CU(1C) USER COMMANDS 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 nei-
ther 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 systems which expect terminals to be
set to half-duplex mode.
-n For added security, prompt the user to provide
the telephone 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 communica-
tion 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. 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 example, /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 provided. Use of this option with sys-
temname rather than phone-number will not give
the desired result (see systemname 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 beginning 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 proto-
col is used to control input from the remote so the buffer
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 (exiting 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 system. If to is omitted, the from argu-
ment 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 specified 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 vari-
ables 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 characters.
The receive process normally copies data from the remote
system to its standard output. Internally the program
accomplishes this by initiating 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 charac-
ters are to be copied without expansion to SPACE characters.
When cu is used on system X to connect to system Y and sub-
sequently used on system Y to connect to system Z, commands
on system Y can be executed by using ~~. In general, ~ exe-
cutes the command on the original 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 char-
acters 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.
Sun Release 4.1 Last change: 26 July 1988
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