.TH CU 1 
.SH NAME
cu \- call Unix
.SH SYNOPSIS
.B cu
[
.B \-tn
]
telno
[
service-class
]
.SH DESCRIPTION
.I cu
places a data call to a given telephone number
and expects a computer to answer.
It manages an interactive conversation with possible
transfers of text files.
.I Telno
is the telephone number, consisting of digits with minus signs at appropriate
places to indicate delay for second or subsequent dial tones.
A telephone number may also be expressed symbolically.
The files
.RI $HOME /lib/cunumber
and
.I /usr/lib/cunumber
are searched for lines with up to four fields separated by
white space:
.IP
symbolic telephone number
.br
actual telephone number
.br
service class (see below)
.br
comment
.LP
If a
.I comment
is present, it is printed out when the connection is made.
.PP
The flag argument
.B \-n
causes
.I cu
merely to print out the the number that would be called, then exit.
.PP
The flag argument
.B \-t
causes
.I cu
to use the DC1/DC3 (^S/^Q) protocol to stop transmission from
the remote system when the local terminal buffers are almost full.
This argument should only be used if the remote system
understands that protocol.
.PP
An optional second command argument specifies a class of service.
Locally,
one may choose between the 103-type (slow speed)
or 112-type (high-speed)
datasets,
and perhaps between
the Centrex or the data Dimension networks.
.B D
or
.B D1200
(or just
.BR 1200 )
is 1200 baud on the Dimension system
(the default);
.B D300
is 300 baud Dimension.
Systems with their own diallers
may allow
.B C1200
and
.B C300
as well,
for 1200 and 300 baud Centrex calls.
.PP
An explicit service class on the command line overrides
any specified in a
.I cunumber
file.
.PP
After making the connection,
.I cu
runs as two processes:
the
.I send
process reads the standard input and
passes most of it to the remote system;
the
.I receive
process reads from the remote system and passes
most data to the standard output.
Lines beginning with `~' have special meanings.
.PP
The
.I send
process interprets the following:
.TP 18
~\|\fB.\|
terminate the conversation.
.br
.ns
.TP 18
~EOT
terminate the conversation
.TP 18
~<file
send the contents of
.I file
to the remote system,
as though typed at the terminal.
.TP 18
~!
invoke an interactive shell on the local system.
.TP 18
~!cmd ...
run the command on the local system
(via
.BR "sh \-c" ")."
.TP 18
~$cmd ...
run the command locally and send its output
to the remote system.
.TP 18
~b
.PD 0
.TP 18
~%break
.PD
are identical, and cause a break (300 ms. space) to be sent.
.TP 18
~%take from [to]
copy file `from' (on the remote system)
to file `to' on the local system.
If `to' is omitted,
the `from' name is used both places.
.TP 18
~%put from [to]
copy file `from' (on local system)
to file `to' on remote system.
If `to' is omitted, the `from' name is used both places.
.TP 18
~~\fB\|.\|.\|.\fR
send
the line `~\|.\|.\|.'.
.PP
The
.I receive
process handles output diversions of the following form:
.PP
\&~>[>][:]file
.br
zero or more lines to be written to file
.br
\&~>
.PP
Output is diverted (or appended, if `>>' used) to the file.
If `:' is used,
the diversion is
.I silent,
i.e., it is written only to the file.
If `:' is omitted,
output is written both to the file and to the standard output.
The trailing `~>' terminates the diversion.
.PP
The
.I receive
process also recognizes lines of the form
.PP
\&~!command
.br
or
.br
\&~:!command
.PP
which
cause
.I command
to be executed locally.
If the `:' is present the line is not printed before execution.
.PP
The use of
.B  ~%put
requires
.I stty
and
.I cat
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.
.PP
The use of
.B  ~%take
requires the existence of
.I echo
and
.I tee
on the remote system.
Also,
.B "stty tabs"
mode is required on the remote system if
tabs are to be copied without expansion.
.SH FILES
/usr/lib/cunumber,
$HOME/lib/cunumber
.SH "SEE ALSO"
dn(4), ttyld(4), dialout(3)
.SH DIAGNOSTICS
Exit code is
zero for normal exit,
nonzero (various values) otherwise.
.SH BUGS
The syntax is unique.
The speed option (\-s) should be put
back
(it is at least partially independent
of the class of service).
.PP
.B ~!
is a friend to the malicious.