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CU(1)			   OpenBSD Reference Manual			 CU(1)

NAME
     cu - serial terminal emulator

SYNOPSIS
     cu [-eho] [-l line] [-s speed | -speed]

DESCRIPTION
     cu is used to connect to another system over a serial link.  In the era
     before modern networks, it was typically used to connect to a modem in
     order to dial in to a remote host.	 It is now frequently used for tasks
     such as attaching to the serial console of another machine for
     administrative or debugging purposes.

     The options are as follows:

     -e	   Use even parity.  If both -e and -o are given, then no parity is
	   used (the default).

     -h	   Echo characters locally (half-duplex mode).

     -l line
	   Specify the line to use.  Either of the forms like tty00 or
	   /dev/tty00 are permitted.

	   For reasons outlined in tty(4), cua(4) devices should be used on
	   architectures which have them.  For those which do not, tty(4)
	   devices can be used.	 Users in group ``dialer'' are permitted to
	   use cua(4) devices by default; permissions on /dev/tty00 or
	   /dev/ttya can be changed, but they will revert to their defaults
	   after an upgrade or (re)install.

     -o	   Use odd parity.  If both -e and -o are given, then no parity is
	   used (the default).

     -s speed | -speed
	   Set the speed of the connection.  The default is 9600.

     Line access is logged to /var/log/aculog.	This file does not exist by
     default and has to be created to enable logging.

     Typed characters are normally transmitted directly to the remote machine
     (which does the echoing as well).	A tilde (`~') appearing as the first
     character of a line is an escape signal; the following are recognized:

	   ~^D or ~.   Drop the connection and exit.  Only the connection is
		       dropped - the login session is not terminated.

	   ~c [name]   Change directory to name (no argument implies change to
		       home directory).

	   ~!	       Escape to a shell (exiting the shell will return to
		       cu).

	   ~>	       Copy file from local to remote.	cu prompts for the
		       name of a local file to transmit.

	   ~<	       Copy file from remote to local.	cu prompts first for
		       the name of the file to be sent, then for a command to
		       be executed on the remote machine.

	   ~p from [to]
		       Send a file to a remote UNIX host.  This command causes
		       the remote UNIX system to run the following command
		       string, sending it the `from' file:

			     stty -echo; cat > 'to'; stty echo

		       If the `to' file isn't specified, the `from' file name
		       is used.	 This command is actually a UNIX specific
		       version of the ~> command.

	   ~t from [to]
		       Take a file from a remote UNIX host.  As in the ~p
		       command, the `to' file defaults to the `from' file name
		       if it isn't specified.  The remote host executes the
		       following command string to send the file to cu:

			     cat 'from'; echo '' | tr '\012' '\01'

	   ~|	       Pipe the output from a remote command to a local UNIX
		       process.	 The command string sent to the local UNIX
		       system is processed by the shell.

	   ~$	       Pipe the output from a local UNIX process to the remote
		       host.  The command string sent to the local UNIX system
		       is processed by the shell.

	   ~C	       Fork a child process on the local system to perform
		       special protocols such as XMODEM.  The child program
		       will be run with the following arrangement of file
		       descriptors:

			     0 <-> remote tty in
			     1 <-> remote tty out
			     2 <-> local tty stderr

	   ~#	       Send a BREAK to the remote system.  For systems which
		       don't support the necessary ioctl() call, the break is
		       simulated by a sequence of line speed changes and DEL
		       characters.

	   ~s	       Set a variable (see the discussion below).

	   ~v	       List all variables and their values (if set).

	   ~^Z	       Stop cu (only available with job control).

	   ~^Y	       Stop only the ``local side'' of cu (only available with
		       job control); the ``remote side'' of cu, the side that
		       displays output from the remote host, is left running.

	   ~?	       Get a summary of the tilde escapes.

     When cu prompts for an argument, for example during setup of a file
     transfer, the line typed may be edited with the standard erase and kill
     characters.  A null line in response to a prompt, or an interrupt, will
     abort the dialogue and return the user to the remote machine.

     cu guards against multiple users connecting to a remote system by opening
     modems and terminal lines with exclusive access, and by honoring the
     locking protocol used by uucico.

     During file transfers cu provides a running count of the number of lines
     transferred.  When using the ~> and ~< commands, the ``eofread'' and
     ``eofwrite'' variables are used to recognize end-of-file when reading,
     and specify end-of-file when writing (see below).	File transfers
     normally depend on hardwareflow or tandem mode for flow control.  If the
     remote system does not support hardwareflow or tandem mode, ``echocheck''
     may be set to indicate cu should synchronize with the remote system on
     the echo of each transmitted character.

   VARIABLES
     cu maintains a set of variables which control its operation.  Some of
     these variables are read-only to normal users (root is allowed to change
     anything of interest).  Variables may be displayed and set through the
     `s' escape.  The syntax for variables is patterned after vi(1) and
     Mail(1).  Supplying ``all'' as an argument to the set command displays
     all variables readable by the user.  Alternatively, the user may request
     display of a particular variable by attaching a `?' to the end.  For
     example, ``escape?''  displays the current escape character.

     Variables are numeric, string, character, or boolean values.  Boolean
     variables are set merely by specifying their name; they may be reset by
     prepending a `!' to the name.  Other variable types are set by
     concatenating an `=' and the value.  The entire assignment must not have
     any blanks in it.	A single set command may be used to interrogate as
     well as set a number of variables.	 Certain common variables have
     abbreviations.  The following is a list of common variables, their
     abbreviations, and their default values:

     baudrate	   (num) The baud rate at which the connection was
		   established; abbreviated ba.

     beautify	   (bool) Discard unprintable characters when a session is
		   being scripted; abbreviated be.

     echocheck	   (bool) Synchronize with the remote host during file
		   transfer by waiting for the echo of the last character
		   transmitted; default is off.

     eofread	   (str) The set of characters which signify an end-of-
		   transmission during a ~< file transfer command; abbreviated
		   eofr.

     eofwrite	   (str) The string sent to indicate end-of-transmission
		   during a ~> file transfer command; abbreviated eofw.

     eol	   (str) The set of characters which indicate an end-of-line.
		   cu will recognize escape characters only after an end-of-
		   line.

     escape	   (char) The command prefix (escape) character; abbreviated
		   es; default value is `~'.

     exceptions	   (str) The set of characters which should not be discarded
		   due to the beautification switch; abbreviated ex; default
		   value is ``\t\n\f\b''.

     force	   (char) The character used to force literal data
		   transmission; abbreviated fo; default value is `^P'.

     framesize	   (num) The amount of data (in bytes) to buffer between
		   filesystem writes when receiving files; abbreviated fr.

     hardwareflow  (bool) Whether hardware flow control (CRTSCTS) is enabled
		   for the connection; abbreviated hf; default value is `off'.

     host	   (str) The name of the host to which you are connected;
		   abbreviated ho.

     linedisc	   (num) The line discipline to use; abbreviated ld.

     prompt	   (char) The character which indicates an end-of-line on the
		   remote host; abbreviated pr; default value is `\n'.	This
		   value is used to synchronize during data transfers.	The
		   count of lines transferred during a file transfer command
		   is based on receipt of this character.

     raise	   (bool) Upper case mapping mode; abbreviated ra; default
		   value is off.  When this mode is enabled, all lowercase
		   letters will be mapped to uppercase by cu for transmission
		   to the remote machine.

     raisechar	   (char) The input character used to toggle uppercase mapping
		   mode; abbreviated rc; default value is `^A'.

     record	   (str) The name of the file in which a session script is
		   recorded; abbreviated rec.

     script	   (bool) Session scripting mode; abbreviated sc; default is
		   off.	 When script is true, cu will record everything
		   transmitted by the remote machine in the script record file
		   specified in record.	 If the beautify switch is on, only
		   printable ASCII characters will be included in the script
		   file (those characters between 040 and 0177).  The variable
		   exceptions is used to indicate characters which are an
		   exception to the normal beautification rules.

     tabexpand	   (bool) Expand tabs to spaces during file transfers;
		   abbreviated tab; default value is false.  Each tab is
		   expanded to 8 spaces.

     tandem	   (bool) Use XON/XOFF flow control to throttle data from the
		   remote host; abbreviated ta.	 The default value is true.

     verbose	   (bool) Verbose mode; abbreviated verb; default is true.
		   When verbose mode is enabled, cu shows the current number
		   of lines transferred during a file transfer operations, and
		   more.

ENVIRONMENT
     HOME	 The home directory to use for the ~c command.

     SHELL	 The name of the shell to use for the ~! command; default
		 value is ``/bin/sh''.

FILES
     /var/log/aculog	     line access log
     /var/spool/lock/LCK..*  lock file to avoid conflicts with uucp

SEE ALSO
     tip(1)

HISTORY
     The cu command appeared in 4.2BSD.

BUGS
     The full set of variables is undocumented and should, probably, be pared
     down.

OpenBSD 4.9			 July 22, 2010			   OpenBSD 4.9
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