cu(1)
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cu Command
call another UNIX system
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SYNTAX
cu [-sspeed] [-lline] [-h] [-t] [-d] [-o | -e] [-n] telno
cu [ -s speed ] [ -h ] [ -d ] [ -o | -e ] -l line
cu [-h] [-d] [-o | -e] systemname
DESCRIPTION
cu calls up another UNIX system, a terminal, or possibly a non-
UNIX system. It manages an interactive conversation with
possible transfers of ASCII files.
cu accepts the following options and arguments:
-sspeed Specifies 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
/usr/lib/uucp/Devices file. Most modems are either
300 or 1200 baud; however, newer models may be 2400.
Directly connected lines may be set to a speed higher
than 1200 baud.
-lline Specifies a device name to use as the communication
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 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 (e.g., /dev/ttyab) in
which case a telephone number (telno) is not
required. The specified device need not be in the
/dev directory. If the specified device is
associated with an auto dialer, a telephone number
must be provided. Use of this option with systemname
rather than telno will not give the desired result
(see systemname below).
-h Emulates local echo, supporting calls to other
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computer systems which expect terminals to be set to
half-duplex mode.
-t Used to dial an ASCII terminal which has been set to
auto answer. Appropriate mapping of carriage-return
to carriage-return-line-feed pairs is set.
-d Causes diagnostic traces to be printed.
-o Designates that odd parity is to be generated for
data sent to the remote system.
-n For added security, will prompt the user to provide
the telephone number to be dialed rather than taking
it from the command line.
-e Designates that even parity is to be generated for
data sent to the remote system.
telno When using an automatic dialer, the argument is the
telephone number with equal signs for secondary dial
tone or minus signs placed appropriately for delays
of 4 seconds.
systemname A uucp system name may be used rather than a
telephone number; in this case, cu will obtain an
appropriate direct line or telephone number from -
/usr/lib/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 the systems file
contains a login for a specific user, cu will log you
in as that user.
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 DC3/DC1 protocol (^s/^q) is used to
control input from the remote so the buffer is not overrun.
Lines beginning with ~ have special meanings as described below:
The transmit process interprets the following user initiated
commands:
~. terminate the conversation.
~! escape to an interactive shell on the local
system.
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~!cmd... run cmd on the local system (via sh -c).
~$cmd... run 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
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 transmit a BREAK to the remote system (which
can also be specified as ~%b).
~%debug toggles the -d debugging option on or off
(which can also be specified as ~%d).
~t prints the values of the termio(7) structure
variables for the user's terminal (useful for
debugging).
~l prints the values of the termio(7) structure
variables for the remote communication line
(useful for debugging).
~%nostop toggles between DC3/DC1 (^s/^q) input control
protocol and no input control. This is
useful in case the remote system is one which
does not respond properly to the DC3 and DC1
characters.
The receive process normally copies data from the remote system
to its standard output. Internally the program accomplishes this
by initiating an output redirection to a file when a line from
the remote begins with ~.
Data from the remote is redirected (or appended, if >> is used)
to file on the local system. A trailing ~> marks the end of the
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redirection.
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 these current control
characters on the local system. Backslashes are inserted at
appropriate places.
The use of ~%take requires the existence of echo(1), cat(1) and
test(1) on the remote system. ~%Take will not work if you are
logged in to a C shell on the remote system; the C shell does not
support the test command. Also, tabs mode (See stty(1)) should
be set on the remote system if tabs are to be copied without
expansion to spaces.
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 ~~. Executing a tilde command
reminds the user of the local system uname. For example, uname
can be executed on Z, X, and Y as follows:
uname
Z
~[X]!uname
X
~~[Y]!uname
Y
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.
EXAMPLES
To dial a system whose telephone number is 9 1201 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 a specific line and a specific speed:
cu -s1200 -l ttyXX
To dial a system using a specific line associated with an auto
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dialer:
cu -l culXX 9=12015551212
To use a system name:
cu systemname
FILES
/usr/lib/uucp/Systems
/usr/lib/uucp/Devices
/usr/spool/locks/LCK..(tty-device)
SEE ALSO
cat(1), ct(1), echo(1), stty(1), uucp(1), uname(1).
DIAGNOSTICS
Exit code is zero for normal exit, otherwise, one.
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.
cu between an IMBR1 and a penril modem will not return a login
prompt immediately upon connection. A carriage return will
return the prompt.
BUGS
There is an artificial slowing of transmission by cu during the
~%put operation so that loss of data is unlikely.
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