Provided by: inetutils-telnet_1.9.4-11_amd64 bug

NAME

     telnet — user interface to the TELNET protocol

SYNOPSIS

     telnet [options ...] [host [port]]

DESCRIPTION

     The telnet command is used to communicate with another host using the TELNET protocol.  If
     telnet is invoked without the host argument, it enters command mode, indicated by its prompt
     (telnet>).  In this mode, it accepts and executes the commands listed below.  If it is
     invoked with arguments, it performs an open command with those arguments.

OPTIONS

     -4, --ipv4
             Use IPv4 to connect to hosts.

     -6, --ipv6
             Use IPv6 to connect to hosts.

     -8, --binary
             Specifies an 8-bit data path.  This causes an attempt to negotiate the TELNET BINARY
             option on both input and output.

     -L, --binary-output
             Specifies an 8-bit data path on output.  This causes the BINARY option to be
             negotiated on output.

     -e, --escape escape-char
             Sets the initial telnet escape character to escape-char. If escape-char is omitted,
             then there will be no escape character.

     -E, --no-escape
             Stops any character from being recognized as an escape character.

     -a, --login
             Attempt automatic login.  Currently, this sends the user name via the USER variable
             of the ENVIRON option if supported by the remote system.  The name used is that of
             the current user as returned by getlogin(2) if it agrees with the current user ID,
             otherwise it is the name associated with the user ID.

     -K, --no-login
             Specifies no automatic login to the remote system.

     -l, --user user
             When connecting to the remote system, if the remote system understands the ENVIRON
             option, then user will be sent to the remote system as the value for the variable
             USER.  This option implies the -a option.  This option may also be used with the
             open command.

     -n, --trace tracefile
             Opens tracefile for recording trace information.  See the set tracefile command
             below.

     -r, --rlogin
             Specifies a user interface similar to rlogin(1).  In this mode, the escape character
             is set to the tilde (~) character, unless modified by the -e option.

     -c, --no-rc
             Disables the reading of the user's .telnetrc file.  (See the toggle skiprc command
             on this man page.)

     -d, --debug
             Sets the initial value of the debug toggle to TRUE

     -x, --encrypt
             Turns on encryption of the data stream if possible.

     -X, --disable-auth atype
             Disables the atype type of authentication.

     -k, --realm realm
             If Kerberos authentication is being used, the -k option requests that telnet obtain
             tickets for the remote host in realm realm instead of the remote host's realm, as
             determined by krb_realmofhost(3).

     host    Indicates the official name, an alias, or the Internet address of a remote host.

     port    Indicates a port number (address of an application).  If a number is not specified,
             the default telnet port is used.

OPERATION

     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, telnet will attempt to enable the TELNET LINEMODE option.
     If this fails, then telnet will revert to one of two input modes: either “character at a
     time” or “old line by line” depending on what the remote system supports.

     When 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.

     In “character at a time” mode, most text typed is immediately sent to the remote host for
     processing.

     In “old line by line” mode, all text is echoed locally, and (normally) only completed lines
     are sent to the remote host.  The “local echo character” (initially “^E”) 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 LINEMODE option is enabled, or if the localchars toggle is TRUE (the default for “old
     line by line“; see below), the user's quit, intr, and flush characters are trapped locally,
     and sent as TELNET protocol sequences to the remote side.  If LINEMODE has ever been
     enabled, then the user's susp and eof are also sent as TELNET protocol sequences, and quit
     is sent as a TELNET ABORT instead of BREAK There are options (see toggle autoflush and
     toggle autosynch below) which cause this action to flush subsequent output to the terminal
     (until the remote host acknowledges the TELNET sequence) and flush previous terminal input
     (in the case of quit and intr).

     While connected to a remote host, telnet command mode may be entered by typing the telnet
     “escape character” (initially “^]”).  When in command mode, the normal terminal editing
     conventions are available.

     The following telnet commands are available.  Only enough of each command to uniquely
     identify it need be typed (this is also true for arguments to the mode, set, toggle, unset,
     slc, environ, and display commands).

     auth argument ...
                The auth command manipulates the information sent through the TELNET AUTHENTICATE
                option.  Valid arguments for the auth command are as follows:

                disable type  Disables the specified type of authentication.  To obtain a list of
                              available types, use the auth disable ? command.

                enable type   Enables the specified type of authentication.  To obtain a list of
                              available types, use the auth enable ? command.

                status        Lists the current status of the various types of authentication.

     close      Close a TELNET session and return to command mode.

     display argument ...
                Displays all, or some, of the set and toggle values (see below).

     encrypt argument ...
                The encrypt command manipulates the information sent through the TELNET ENCRYPT
                option.

                Note:  Because of export controls, the TELNET ENCRYPT option is not supported
                outside of the United States and Canada.

                Valid arguments for the encrypt command are as follows:

                disable type [input|output]
                              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 encrypt disable ? command.

                enable type [input|output]
                              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 encrypt enable ? command.

                input         This is the same as the encrypt start input command.

                -input        This is the same as the encrypt stop input command.

                output        This is the same as the encrypt start output command.

                -output       This is the same as the encrypt stop output command.

                start [input|output]
                              Attempts to start encryption.  If you omit input and output, both
                              input and output are enabled.  To obtain a list of available types,
                              use the encrypt enable ? command.

                status        Lists the current status of encryption.

                stop [input|output]
                              Stops encryption.  If you omit input and output, encryption is on
                              both input and output.

                type type     Sets the default type of encryption to be used with later encrypt
                              start or encrypt stop commands.

     environ arguments...
                The environ command is used to manipulate the the variables that my be sent
                through the TELNET ENVIRON option.  The initial set of variables is taken from
                the users environment, with only the DISPLAY and PRINTER variables being exported
                by default.  The USER variable is also exported if the -a or -l options are used.
                Valid arguments for the environ command are:

                define variable value
                            Define the variable variable to have a value of value. Any variables
                            defined by this command are automatically exported.  The value may be
                            enclosed in single or double quotes so that tabs and spaces may be
                            included.

                undefine variable
                            Remove variable from the list of environment variables.

                export variable
                            Mark the variable variable to be exported to the remote side.

                unexport variable
                            Mark the variable variable to not be exported unless explicitly asked
                            for by the remote side.

                list        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 environ command.

     logout     Sends the TELNET LOGOUT option to the remote side.  This command is similar to a
                close command; however, if the remote side does not support the LOGOUT option,
                nothing happens.  If, however, the remote side does support the LOGOUT option,
                this command should cause the remote side to close the 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.

     mode type  Type is one of several options, depending on the state of the 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.

                character     Disable the TELNET LINEMODE option, or, if the remote side does not
                              understand the LINEMODE option, then enter “character at a time“
                              mode.

                line          Enable the TELNET LINEMODE option, or, if the remote side does not
                              understand the LINEMODE option, then attempt to enter “old-line-by-
                              line“ mode.

                isig (-isig)  Attempt to enable (disable) the TRAPSIG mode of the LINEMODE
                              option.  This requires that the LINEMODE option be enabled.

                edit (-edit)  Attempt to enable (disable) the EDIT mode of the LINEMODE option.
                              This requires that the LINEMODE option be enabled.

                softtabs (-softtabs)
                              Attempt to enable (disable) the SOFT_TAB mode of the LINEMODE
                              option.  This requires that the LINEMODE option be enabled.

                litecho (-litecho)
                              Attempt to enable (disable) the LIT_ECHO mode of the LINEMODE
                              option.  This requires that the LINEMODE option be enabled.

                ?             Prints out help information for the mode command.

     open host [[-l] user][- port]
                Open a connection to the named host.  If no port number is specified, telnet will
                attempt to contact a TELNET server at the default port.  The host specification
                may be either a host name (see hosts(5)) or an Internet address specified in the
                “dot notation” (see inet(3)).  The [-l] option may be used to specify the user
                name to be passed to the remote system via the ENVIRON option.  When connecting
                to a non-standard port, telnet omits any automatic initiation of TELNET options.
                When the port number is preceded by a minus sign, the initial option negotiation
                is done.  After establishing a connection, the file .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 telnet commands and are processed as if they had been
                typed in manually to the telnet command prompt.

     quit       Close any open TELNET session and exit telnet.  An end of file (in command mode)
                will also close a session and exit.

     send 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):

                abort   Sends the TELNET ABORT (Abort processes) sequence.

                ao      Sends the TELNET AO (Abort Output) sequence, which should cause the
                        remote system to flush all output from the remote system to the user's
                        terminal.

                ayt     Sends the TELNET AYT (Are You There) sequence, to which the remote system
                        may or may not choose to respond.

                brk     Sends the TELNET BRK (Break) sequence, which may have significance to the
                        remote system.

                ec      Sends the TELNET EC (Erase Character) sequence, which should cause the
                        remote system to erase the last character entered.

                el      Sends the TELNET EL (Erase Line) sequence, which should cause the remote
                        system to erase the line currently being entered.

                eof     Sends the TELNET EOF (End Of File) sequence.

                eor     Sends the TELNET EOR (End of Record) sequence.

                escape  Sends the current telnet escape character (initially “^”).

                ga      Sends the TELNET GA (Go Ahead) sequence, which likely has no significance
                        to the remote system.

                getstatus
                        If the remote side supports the TELNET STATUS command, getstatus will
                        send the subnegotiation to request that the server send its current
                        option status.

                ip      Sends the TELNET IP (Interrupt Process) sequence, which should cause the
                        remote system to abort the currently running process.

                nop     Sends the TELNET NOP (No OPeration) sequence.

                susp    Sends the TELNET SUSP (SUSPend process) sequence.

                synch   Sends the TELNET SYNCH sequence.  This sequence causes the remote system
                        to discard all previously typed (but not yet read) input.  This sequence
                        is sent as TCP urgent data (and may not work if the remote system is a
                        4.2BSD system -- if it doesn't work, a lower case “r” may be echoed on
                        the terminal).

                do cmd

                dont cmd

                will cmd

                wont cmd
                        Sends the TELNET DO cmd sequence.  Cmd can be either a decimal number
                        between 0 and 255, or a symbolic name for a specific TELNET command.  Cmd
                        can also be either help or ? to print out help information, including a
                        list of known symbolic names.

                ?       Prints out help information for the send command.

     set argument value

     unset argument value
                The set command will set any one of a number of telnet variables to a specific
                value or to TRUE.  The special value off turns off the function associated with
                the variable, this is equivalent to using the unset command.  The unset command
                will disable or set to FALSE any of the specified functions.  The values of
                variables may be interrogated with the display command.  The variables which may
                be set or unset, but not toggled, are listed here.  In addition, any of the
                variables for the toggle command may be explicitly set or unset using the set and
                unset commands.

                ayt     If TELNET is in localchars mode, or LINEMODE is enabled, and the status
                        character is typed, a TELNET AYT sequence (see send ayt preceding) is
                        sent to the remote host.  The initial value for the "Are You There"
                        character is the terminal's status character.

                echo    This is the value (initially “^E”) which, when in “line by line” mode,
                        toggles between doing local echoing of entered characters (for normal
                        processing), and suppressing echoing of entered characters (for entering,
                        say, a password).

                eof     If telnet is operating in LINEMODE or “old line by line” 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 eof character.

                erase   If telnet is in localchars mode (see toggle localchars below), and if
                        telnet is operating in “character at a time” mode, then when this
                        character is typed, a TELNET EC sequence (see send ec above) is sent to
                        the remote system.  The initial value for the erase character is taken to
                        be the terminal's erase character.

                escape  This is the telnet escape character (initially “^[”) which causes entry
                        into telnet command mode (when connected to a remote system).

                flushoutput
                        If telnet is in localchars mode (see toggle localchars below) and the
                        flushoutput character is typed, a TELNET AO sequence (see send ao above)
                        is sent to the remote host.  The initial value for the flush character is
                        taken to be the terminal's flush character.

                forw1

                forw2   If TELNET is operating in 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.

                interrupt
                        If telnet is in localchars mode (see toggle localchars below) and the
                        interrupt character is typed, a TELNET IP sequence (see send ip above) is
                        sent to the remote host.  The initial value for the interrupt character
                        is taken to be the terminal's intr character.

                kill    If telnet is in localchars mode (see toggle localchars below), and if
                        telnet is operating in “character at a time” mode, then when this
                        character is typed, a TELNET EL sequence (see send el above) is sent to
                        the remote system.  The initial value for the kill character is taken to
                        be the terminal's kill character.

                lnext   If telnet is operating in LINEMODE or “old line by line“ mode, then this
                        character is taken to be the terminal's lnext character.  The initial
                        value for the lnext character is taken to be the terminal's lnext
                        character.

                quit    If telnet is in localchars mode (see toggle localchars below) and the
                        quit character is typed, a TELNET BRK sequence (see send brk above) is
                        sent to the remote host.  The initial value for the quit character is
                        taken to be the terminal's quit character.

                reprint
                        If telnet is operating in LINEMODE or “old line by line“ mode, then this
                        character is taken to be the terminal's reprint character.  The initial
                        value for the reprint character is taken to be the terminal's reprint
                        character.

                rlogin  This is the rlogin escape character.  If set, the normal TELNET 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.

                start   If the TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this
                        character is taken to be the terminal's start character.  The initial
                        value for the kill character is taken to be the terminal's start
                        character.

                stop    If the TELNET TOGGLE-FLOW-CONTROL option has been enabled, then this
                        character is taken to be the terminal's stop character.  The initial
                        value for the kill character is taken to be the terminal's stop
                        character.

                susp    If telnet is in localchars mode, or LINEMODE is enabled, and the suspend
                        character is typed, a TELNET SUSP sequence (see send susp above) is sent
                        to the remote host.  The initial value for the suspend character is taken
                        to be the terminal's suspend character.

                tracefile
                        This is the file to which the output, caused by netdata or option tracing
                        being TRUE, will be written.  If it is set to “-”, then tracing
                        information will be written to standard output (the default).

                worderase
                        If telnet is operating in LINEMODE or “old line by line“ mode, then this
                        character is taken to be the terminal's worderase character.  The initial
                        value for the worderase character is taken to be the terminal's worderase
                        character.

                ?       Displays the legal set (unset) commands.

     slc state  The slc command (Set Local Characters) is used to set or change the state of the
                the special characters when the TELNET LINEMODE option has been enabled.  Special
                characters are characters that get mapped to TELNET commands sequences (like ip
                or quit) or line editing characters (like erase and kill).  By default, the local
                special characters are exported.

                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.

                export      Switch to the local defaults for the special characters.  The local
                            default characters are those of the local terminal at the time when
                            telnet was started.

                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 TELNET connection was established.

                ?           Prints out help information for the slc command.

     status     Show the current status of telnet.  This includes the peer one is connected to,
                as well as the current mode.

     toggle arguments ...
                Toggle (between TRUE and FALSE) various flags that control how telnet responds to
                events.  These flags may be set explicitly to TRUE or FALSE using the set and
                unset commands listed above.  More than one argument may be specified.  The state
                of these flags may be interrogated with the display command.  Valid arguments
                are:

                authdebug     Turns on debugging information for the authentication code.

                autoflush     If autoflush and localchars are both TRUE, then when the ao, or
                              quit characters are recognized (and transformed into TELNET
                              sequences; see set above for details), telnet refuses to display
                              any data on the user's terminal until the remote system
                              acknowledges (via a TELNET TIMING MARK option) that it has
                              processed those TELNET sequences.  The initial value for this
                              toggle is TRUE if the terminal user had not done an "stty noflsh",
                              otherwise FALSE (see stty(1)).

                autodecrypt   When the 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.

                              Note:  Because of export controls, the TELNET ENCRYPT option is not
                              supported outside the United States and Canada.

                autologin     If the remote side supports the TELNET AUTHENTICATION option TELNET
                              attempts to use it to perform automatic authentication.  If the
                              AUTHENTICATION option is not supported, the user's login name are
                              propagated through the TELNET ENVIRON option.  This command is the
                              same as specifying a option on the open command.

                autosynch     If autosynch and localchars are both TRUE, then when either the
                              intr or quit characters is typed (see set above for descriptions of
                              the intr and quit characters), the resulting TELNET sequence sent
                              is followed by the TELNET SYNCH sequence.  This procedure should
                              cause the remote system to begin throwing away all previously typed
                              input until both of the TELNET sequences have been read and acted
                              upon.  The initial value of this toggle is FALSE.

                binary        Enable or disable the TELNET BINARY option on both input and
                              output.

                inbinary      Enable or disable the TELNET BINARY option on input.

                outbinary     Enable or disable the TELNET BINARY option on output.

                crlf          If this is TRUE, then carriage returns will be sent as <CR><LF>.
                              If this is FALSE, then carriage returns will be send as <CR><NUL>.
                              The initial value for this toggle is FALSE.

                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 FALSE.

                debug         Toggles socket level debugging (useful only to the super user).
                              The initial value for this toggle is FALSE.

                encdebug      Turns on debugging information for the encryption code.

                localchars    If this is TRUE, then the flush, interrupt, quit, erase, and kill
                              characters (see set above) are recognized locally, and transformed
                              into (hopefully) appropriate TELNET control sequences (respectively
                              ao, ip, brk, ec, and el; see send above).  The initial value for
                              this toggle is TRUE in “old line by line” mode, and FALSE in
                              “character at a time” mode.  When the LINEMODE option is enabled,
                              the value of localchars is ignored, and assumed to always be TRUE.
                              If LINEMODE has ever been enabled, then quit is sent as abort, and
                              eof and suspend are sent as eof and susp, see send above).

                netdata       Toggles the display of all network data (in hexadecimal format).
                              The initial value for this toggle is FALSE.

                options       Toggles the display of some internal telnet protocol processing
                              (having to do with TELNET options).  The initial value for this
                              toggle is FALSE.

                prettydump    When the netdata toggle is enabled, if prettydump is enabled the
                              output from the 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 TELNET escape sequence is preceded
                              by a '*' to aid in locating them.

                skiprc        When the skiprc toggle is TRUE, TELNET skips the reading of the
                              .telnetrc file in the users home directory when connections are
                              opened.  The initial value for this toggle is FALSE.

                termdata      Toggles the display of all terminal data (in hexadecimal format).
                              The initial value for this toggle is FALSE.

                verbose_encrypt
                              When the verbose_encrypt toggle is TRUE, TELNET prints out a
                              message each time encryption is enabled or disabled.  The initial
                              value for this toggle is FALSE. Note:  Because of export controls,
                              data encryption is not supported outside of the United States and
                              Canada.

                ?             Displays the legal toggle commands.

     z          Suspend telnet.  This command only works when the user is using the csh(1).

     ! [command]
                Execute a single command in a subshell on the local system.  If command is
                omitted, then an interactive subshell is invoked.

     ? [command]
                Get help.  With no arguments, telnet prints a help summary.  If a command is
                specified, telnet will print the help information for just that command.

ENVIRONMENT

     telnet uses at least the HOME, SHELL, DISPLAY, and TERM environment variables.  Other
     environment variables may be propagated to the other side via the TELNET ENVIRON option.

FILES

     ~/.telnetrc  user customized telnet startup values

HISTORY

     The telnet command appeared in 4.2BSD.

NOTES

     On some remote systems, echo has to be turned off manually when in “old line by line” mode.

     In “old line by line” mode or LINEMODE the terminal's eof character is only recognized (and
     sent to the remote system) when it is the first character on a line.