NAME

cu − call another UNIX system

SYNOPSIS

cu [ −ctype | −lline ] [ −sspeed ] [ −bn ] [ −h ] [ −n ] [ −t ] [ −d ] [ −o ] [ −e ] [ destination ]
 

AVAILABILITY

SUNWbnuu

DESCRIPTION

cu calls up another UNIX system, a terminal, or possibly a non-UNIX system.  It manages an interactive conversation with possible transfers of files.  It is convenient to think of cu as operating in two phases.  The first phase is the connection phase in which the connection is established.  cu then enters the conversation phase.  The −d option is the only one that applies to both phases. 

OPTIONS

cu accepts many options.  The −c, −l, and −s options play a part in selecting the medium; the remaining options are used in configuring the line. 

−ctype The first field in the Devices file is the "Type" field.  The −c option forces cu to only use entries in the "Type" field that match the user specified type.  The specified type is usually the name of a local area network. 

−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 /etc/uucp/Devices file.  Most modems are either 300, 1200, or 2400 baud.  Directly connected lines may be set to a speed higher than 2400 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 record in which line matches the second field (the Line field).  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.  In the general case where a specified device is a directly connected asynchronous line (for instance, /dev/term/ab), 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.  If destination is used with this option, it must be a telephone number. 

−bn Forces n to be the number of bits processed on the line.  n is either 7 or 8.  This allows connection between systems with different character sizes.  By default, the character size of the line is set to the same as the current local terminal. 

−h Set communication mode to half-duplex.  This option emulates the local echo(1) command in order to support calls to other computer systems that expect terminals to be set to half-duplex mode. 

−n Request user prompt for telephone number.  For added security, this option will prompt the user to provide the telephone number to be dialed, rather than taking it from the command line. 

−t Used to dial a terminal which has been set to auto answer.  Appropriate mapping of carriage-return to carriage-return-line-feed pairs is set. 

−d Diagnostic traces are printed. 

−o Set an ODD data parity.  This option designates that ODD parity is to be generated for data sent to the remote system. 

−e Set an EVEN data parity.  This option designates that EVEN parity is to be generated for data sent to the remote system. 

USAGE

Connection Phase

cu uses the same mechanism that uucp does to establish a connection.  This means that it will use the uucp control files /etc/uucp/Devices and /etc/uucp/Systems.  This gives cu the ability to choose from several different media to establish the connection.  The possible media include telephone lines, direct connections, and local area networks (LAN).  The Devices file contains a list of media that are available on your system.  The Systems file contains information for connecting to remote systems, but it is not generally readable. 

The destination parameter from the command line is used to tell cu what system you wish to connect to.  destination can be blank, a telephone number, a system name, or a LAN specific address.  A telephone number is a string consisting of the tone dial characters (the digits 0 through 9, ∗, and #) plus the special characters = and −.  The equal sign designates a secondary dial tone and the minus sign creates a 4 second delay.  A system name is the name of any computer that uucp can call; the uuname command prints a list of these names.  The documentation for your LAN will show the form of the LAN specific address. 

If cu’s default behavior is invoked (not using the −c or −l options), cu will use destination to determine which medium to use.  If destination is a telephone number, cu will assume that you wish to use a telephone line and it will select an automatic call unit (ACU).  If the destination is not a telephone number, then cu will assume that it is a system name.  cu will follow the uucp calling mechanism and use the Systems and Devices files to obtain the best available connection.  Since cu will choose a speed that is appropriate for the medium that it selects, you may not use the −s option when destination is a system name. 

The −c and −l options modify this default behavior.  −c is most often used to select a LAN by specifying a Type field from the Devices file.  Here, destination is assumed to be a system name.  If the connection attempt to system name fails, a connection will be attempted using destination as a LAN specific address.  The −l option is used to specify a device associated with a direct connection.  If the connection is truly a direct connection to the remote machine, then there is no need to specify a destination. This is the only case where a blank destination is allowed.  On the other hand, there may be cases in which the specified device connects to a dialer, so it is valid to specify a telephone number as a destination. The −c and −l options should not be specified on the same command line. 

Conversation Phase

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 is used to control input from the remote so the buffer is not overrun.  Lines beginning with ~ have special meanings. 

Commands

The transmit process interprets the following user initiated commands:

~. Terminate the conversation. 

~!  Escape to an interactive shell on the local system. 

~!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. 

~~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 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). 

~%ifc Toggles between DC3/DC1 input control protocol and no input control.  This is useful when the remote system does not respond properly to the DC3 and DC1 characters (can also be specified as ∼%nostop). 

~%ofc Toggles the output flow control setting.  When enabled, outgoing data may be flow controlled by the remote host (can also be specified as ∼%noostop). 

~%divert Allow/disallow unsolicited diversions.  That is, diversions not specified by ~%take. 

~%old Allow/disallow old style syntax for received diversions. 

The receive process normally copies data from the remote system to the standard output of the local system.  It may also direct the output to local files. 

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) and cat(1) on the remote system.  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 1 201 555 1234 using 1200 baud (where dialtone is expected after the 9):

example% cu −s1200 9=12015551234

If the speed is not specified, "Any" is the default value. 

To login to a system that is on a Datakit VCS local area network, but which has not been defined by your administrator (for example, is not entered in the /etc/uucp/Systems file(s)):

example% cu −c DK address

DK is the name of the Datakit local area network, and address is the Datakit address which is of the form, /area/exchange/machine. 

To login to a system connected by a direct line:

example% cu −l /dev/term/XX

or

example% cu −l term/XX

To dial a system with a specific line and speed:

example% cu −s1200 −l term/XX

To dial a system using a specific line associated with an auto dialer:

example% cu −l culXX 9=12015551234

To use a system name:

example% cu systemname

FILES

/etc/uucp/Devices

/etc/uucp/Sysfiles

/etc/uucp/Systems

/var/spool/locks/∗

SEE ALSO

cat(1), ct(1C), echo(1), stty(1), uname(1), uucp(1C)

DIAGNOSTICS

Exit code is zero for normal exit, otherwise, one. 

NOTES

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.  ~%put and ~%take cannot be used over multiple links.  Files must be moved one link at a time. 

There is an artificial slowing of transmission by cu during the ~%put operation so that loss of data is unlikely.  Files transferred using ~%take or ~%put must contain a trailing newline, otherwise, the operation will hang.  Entering a CTRL-d command usually clears the hang condition. 

SunOS 5.1/SPARC  —  Last change: 14 Sep 1992