.\" Copyright (c) 1983, 1990, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)telnet.1 8.6 (Berkeley) 6/1/94 .\" $FreeBSD: src/crypto/telnet/telnet/telnet.1,v 1.4.2.9 2002/04/13 10:59:08 markm Exp $ .\" .Dd January 27, 2000 .Dt TELNET 1 .Os .Sh NAME .Nm telnet .Nd user interface to the .Tn TELNET protocol .Sh SYNOPSIS .Nm .Op Fl 468EFKLNacdfruxy .Op Fl S Ar tos .Op Fl X Ar authtype .Op Fl e Ar escapechar .Op Fl k Ar realm .Op Fl l Ar user .Op Fl n Ar tracefile .Op Fl s Ar src_addr .Oo .Ar host .Op Ar port .Oc .Sh DESCRIPTION The .Nm command is used to communicate with another host using the .Tn TELNET protocol. If .Nm is invoked without the .Ar host argument, it enters command mode, indicated by its prompt .Pq Dq Li telnet\&> . In this mode, it accepts and executes the commands listed below. If it is invoked with arguments, it performs an .Ic open command with those arguments. .Pp Options: .Bl -tag -width indent .It Fl 4 Forces .Nm to use IPv4 addresses only. .It Fl 6 Forces .Nm to use IPv6 addresses only. .It Fl 8 Specifies an 8-bit data path. This causes an attempt to negotiate the .Dv TELNET BINARY option on both input and output. .It Fl E Stops any character from being recognized as an escape character. .It Fl F If Kerberos V5 authentication is being used, the .Fl F option allows the local credentials to be forwarded to the remote system, including any credentials that have already been forwarded into the local environment. .It Fl K Specifies no automatic login to the remote system. .It Fl L Specifies an 8-bit data path on output. This causes the .Dv BINARY option to be negotiated on output. .It Fl N Prevents IP address to name lookup when destination host is given as an IP address. .It Fl S Ar tos Sets the IP type-of-service (TOS) option for the telnet connection to the value .Ar tos , which can be a numeric TOS value or, on systems that support it, a symbolic TOS name found in the .Pa /etc/iptos file. .It Fl X Ar atype Disables the .Ar atype type of authentication. .It Fl a Attempt automatic login. This is now the default, so this option is ignored. Currently, this sends the user name via the .Ev USER variable of the .Ev ENVIRON option if supported by the remote system. The name used is that of the current user as returned by .Xr getlogin 2 if it agrees with the current user ID, otherwise it is the name associated with the user ID. .It Fl c Disables the reading of the user's .Pa \&.telnetrc file. (See the .Ic toggle skiprc command on this man page.) .It Fl d Sets the initial value of the .Ic debug toggle to .Dv TRUE . .It Fl e Ar escapechar Sets the initial .Nm escape character to .Ar escapechar . If .Ar escapechar is omitted, then there will be no escape character. .It Fl f If Kerberos V5 authentication is being used, the .Fl f option allows the local credentials to be forwarded to the remote system. .It Fl k Ar realm If Kerberos authentication is being used, the .Fl k option requests that .Nm obtain tickets for the remote host in realm .Ar realm instead of the remote host's realm, as determined by .Xr krb_realmofhost 3 . .It Fl l Ar user When connecting to the remote system, if the remote system understands the .Ev ENVIRON option, then .Ar user will be sent to the remote system as the value for the variable .Ev USER . This option implies the .Fl a option. This option may also be used with the .Ic open command. .It Fl n Ar tracefile Opens .Ar tracefile for recording trace information. See the .Ic set tracefile command below. .It Fl r Specifies a user interface similar to .Xr rlogin 1 . In this mode, the escape character is set to the tilde (~) character, unless modified by the .Fl e option. .It Fl s Ar src_addr Set the source IP address for the .Nm connection to .Ar src_addr , which can be an IP address or a host name. .It Fl u Forces .Nm to use .Dv AF_UNIX addresses only (e.g., .Ux domain sockets, accessed with a file path). .It Fl x Turns on encryption of the data stream if possible. This is now the default, so this option is ignored. .It Fl y Suppresses encryption of the data stream. .It Ar host Indicates the official name, an alias, or the Internet address of a remote host. If .Ar host starts with a .Ql / , .Nm establishes a connection to the corresponding named socket. .It Ar port Indicates a port number (address of an application). If a number is not specified, the default .Nm port is used. .El .Pp When in rlogin mode, a line of the form ~. disconnects from the remote host; ~ is the .Nm escape character. Similarly, the line ~^Z suspends the .Nm session. The line ~^] escapes to the normal .Nm escape prompt. .Pp Once a connection has been opened, .Nm will attempt to enable the .Dv TELNET LINEMODE option. If this fails, then .Nm will revert to one of two input modes: either \*(Lqcharacter at a time\*(Rq or \*(Lqold line by line\*(Rq depending on what the remote system supports. .Pp When .Dv LINEMODE 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. .Pp In \*(Lqcharacter at a time\*(Rq mode, most text typed is immediately sent to the remote host for processing. .Pp In \*(Lqold line by line\*(Rq mode, all text is echoed locally, and (normally) only completed lines are sent to the remote host. The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used to turn off and on the local echo (this would mostly be used to enter passwords without the password being echoed). .Pp If the .Dv LINEMODE option is enabled, or if the .Ic localchars toggle is .Dv TRUE (the default for \*(Lqold line by line\*(Rq; see below), the user's .Ic quit , .Ic intr , and .Ic flush characters are trapped locally, and sent as .Tn TELNET protocol sequences to the remote side. If .Dv LINEMODE has ever been enabled, then the user's .Ic susp and .Ic eof are also sent as .Tn TELNET protocol sequences, and .Ic quit is sent as a .Dv TELNET ABORT instead of .Dv BREAK . There are options (see .Ic toggle .Ic autoflush and .Ic toggle .Ic autosynch below) which cause this action to flush subsequent output to the terminal (until the remote host acknowledges the .Tn TELNET sequence) and flush previous terminal input (in the case of .Ic quit and .Ic intr ) . .Pp While connected to a remote host, .Nm command mode may be entered by typing the .Nm \*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). When in command mode, the normal terminal editing conventions are available. .Pp The following .Nm commands are available. Only enough of each command to uniquely identify it need be typed (this is also true for arguments to the .Ic mode , .Ic set , .Ic toggle , .Ic unset , .Ic slc , .Ic environ , and .Ic display commands). .Pp .Bl -tag -width "mode type" .It Ic auth Ar argument ... The auth command manipulates the information sent through the .Dv TELNET AUTHENTICATE option. Valid arguments for the .Ic auth command are: .Bl -tag -width "disable type" .It Ic disable Ar type Disables the specified type of authentication. To obtain a list of available types, use the .Ic auth disable ?\& command. .It Ic enable Ar type Enables the specified type of authentication. To obtain a list of available types, use the .Ic auth enable ?\& command. .It Ic status Lists the current status of the various types of authentication. .El .It Ic close Close a .Tn TELNET session and return to command mode. .It Ic display Ar argument ... Displays all, or some, of the .Ic set and .Ic toggle values (see below). .It Ic encrypt Ar argument ... The encrypt command manipulates the information sent through the .Dv TELNET ENCRYPT option. .Pp Valid arguments for the .Ic encrypt command are: .Bl -tag -width Ar .It Ic disable Ar type Xo .Op Cm input | output .Xc 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 .Ic encrypt disable ?\& command. .It Ic enable Ar type Xo .Op Cm input | output .Xc 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 .Ic encrypt enable ?\& command. .It Ic input This is the same as the .Ic encrypt start input command. .It Ic -input This is the same as the .Ic encrypt stop input command. .It Ic output This is the same as the .Ic encrypt start output command. .It Ic -output This is the same as the .Ic encrypt stop output command. .It Ic start Op Cm input | output Attempts to start encryption. If you omit .Ic input and .Ic output , both input and output are enabled. To obtain a list of available types, use the .Ic encrypt enable ?\& command. .It Ic status Lists the current status of encryption. .It Ic stop Op Cm input | output Stops encryption. If you omit input and output, encryption is on both input and output. .It Ic type Ar type Sets the default type of encryption to be used with later .Ic encrypt start or .Ic encrypt stop commands. .El .It Ic environ Ar arguments ... The .Ic environ command is used to manipulate the variables that may be sent through the .Dv TELNET ENVIRON option. The initial set of variables is populated with the contents of the following environment variables, if present: .Ev USER , PRINTER , DISPLAY , TERM , COLUMNS , LINES. Only the first three are exported, by default. .Pp Valid arguments for the .Ic environ command are: .Bl -tag -width Fl .It Ic define Ar variable [value] Define the variable .Ar variable to have a value of .Ar value . If value is empty, the value is taken from the environment variable. Any variables defined by this command are automatically exported. The .Ar value may be enclosed in single or double quotes so that tabs and spaces may be included. .It Ic undefine Ar variable Remove .Ar variable from the list of environment variables. .It Ic export Ar variable Mark the variable .Ar variable to be exported to the remote side. .It Ic unexport Ar variable Mark the variable .Ar variable to not be exported unless explicitly asked for by the remote side. .It Ic list List the current set of environment variables. Those marked with a .Cm * will be sent automatically, other variables will only be sent if explicitly requested. .It Ic ?\& Prints out help information for the .Ic environ command. .El .It Ic logout Sends the .Dv TELNET LOGOUT option to the remote side. This command is similar to a .Ic close command; however, if the remote side does not support the .Dv LOGOUT option, nothing happens. If, however, the remote side does support the .Dv LOGOUT option, this command should cause the remote side to close the .Tn TELNET 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. .It Ic mode Ar type .Ar Type is one of several options, depending on the state of the .Tn TELNET 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. .Bl -tag -width Ar .It Ic character Disable the .Dv TELNET LINEMODE option, or, if the remote side does not understand the .Dv LINEMODE option, then enter \*(Lqcharacter at a time\*(Rq mode. .It Ic line Enable the .Dv TELNET LINEMODE option, or, if the remote side does not understand the .Dv LINEMODE option, then attempt to enter \*(Lqold-line-by-line\*(Rq mode. .It Ic isig Pq Ic \-isig Attempt to enable (disable) the .Dv TRAPSIG mode of the .Dv LINEMODE option. This requires that the .Dv LINEMODE option be enabled. .It Ic edit Pq Ic \-edit Attempt to enable (disable) the .Dv EDIT mode of the .Dv LINEMODE option. This requires that the .Dv LINEMODE option be enabled. .It Ic softtabs Pq Ic \-softtabs Attempt to enable (disable) the .Dv SOFT_TAB mode of the .Dv LINEMODE option. This requires that the .Dv LINEMODE option be enabled. .It Ic litecho Pq Ic \-litecho Attempt to enable (disable) the .Dv LIT_ECHO mode of the .Dv LINEMODE option. This requires that the .Dv LINEMODE option be enabled. .It Ic ?\& Prints out help information for the .Ic mode command. .El .It Xo .Ic open Ar host .Op Fl l Ar user .Op Oo Fl Oc Ns Ar port .Xc Open a connection to the named host. If no port number is specified, .Nm will attempt to contact a .Tn TELNET server at the default port. The host specification may be either a host name (see .Xr hosts 5 ) , an Internet address specified in the \*(Lqdot notation\*(Rq (see .Xr inet 3 ) , or IPv6 host name or IPv6 coloned-hexadecimal addreess. The .Fl l option may be used to specify the user name to be passed to the remote system via the .Ev ENVIRON option. When connecting to a non-standard port, .Nm omits any automatic initiation of .Tn TELNET options. When the port number is preceded by a minus sign, the initial option negotiation is done. After establishing a connection, the file .Pa \&.telnetrc 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 .Nm commands and are processed as if they had been typed in manually to the .Nm command prompt. .It Ic quit Close any open .Tn TELNET session and exit .Nm . An end of file (in command mode) will also close a session and exit. .It Ic send Ar arguments 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): .Pp .Bl -tag -width escape .It Ic abort Sends the .Dv TELNET ABORT (Abort processes) sequence. .It Ic ao Sends the .Dv TELNET AO (Abort Output) sequence, which should cause the remote system to flush all output .Em from the remote system .Em to the user's terminal. .It Ic ayt Sends the .Dv TELNET AYT (Are You There) sequence, to which the remote system may or may not choose to respond. .It Ic brk Sends the .Dv TELNET BRK (Break) sequence, which may have significance to the remote system. .It Ic ec Sends the .Dv TELNET EC (Erase Character) sequence, which should cause the remote system to erase the last character entered. .It Ic el Sends the .Dv TELNET EL (Erase Line) sequence, which should cause the remote system to erase the line currently being entered. .It Ic eof Sends the .Dv TELNET EOF (End Of File) sequence. .It Ic eor Sends the .Dv TELNET EOR (End of Record) sequence. .It Ic escape Sends the current .Nm escape character (initially \*(Lq^\*(Rq). .It Ic ga Sends the .Dv TELNET GA (Go Ahead) sequence, which likely has no significance to the remote system. .It Ic getstatus If the remote side supports the .Dv TELNET STATUS command, .Ic getstatus will send the subnegotiation to request that the server send its current option status. .It Ic ip Sends the .Dv TELNET IP (Interrupt Process) sequence, which should cause the remote system to abort the currently running process. .It Ic nop Sends the .Dv TELNET NOP (No OPeration) sequence. .It Ic susp Sends the .Dv TELNET SUSP (SUSPend process) sequence. .It Ic synch Sends the .Dv TELNET SYNCH sequence. This sequence causes the remote system to discard all previously typed (but not yet read) input. This sequence is sent as .Tn TCP urgent data (and may not work if the remote system is a .Bx 4.2 system -- if it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). .It Ic do Ar cmd .It Ic dont Ar cmd .It Ic will Ar cmd .It Ic wont Ar cmd Sends the .Dv TELNET DO .Ar cmd sequence. .Ar Cmd can be either a decimal number between 0 and 255, or a symbolic name for a specific .Dv TELNET command. .Ar Cmd can also be either .Ic help or .Ic ?\& to print out help information, including a list of known symbolic names. .It Ic ?\& Prints out help information for the .Ic send command. .El .It Ic set Ar argument value .It Ic unset Ar argument value The .Ic set command will set any one of a number of .Nm variables to a specific value or to .Dv TRUE . The special value .Ic off turns off the function associated with the variable, this is equivalent to using the .Ic unset command. The .Ic unset command will disable or set to .Dv FALSE any of the specified functions. The values of variables may be interrogated with the .Ic display command. The variables which may be set or unset, but not toggled, are listed here. In addition, any of the variables for the .Ic toggle command may be explicitly set or unset using the .Ic set and .Ic unset commands. .Bl -tag -width escape .It Ic ayt If .Tn TELNET is in localchars mode, or .Dv LINEMODE is enabled, and the status character is typed, a .Dv TELNET AYT sequence (see .Ic send ayt preceding) is sent to the remote host. The initial value for the \*(LqAre You There\*(Rq character is the terminal's status character. .It Ic echo This is the value (initially \*(Lq^E\*(Rq) which, when in \*(Lqline by line\*(Rq mode, toggles between doing local echoing of entered characters (for normal processing), and suppressing echoing of entered characters (for entering, say, a password). .It Ic eof If .Nm is operating in .Dv LINEMODE or \*(Lqold line by line\*(Rq 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 .Ic eof character. .It Ic erase If .Nm is in .Ic localchars mode (see .Ic toggle .Ic localchars below), .Sy and if .Nm is operating in \*(Lqcharacter at a time\*(Rq mode, then when this character is typed, a .Dv TELNET EC sequence (see .Ic send .Ic ec above) is sent to the remote system. The initial value for the erase character is taken to be the terminal's .Ic erase character. .It Ic escape This is the .Nm escape character (initially \*(Lq^[\*(Rq) which causes entry into .Nm command mode (when connected to a remote system). .It Ic flushoutput If .Nm is in .Ic localchars mode (see .Ic toggle .Ic localchars below) and the .Ic flushoutput character is typed, a .Dv TELNET AO sequence (see .Ic send .Ic ao above) is sent to the remote host. The initial value for the flush character is taken to be the terminal's .Ic flush character. .It Ic forw1 .It Ic forw2 If .Nm is operating in .Dv LINEMODE , 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. .It Ic interrupt If .Nm is in .Ic localchars mode (see .Ic toggle .Ic localchars below) and the .Ic interrupt character is typed, a .Dv TELNET IP sequence (see .Ic send .Ic ip above) is sent to the remote host. The initial value for the interrupt character is taken to be the terminal's .Ic intr character. .It Ic kill If .Nm is in .Ic localchars mode (see .Ic toggle .Ic localchars below), .Ic and if .Nm is operating in \*(Lqcharacter at a time\*(Rq mode, then when this character is typed, a .Dv TELNET EL sequence (see .Ic send .Ic el above) is sent to the remote system. The initial value for the kill character is taken to be the terminal's .Ic kill character. .It Ic lnext If .Nm is operating in .Dv LINEMODE or \*(Lqold line by line\*(Rq mode, then this character is taken to be the terminal's .Ic lnext character. The initial value for the lnext character is taken to be the terminal's .Ic lnext character. .It Ic quit If .Nm is in .Ic localchars mode (see .Ic toggle .Ic localchars below) and the .Ic quit character is typed, a .Dv TELNET BRK sequence (see .Ic send .Ic brk above) is sent to the remote host. The initial value for the quit character is taken to be the terminal's .Ic quit character. .It Ic reprint If .Nm is operating in .Dv LINEMODE or \*(Lqold line by line\*(Rq mode, then this character is taken to be the terminal's .Ic reprint character. The initial value for the reprint character is taken to be the terminal's .Ic reprint character. .It Ic rlogin This is the rlogin escape character. If set, the normal .Nm 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 .Nm command. The initial state is to disable the .Nm rlogin escape character. .It Ic start If the .Dv TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this character is taken to be the terminal's .Ic start character. The initial value for the start character is taken to be the terminal's .Ic start character. .It Ic stop If the .Dv TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this character is taken to be the terminal's .Ic stop character. The initial value for the stop character is taken to be the terminal's .Ic stop character. .It Ic susp If .Nm is in .Ic localchars mode, or .Dv LINEMODE is enabled, and the .Ic suspend character is typed, a .Dv TELNET SUSP sequence (see .Ic send .Ic susp above) is sent to the remote host. The initial value for the suspend character is taken to be the terminal's .Ic suspend character. .It Ic tracefile This is the file to which the output, caused by .Ic netdata or .Ic option tracing being .Dv TRUE , will be written. If it is set to .Dq Fl , then tracing information will be written to standard output (the default). .It Ic worderase If .Nm is operating in .Dv LINEMODE or \*(Lqold line by line\*(Rq mode, then this character is taken to be the terminal's .Ic worderase character. The initial value for the worderase character is taken to be the terminal's .Ic worderase character. .It Ic ?\& Displays the legal .Ic set .Pq Ic unset commands. .El .It Ic opie Ar sequence challenge The .Ic opie command computes a response to the OPIE challenge. .It Ic slc Ar state The .Ic slc command (Set Local Characters) is used to set or change the state of the special characters when the .Dv TELNET LINEMODE option has been enabled. Special characters are characters that get mapped to .Tn TELNET commands sequences (like .Ic ip or .Ic quit ) or line editing characters (like .Ic erase and .Ic kill ) . By default, the local special characters are exported. .Bl -tag -width Fl .It Ic check 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. .It Ic export Switch to the local defaults for the special characters. The local default characters are those of the local terminal at the time when .Nm was started. .It Ic import Switch to the remote defaults for the special characters. The remote default characters are those of the remote system at the time when the .Tn TELNET connection was established. .It Ic ?\& Prints out help information for the .Ic slc command. .El .It Ic status Show the current status of .Nm . This includes the peer one is connected to, as well as the current mode. .It Ic toggle Ar arguments ... Toggle (between .Dv TRUE and .Dv FALSE ) various flags that control how .Nm responds to events. These flags may be set explicitly to .Dv TRUE or .Dv FALSE using the .Ic set and .Ic unset commands listed above. More than one argument may be specified. The state of these flags may be interrogated with the .Ic display command. Valid arguments are: .Bl -tag -width Ar .It Ic authdebug Turns on debugging information for the authentication code. .It Ic autoflush If .Ic autoflush and .Ic localchars are both .Dv TRUE , then when the .Ic ao , or .Ic quit characters are recognized (and transformed into .Tn TELNET sequences; see .Ic set above for details), .Nm refuses to display any data on the user's terminal until the remote system acknowledges (via a .Dv TELNET TIMING MARK option) that it has processed those .Tn TELNET sequences. The initial value for this toggle is .Dv TRUE if the terminal user had not done an "stty noflsh", otherwise .Dv FALSE (see .Xr stty 1 ) . .It Ic autodecrypt When the .Dv TELNET ENCRYPT 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. .It Ic autologin If the remote side supports the .Dv TELNET AUTHENTICATION option .Nm attempts to use it to perform automatic authentication. If the .Dv AUTHENTICATION option is not supported, the user's login name are propagated through the .Dv TELNET ENVIRON option. This command is the same as specifying .Fl a option on the .Ic open command. .It Ic autosynch If .Ic autosynch and .Ic localchars are both .Dv TRUE , then when either the .Ic intr or .Ic quit characters is typed (see .Ic set above for descriptions of the .Ic intr and .Ic quit characters), the resulting .Tn TELNET sequence sent is followed by the .Dv TELNET SYNCH sequence. This procedure .Ic should cause the remote system to begin throwing away all previously typed input until both of the .Tn TELNET sequences have been read and acted upon. The initial value of this toggle is .Dv FALSE . .It Ic binary Enable or disable the .Dv TELNET BINARY option on both input and output. .It Ic inbinary Enable or disable the .Dv TELNET BINARY option on input. .It Ic outbinary Enable or disable the .Dv TELNET BINARY option on output. .It Ic crlf If this is .Dv TRUE , then carriage returns will be sent as .Li <CR><LF> . If this is .Dv FALSE , then carriage returns will be send as .Li <CR><NUL> . The initial value for this toggle is .Dv FALSE . .It Ic crmod 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 .Dv FALSE . .It Ic debug Toggles socket level debugging (useful only to the .Ic super user ) . The initial value for this toggle is .Dv FALSE . .It Ic encdebug Turns on debugging information for the encryption code. .It Ic localchars If this is .Dv TRUE , then the .Ic flush , .Ic interrupt , .Ic quit , .Ic erase , and .Ic kill characters (see .Ic set above) are recognized locally, and transformed into (hopefully) appropriate .Tn TELNET control sequences (respectively .Ic ao , .Ic ip , .Ic brk , .Ic ec , and .Ic el ; see .Ic send above). The initial value for this toggle is .Dv TRUE in \*(Lqold line by line\*(Rq mode, and .Dv FALSE in \*(Lqcharacter at a time\*(Rq mode. When the .Dv LINEMODE option is enabled, the value of .Ic localchars is ignored, and assumed to always be .Dv TRUE . If .Dv LINEMODE has ever been enabled, then .Ic quit is sent as .Ic abort , and .Ic eof and .Ic suspend are sent as .Ic eof and .Ic susp (see .Ic send above). .It Ic netdata Toggles the display of all network data (in hexadecimal format). The initial value for this toggle is .Dv FALSE . .It Ic options Toggles the display of some internal .Nm protocol processing (having to do with .Tn TELNET options). The initial value for this toggle is .Dv FALSE . .It Ic prettydump When the .Ic netdata toggle is enabled, if .Ic prettydump is enabled the output from the .Ic netdata command will be formatted in a more user readable format. Spaces are put between each character in the output, and the beginning of any .Nm escape sequence is preceded by a '*' to aid in locating them. .It Ic skiprc When the skiprc toggle is .Dv TRUE , .Nm skips the reading of the .Pa \&.telnetrc file in the users home directory when connections are opened. The initial value for this toggle is .Dv FALSE . .It Ic termdata Toggles the display of all terminal data (in hexadecimal format). The initial value for this toggle is .Dv FALSE . .It Ic verbose_encrypt When the .Ic verbose_encrypt toggle is .Dv TRUE , .Nm prints out a message each time encryption is enabled or disabled. The initial value for this toggle is .Dv FALSE . .It Ic ?\& Displays the legal .Ic toggle commands. .El .It Ic z Suspend .Nm . This command only works when the user is using the .Xr csh 1 . .It Ic \&! Op Ar command Execute a single command in a subshell on the local system. If .Ar command is omitted, then an interactive subshell is invoked. .It Ic ?\& Op Ar command Get help. With no arguments, .Nm prints a help summary. If .Ar command is specified, .Nm will print the help information for just that command. .El .Sh ENVIRONMENT .Nm uses at least the .Ev HOME , .Ev SHELL , .Ev DISPLAY , and .Ev TERM environment variables. Other environment variables may be propagated to the other side via the .Dv TELNET ENVIRON option. .Sh SEE ALSO .Xr rlogin 1 , .Xr rsh 1 , .Xr hosts 5 , .Xr nologin 5 , .Xr telnetd 8 .Sh FILES .Bl -tag -width ~/.telnetrc -compact .It Pa ~/.telnetrc user customized telnet startup values .El .Sh HISTORY The .Nm command appeared in .Bx 4.2 . .Pp IPv6 support was added by WIDE/KAME project. .Sh NOTES On some remote systems, echo has to be turned off manually when in \*(Lqold line by line\*(Rq mode. .Pp In \*(Lqold line by line\*(Rq mode or .Dv LINEMODE the terminal's .Ic eof character is only recognized (and sent to the remote system) when it is the first character on a line.