telnet(1) manual page

Table of Contents

## NAME

protocol

## SYNOPSIS

## DESCRIPTION

The command is used to communicate with another host using the protocol. If is invoked without the argument, it enters command mode, indicated by its prompt In this mode, it accepts and executes the commands listed below. If it is invoked with arguments, it performs an command with those arguments. Options: Specifies an 8-bit data path. This causes an attempt to negotiate the option on both input and output. Stops any character from being recognized as an escape character. If Kerberos V5 authentication is being used, the option allows the local credentials to be forwarded to the remote system, including any credentials that have already been forwarded into the local environment. Specifies no automatic login to the remote system. Specifies an 8-bit data path on output. This causes the BINARY option to be negotiated on output. Sets the IP type-of-service (TOS) option for the telnet connection to the value which can be a numeric TOS value or, on systems that support it, a symbolic TOS name found in the /etc/iptos file. Disables the type of authentication. Attempt automatic login. Currently, this sends the user name via the variable of the option if supported by the remote system. The name used is that of the current user as returned by if it agrees with the current user ID, otherwise it is the name associated with the user ID. Disables the reading of the user's file. (See the command on this man page.) Sets the initial value of the toggle to Sets the initial escape character to If is omitted, then there will be no escape character. If Kerberos V5 authentication is being used, the option allows the local credentials to be forwarded to the remote system. If Kerberos authentication is being used, the option requests that telnet obtain tickets for the remote host in realm realm instead of the remote host's realm, as determined by When connecting to the remote system, if the remote system understands the option, then will be sent to the remote system as the value for the variable USER. This option implies the option. This option may also be used with the command. Opens for recording trace information. See the command below. Specifies a user interface similar to In this mode, the escape character is set to the tilde (~) character, unless modified by the -e option. Turns on encryption of the data stream if possible. This option is not available outside of the United States and Canada. Indicates the official name, an alias, or the Internet address of a remote host. Indicates a port number (address of an application). If a number is not specified, the default port is used. When in rlogin mode, a line of the form ~. disconnects from the remote host; ~ is the telnet escape character. Similarly, the line ~^Z suspends the telnet session. The line ~^] escapes to the normal telnet escape prompt. Once a connection has been opened, will attempt to enable the option. If this fails, then will revert to one of two input modes: either qcharacter at a timeRq or qold line by lineRq depending on what the remote system supports. When is enabled, character processing is done on the local system, under the control of the remote system. When input editing or character echoing is to be disabled, the remote system will relay that information. The remote system will also relay changes to any special characters that happen on the remote system, so that they can take effect on the local system. In qcharacter at a timeRq mode, most text typed is immediately sent to the remote host for processing. In qold line by lineRq mode, all text is echoed locally, and (normally) only completed lines are sent to the remote host. The qlocal echo characterRq (initially q^ERq) may be used to turn off and on the local echo (this would mostly be used to enter passwords without the password being echoed). If the option is enabled, or if the toggle is (the default for qold line by lineq; see below), the user's and characters are trapped locally, and sent as protocol sequences to the remote side. If has ever been enabled, then the user's and are also sent as protocol sequences, and is sent as a instead of There are options (see and below) which cause this action to flush subsequent output to the terminal (until the remote host acknowledges the sequence) and flush previous terminal input (in the case of and While connected to a remote host, command mode may be entered by typing the qescape characterRq (initially q^]Rq). When in command mode, the normal terminal editing conventions are available. The following commands are available. Only enough of each command to uniquely identify it need be typed (this is also true for arguments to the and commands). The auth command manipulates the information sent through the option. Valid arguments for the auth command are as follows: Disables the specified type of authentication. To obtain a list of available types, use the command. Enables the specified type of authentication. To obtain a list of available types, use the command. Lists the current status of the various types of authentication. Close a session and return to command mode. Displays all, or some, of the and values (see below). The encrypt command manipulates the information sent through the option. Note: Because of export controls, the option is not supported outside of the United States and Canada. Valid arguments for the encrypt command are as follows: Disables the specified type of encryption. If you omit the input and output, both input and output are disabled. To obtain a list of available types, use the command. Enables the specified type of encryption. If you omit input and output, both input and output are enabled. To obtain a list of available types, use the command. This is the same as the command. This is the same as the command. This is the same as the command. This is the same as the command. Attempts to start encryption. If you omit and both input and output are enabled. To obtain a list of available types, use the command. Lists the current status of encryption. Stops encryption. If you omit input and output, encryption is on both input and output. Sets the default type of encryption to be used with later or commands. The command is used to manipulate the the variables that my be sent through the option. The initial set of variables is taken from the users environment, with only the and variables being exported by default. The variable is also exported if the or options are used.
Valid arguments for the command are: Define the variable to have a value of Any variables defined by this command are automatically exported. The may be enclosed in single or double quotes so that tabs and spaces may be included. Remove from the list of environment variables. Mark the variable to be exported to the remote side. Mark the variable to not be exported unless explicitly asked for by the remote side. List the current set of environment variables. Those marked with a will be sent automatically, other variables will only be sent if explicitly requested. Prints out help information for the command. Sends the option to the remote side. This command is similar to a command; however, if the remote side does not support the option, nothing happens. If, however, the remote side does support the option, this command should cause the remote side to close the connection. If the remote side also supports the concept of suspending a user's session for later reattachment, the logout argument indicates that you should terminate the session immediately. is one of several options, depending on the state of the session. The remote host is asked for permission to go into the requested mode. If the remote host is capable of entering that mode, the requested mode will be entered. Disable the option, or, if the remote side does not understand the option, then enter qcharacter at a timeq mode. Enable the option, or, if the remote side does not understand the option, then attempt to enter qold-line-by-lineq mode. Attempt to enable (disable) the mode of the option. This requires that the option be enabled. Attempt to enable (disable) the mode of the option. This requires that the option be enabled. Attempt to enable (disable) the mode of the option. This requires that the option be enabled. Attempt to enable (disable) the mode of the option. This requires that the option be enabled. Prints out help information for the command. Open a connection to the named host. If no port number is specified, will attempt to contact a server at the default port. The host specification may be either a host name (see or an Internet address specified in the qdot notationRq (see The option may be used to specify the user name to be passed to the remote system via the option. When connecting to a non-standard port, omits any automatic initiation of options. When the port number is preceded by a minus sign, the initial option negotiation is done. After establishing a connection, the file in the users home directory is opened. Lines beginning with a # are comment lines. Blank lines are ignored. Lines that begin without white space are the start of a machine entry. The first thing on the line is the name of the machine that is being connected to. The rest of the line, and successive lines that begin with white space are assumed to be commands and are processed as if they had been typed in manually to the command prompt. Close any open session and exit An end of file (in command mode) will also close a session and exit. Sends one or more special character sequences to the remote host. The following are the arguments which may be specified (more than one argument may be specified at a time): Sends the (Abort processes) sequence. Sends the (Abort Output) sequence, which should cause the remote system to flush all output the remote system the user's terminal. Sends the (Are You There) sequence, to which the remote system may or may not choose to respond. Sends the (Break) sequence, which may have significance to the remote system. Sends the (Erase Character) sequence, which should cause the remote system to erase the last character entered. Sends the (Erase Line) sequence, which should cause the remote system to erase the line currently being entered. Sends the (End Of File) sequence. Sends the (End of Record) sequence. Sends the current escape character (initially q^Rq). Sends the (Go Ahead) sequence, which likely has no significance to the remote system. If the remote side supports the command, will send the subnegotiation to request that the server send its current option status. Sends the (Interrupt Process) sequence, which should cause the remote system to abort the currently running process. Sends the (No OPeration) sequence. Sends the (SUSPend process) sequence. Sends the sequence. This sequence causes the remote system to discard all previously typed (but not yet read) input. This sequence is sent as urgent data (and may not work if the remote system is a system -- if it doesn't work, a lower case qrRq may be echoed on the terminal). Sends the sequence. can be either a decimal number between 0 and 255, or a symbolic name for a specific command. can also be either or to print out help information, including a list of known symbolic names. Prints out help information for the command. The command will set any one of a number of variables to a specific value or to The special value turns off the function associated with the variable, this is equivalent to using the command. The command will disable or set to any of the specified functions. The values of variables may be interrogated with the command. The variables which may be set or unset, but not toggled, are listed here. In addition, any of the variables for the command may be explicitly set or unset using the and commands. If is in localchars mode, or is enabled, and the status character is typed, a sequence (see preceding) is sent to the remote host. The initial value for the "Are You There" character is the terminal's status character. This is the value (initially q^ERq) which, when in qline by lineRq mode, toggles between doing local echoing of entered characters (for normal processing), and suppressing echoing of entered characters (for entering, say, a password). If is operating in or qold line by lineRq mode, entering this character as the first character on a line will cause this character to be sent to the remote system. The initial value of the eof character is taken to be the terminal's character. If is in mode (see below), if is operating in qcharacter at a timeRq mode, then when this character is typed, a sequence (see above) is sent to the remote system. The initial value for the erase character is taken to be the terminal's character. This is the escape character (initially q^[Rq) which causes entry into command mode (when connected to a remote system). If is in mode (see below) and the character is typed, a sequence (see above) is sent to the remote host. The initial value for the flush character is taken to be the terminal's character. If is operating in these are the characters that, when typed, cause partial lines to be forwarded to the remote system. The initial value for the forwarding characters are taken from the terminal's eol and eol2 characters. If is in mode (see below) and the character is typed, a sequence (see above) is sent to the remote host. The initial value for the interrupt character is taken to be the terminal's character. If is in mode (see below), if is operating in qcharacter at a timeRq mode, then when this character is typed, a sequence (see above) is sent to the remote system. The initial value for the kill character is taken to be the terminal's character. If is operating in or qold line by lineq mode, then this character is taken to be the terminal's character. The initial value for the lnext character is taken to be the terminal's character. If is in mode (see below) and the character is typed, a sequence (see above) is sent to the remote host. The initial value for the quit character is taken to be the terminal's character. If is operating in or qold line by lineq mode, then this character is taken to be the terminal's character. The initial value for the reprint character is taken to be the terminal's character. This is the rlogin escape character. If set, the normal escape character is ignored unless it is preceded by this character at the beginning of a line. This character, at the beginning of a line followed by a "." closes the connection; when followed by a ^Z it suspends the telnet command. The initial state is to disable the rlogin escape character. If the option has been enabled, then this character is taken to be the terminal's character. The initial value for the kill character is taken to be the terminal's character. If the option has been enabled, then this character is taken to be the terminal's character. The initial value for the kill character is taken to be the terminal's character. If is in mode, or is enabled, and the character is typed, a sequence (see above) is sent to the remote host. The initial value for the suspend character is taken to be the terminal's character. This is the file to which the output, caused by or tracing being will be written. If it is set to then tracing information will be written to standard output (the default). If is operating in or qold line by lineq mode, then this character is taken to be the terminal's character. The initial value for the worderase character is taken to be the terminal's character. Displays the legal commands. The command (Set Local Characters) is used to set or change the state of the special characters when the option has been enabled. Special characters are characters that get mapped to commands sequences (like or or line editing characters (like and By default, the local special characters are exported. Verify the current settings for the current special characters. The remote side is requested to send all the current special character settings, and if there are any discrepancies with the local side, the local side will switch to the remote value. Switch to the local defaults for the special characters. The local default characters are those of the local terminal at the time when was started. Switch to the remote defaults for the special characters. The remote default characters are those of the remote system at the time when the connection was established. Prints out help information for the command. Show the current status of This includes the peer one is connected to, as well as the current mode. Toggle (between and various flags that control how responds to events. These flags may be set explicitly to or using the and commands listed above. More than one argument may be specified. The state of these flags may be interrogated with the command. Valid arguments are: Turns on debugging information for the authentication code. If and are both then when the or characters are recognized (and transformed into sequences; see above for details), refuses to display any data on the user's terminal until the remote system acknowledges (via a option) that it has processed those sequences. The initial value for this toggle is if the terminal user had not done an "stty noflsh", otherwise (see When the option is negotiated, by default the actual encryption (decryption) of the data stream does not start automatically. The autoencrypt (autodecrypt) command states that encryption of the output (input) stream should be enabled as soon as possible. Note: Because of export controls, the option is not supported outside the United States and Canada. If the remote side supports the option attempts to use it to perform automatic authentication. If the option is not supported, the user's login name are propagated through the option. This command is the same as specifying option on the command. If and are both then when either the or characters is typed (see above for descriptions of the and characters), the resulting sequence sent is followed by the sequence. This procedure cause the remote system to begin throwing away all previously typed input until both of the sequences have been read and acted upon. The initial value of this toggle is Enable or disable the option on both input and output. Enable or disable the option on input. Enable or disable the option on output. If this is then carriage returns will be sent as If this is then carriage returns will be send as The initial value for this toggle is Toggle carriage return mode. When this mode is enabled, most carriage return characters received from the remote host will be mapped into a carriage return followed by a line feed. This mode does not affect those characters typed by the user, only those received from the remote host. This mode is not very useful unless the remote host only sends carriage return, but never line feed. The initial value for this toggle is Toggles socket level debugging (useful only to the The initial value for this toggle is Turns on debugging information for the encryption code. If this is then the and characters (see above) are recognized locally, and transformed into (hopefully) appropriate control sequences (respectively and see above). The initial value for this toggle is in qold line by lineRq mode, and in qcharacter at a timeRq mode. When the option is enabled, the value of is ignored, and assumed to always be If has ever been enabled, then is sent as and suspend are sent as see above). Toggles the display of all network data (in hexadecimal format). The initial value for this toggle is Toggles the display of some internal protocol processing (having to do with options). The initial value for this toggle is When the toggle is enabled, if is enabled the output from the command will be formatted in a more user readable format. Spaces are put between each character in the output, and the beginning of any escape sequence is preceded by a '*' to aid in locating them. When the skiprc toggle is skips the reading of the file in the users home directory when connections are opened. The initial value for this toggle is Toggles the display of all terminal data (in hexadecimal format). The initial value for this toggle is When the toggle is prints out a message each time encryption is enabled or disabled. The initial value for this toggle is Note: Because of export controls, data encryption is not supported outside of the United States and Canada. Displays the legal commands. Suspend This command only works when the user is using the Execute a single command in a subshell on the local system. If is omitted, then an interactive subshell is invoked. Get help. With no arguments, prints a help summary. If a command is specified, will print the help information for just that command.

##

ENVIRONMENT uses at least the and environment variables. Other environment variables may be propagated to the other side via the option.

## SEE ALSO

## FILES

user customized telnet startup values

## HISTORY

The command appeared in

## NOTES

On some remote systems, echo has to be turned off manually when in qold line by lineRq mode. In qold line by lineRq mode or the terminal's character is only recognized (and sent to the remote system) when it is the first character on a line.

Table of Contents

- NAME
- SYNOPSIS
- DESCRIPTION
- ENVIRONMENT
- SEE ALSO
- FILES
- HISTORY
- NOTES