform  appropriate  mapping of RETURN to RETURN-LINE-FEED
                   pairs.  This is used to dial an ASCII  terminal  which  has
                   been set to auto answer.

       -e          Generate even parity for data sent to the remote system.

       -o          Generate odd parity for data sent to the remote system.

       -l line     Specify  a  device  name  to use as the communication line.
                   This can be used to override the search that  would  other-
                   wise  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.  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 exam-
                   ple,  /dev/ttyab)  in which case a telephone number (phone-
                   number) is not required.  The specified device need not  be
                   in  the /dev directory.  If the specified device is associ-
                   ated with an auto dialer, a telephone number must  be  pro-
                   vided.   Use  of  this  option  with systemname rather than
                   phone-number will not give the desired result (see  system-
                   name below).

       -s speed    Specify  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 Devices file.  Most modems
                   are either 300 or 1200 baud.  Directly connected lines  may
                   be set to a speed higher than 1200 baud.

USAGE
       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
       XON/XOFF protocol is used to control input from the remote so the  buf-
       fer is not overrun.

   Commands
       A  tilde  (~)  appearing  as the first character of a line is an escape
       signal which directs cu to perform some special action.   The  transmit
       recognizes the following escape sequences:

       ~.          Drop the connection and exit (you may still be logged in on
                   the remote machine).

       ~!          Escape to an interactive shell on the local machine  (exit-
                   ing the shell returns you to cu).

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

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

       ~%put from [to]
                   Copy file from (on local system) to file to on remote  sys-
                   tem.   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.

       ~~line      Send the line ~line to the remote system.

       ~%break     Send a BREAK to the remote system (which can also be speci-
                   fied as ~%b).

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

       ~t          Prints the values of the termio(4) 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    Toggle 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 or XOFF  charac-
                   ters.

       The  receive process normally copies data from the remote system to its
       standard output.  Internally the program accomplishes this by  initiat-
       ing  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(1V) and cat(1V) 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(1V) and cat(1V) on the
       remote  system.   Also,  tabs  mode (see stty(1V)) should be set on the
       remote system if TAB characters are to be copied without  expansion  to
       SPACE characters.

       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 ~~.  In general, ~ executes the command on the origi-
       nal machine, ~~ executes the command on the next machine in the chain.

EXAMPLES
       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

       or
              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
       /etc/uucp/Systems        file listing remote systems
       /etc/uucp/Devices        file listing devices to use
       /var/spool/locks/LCK ..* lock file to avoid conflicts with UUCP

SEE ALSO
       cat(1V), echo(1V), stty(1V), tip(1C), uucp(1C), termio(4)

DIAGNOSTICS
       Exit code is zero for normal exit, otherwise, 1.

WARNINGS
       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.

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



                                 26 July 1988                           CU(1C)