1.\" Copyright (c) 1983, 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)telnet.1 8.6 (Berkeley) 6/1/94 29.\" $FreeBSD$ 30.\" 31.Dd August 7, 2020 32.Dt TELNET 1 33.Os 34.Sh NAME 35.Nm telnet 36.Nd user interface to the 37.Tn TELNET 38protocol 39.Sh SYNOPSIS 40.Nm 41.Op Fl 468EFKLNacdfruxy 42.Op Fl B Ar baudrate 43.Op Fl S Ar tos 44.Op Fl X Ar authtype 45.Op Fl e Ar escapechar 46.Op Fl k Ar realm 47.Op Fl l Ar user 48.Op Fl n Ar tracefile 49.Op Fl s Ar src_addr 50.Op Fl P Ar policy 51.Oo 52.Ar host 53.Op Ar port 54.Oc 55.Sh DESCRIPTION 56The 57.Nm 58command 59is used to communicate with another host using the 60.Tn TELNET 61protocol. 62If 63.Nm 64is invoked without the 65.Ar host 66argument, it enters command mode, 67indicated by its prompt 68.Pq Dq Li telnet\&> . 69In this mode, it accepts and executes the commands listed below. 70If it is invoked with arguments, it performs an 71.Ic open 72command with those arguments. 73.Pp 74Options: 75.Bl -tag -width indent 76.It Fl 4 77Forces 78.Nm 79to use IPv4 addresses only. 80.It Fl 6 81Forces 82.Nm 83to use IPv6 addresses only. 84.It Fl 8 85Specifies an 8-bit data path. 86This causes an attempt to 87negotiate the 88.Dv TELNET BINARY 89option on both input and output. 90.It Fl B Ar baudrate 91Sets the baud rate to 92.Ar baudrate . 93.It Fl E 94Stops any character from being recognized as an escape character. 95.It Fl F 96If Kerberos V5 authentication is being used, the 97.Fl F 98option allows the local credentials to be forwarded 99to the remote system, including any credentials that 100have already been forwarded into the local environment. 101.It Fl K 102Specifies no automatic login to the remote system. 103.It Fl L 104Specifies an 8-bit data path on output. 105This causes the 106.Dv BINARY 107option to be negotiated on output. 108.It Fl N 109Prevents IP address to name lookup when destination host is given 110as an IP address. 111.It Fl S Ar tos 112Sets the IP type-of-service (TOS) option for the telnet 113connection to the value 114.Ar tos , 115which can be a numeric TOS value 116or, on systems that support it, a symbolic 117TOS name found in the 118.Pa /etc/iptos 119file. 120.It Fl X Ar atype 121Disables the 122.Ar atype 123type of authentication. 124.It Fl a 125Attempt automatic login. 126This is now the default, so this option is ignored. 127Currently, this sends the user name via the 128.Ev USER 129variable 130of the 131.Ev ENVIRON 132option if supported by the remote system. 133The name used is that of the current user as returned by 134.Xr getlogin 2 135if it agrees with the current user ID, 136otherwise it is the name associated with the user ID. 137.It Fl c 138Disables the reading of the user's 139.Pa \&.telnetrc 140file. 141(See the 142.Ic toggle skiprc 143command on this man page.) 144.It Fl d 145Sets the initial value of the 146.Ic debug 147toggle to 148.Dv TRUE . 149.It Fl e Ar escapechar 150Sets the initial 151.Nm 152escape character to 153.Ar escapechar . 154If 155.Ar escapechar 156is omitted, then 157there will be no escape character. 158.It Fl f 159If Kerberos V5 authentication is being used, the 160.Fl f 161option allows the local credentials to be forwarded to the remote system. 162.It Fl k Ar realm 163If Kerberos authentication is being used, the 164.Fl k 165option requests that 166.Nm 167obtain tickets for the remote host in 168realm 169.Ar realm 170instead of the remote host's realm, as determined by 171.Xr krb_realmofhost 3 . 172.It Fl l Ar user 173When connecting to the remote system, if the remote system 174understands the 175.Ev ENVIRON 176option, then 177.Ar user 178will be sent to the remote system as the value for the variable 179.Ev USER . 180This option implies the 181.Fl a 182option. 183This option may also be used with the 184.Ic open 185command. 186.It Fl n Ar tracefile 187Opens 188.Ar tracefile 189for recording trace information. 190See the 191.Ic set tracefile 192command below. 193.It Fl P Ar policy 194Use IPsec policy specification string 195.Ar policy , 196for the connections. 197See 198.Xr ipsec_set_policy 3 199for details. 200.It Fl r 201Specifies a user interface similar to 202.Xr rlogin 1 . 203In this 204mode, the escape character is set to the tilde (~) character, 205unless modified by the 206.Fl e 207option. 208.It Fl s Ar src_addr 209Set the source IP address for the 210.Nm 211connection to 212.Ar src_addr , 213which can be an IP address or a host name. 214.It Fl u 215Forces 216.Nm 217to use 218.Dv AF_UNIX 219addresses only (e.g., 220.Ux 221domain sockets, accessed with a file path). 222.It Fl x 223Turns on encryption of the data stream if possible. 224This is now the default, so this option is ignored. 225.It Fl y 226Suppresses encryption of the data stream. 227.It Ar host 228Indicates the official name, an alias, or the Internet address 229of a remote host. 230If 231.Ar host 232starts with a 233.Ql / , 234.Nm 235establishes a connection to the corresponding named socket. 236.It Ar port 237Indicates a port number (address of an application). 238If a number is 239not specified, the default 240.Nm 241port is used. 242.El 243.Pp 244When in rlogin mode, a line of the form ~.\& disconnects from the 245remote host; ~ is the 246.Nm 247escape character. 248Similarly, the line ~^Z suspends the 249.Nm 250session. 251The line ~^] escapes to the normal 252.Nm 253escape prompt. 254.Pp 255Once a connection has been opened, 256.Nm 257will attempt to enable the 258.Dv TELNET LINEMODE 259option. 260If this fails, then 261.Nm 262will revert to one of two input modes: 263either \*(Lqcharacter at a time\*(Rq 264or \*(Lqold line by line\*(Rq 265depending on what the remote system supports. 266.Pp 267When 268.Dv LINEMODE 269is enabled, character processing is done on the 270local system, under the control of the remote system. 271When input 272editing or character echoing is to be disabled, the remote system 273will relay that information. 274The remote system will also relay 275changes to any special characters that happen on the remote 276system, so that they can take effect on the local system. 277.Pp 278In \*(Lqcharacter at a time\*(Rq mode, most 279text typed is immediately sent to the remote host for processing. 280.Pp 281In \*(Lqold line by line\*(Rq mode, all text is echoed locally, 282and (normally) only completed lines are sent to the remote host. 283The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used 284to turn off and on the local echo 285(this would mostly be used to enter passwords 286without the password being echoed). 287.Pp 288If the 289.Dv LINEMODE 290option is enabled, or if the 291.Ic localchars 292toggle is 293.Dv TRUE 294(the default for \*(Lqold line by line\*(Rq; see below), 295the user's 296.Ic quit , 297.Ic intr , 298and 299.Ic flush 300characters are trapped locally, and sent as 301.Tn TELNET 302protocol sequences to the remote side. 303If 304.Dv LINEMODE 305has ever been enabled, then the user's 306.Ic susp 307and 308.Ic eof 309are also sent as 310.Tn TELNET 311protocol sequences, 312and 313.Ic quit 314is sent as a 315.Dv TELNET ABORT 316instead of 317.Dv BREAK . 318There are options (see 319.Ic toggle 320.Ic autoflush 321and 322.Ic toggle 323.Ic autosynch 324below) 325which cause this action to flush subsequent output to the terminal 326(until the remote host acknowledges the 327.Tn TELNET 328sequence) and flush previous terminal input 329(in the case of 330.Ic quit 331and 332.Ic intr ) . 333.Pp 334While connected to a remote host, 335.Nm 336command mode may be entered by typing the 337.Nm 338\*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). 339When in command mode, the normal terminal editing conventions are available. 340.Pp 341The following 342.Nm 343commands are available. 344Only enough of each command to uniquely identify it need be typed 345(this is also true for arguments to the 346.Ic mode , 347.Ic set , 348.Ic toggle , 349.Ic unset , 350.Ic slc , 351.Ic environ , 352and 353.Ic display 354commands). 355.Bl -tag -width "mode type" 356.It Ic auth Ar argument ... 357The auth command manipulates the information sent through the 358.Dv TELNET AUTHENTICATE 359option. 360Valid arguments for the 361.Ic auth 362command are: 363.Bl -tag -width "disable type" 364.It Ic disable Ar type 365Disables the specified type of authentication. 366To 367obtain a list of available types, use the 368.Ic auth disable ?\& 369command. 370.It Ic enable Ar type 371Enables the specified type of authentication. 372To 373obtain a list of available types, use the 374.Ic auth enable ?\& 375command. 376.It Ic status 377Lists the current status of the various types of 378authentication. 379.El 380.It Ic close 381Close a 382.Tn TELNET 383session and return to command mode. 384.It Ic display Ar argument ... 385Displays all, or some, of the 386.Ic set 387and 388.Ic toggle 389values (see below). 390.It Ic encrypt Ar argument ... 391The encrypt command manipulates the information sent through the 392.Dv TELNET ENCRYPT 393option. 394.Pp 395Valid arguments for the 396.Ic encrypt 397command are: 398.Bl -tag -width Ar 399.It Ic disable Ar type Xo 400.Op Cm input | output 401.Xc 402Disables the specified type of encryption. 403If you 404omit the input and output, both input and output 405are disabled. 406To obtain a list of available 407types, use the 408.Ic encrypt disable ?\& 409command. 410.It Ic enable Ar type Xo 411.Op Cm input | output 412.Xc 413Enables the specified type of encryption. 414If you 415omit input and output, both input and output are 416enabled. 417To obtain a list of available types, use the 418.Ic encrypt enable ?\& 419command. 420.It Ic input 421This is the same as the 422.Ic encrypt start input 423command. 424.It Ic -input 425This is the same as the 426.Ic encrypt stop input 427command. 428.It Ic output 429This is the same as the 430.Ic encrypt start output 431command. 432.It Ic -output 433This is the same as the 434.Ic encrypt stop output 435command. 436.It Ic start Op Cm input | output 437Attempts to start encryption. 438If you omit 439.Ic input 440and 441.Ic output , 442both input and output are enabled. 443To 444obtain a list of available types, use the 445.Ic encrypt enable ?\& 446command. 447.It Ic status 448Lists the current status of encryption. 449.It Ic stop Op Cm input | output 450Stops encryption. 451If you omit input and output, 452encryption is on both input and output. 453.It Ic type Ar type 454Sets the default type of encryption to be used 455with later 456.Ic encrypt start 457or 458.Ic encrypt stop 459commands. 460.El 461.It Ic environ Ar arguments ... 462The 463.Ic environ 464command is used to manipulate the 465variables that may be sent through the 466.Dv TELNET ENVIRON 467option. 468The initial set of variables is taken from the users 469environment, with only the 470.Ev DISPLAY 471and 472.Ev PRINTER 473variables being exported by default. 474The 475.Ev USER 476variable is also exported if the 477.Fl a 478or 479.Fl l 480options are used. 481.Pp 482Valid arguments for the 483.Ic environ 484command are: 485.Bl -tag -width Fl 486.It Ic define Ar variable value 487Define the variable 488.Ar variable 489to have a value of 490.Ar value . 491Any variables defined by this command are automatically exported. 492The 493.Ar value 494may be enclosed in single or double quotes so 495that tabs and spaces may be included. 496.It Ic undefine Ar variable 497Remove 498.Ar variable 499from the list of environment variables. 500.It Ic export Ar variable 501Mark the variable 502.Ar variable 503to be exported to the remote side. 504.It Ic unexport Ar variable 505Mark the variable 506.Ar variable 507to not be exported unless 508explicitly asked for by the remote side. 509.It Ic list 510List the current set of environment variables. 511Those marked with a 512.Cm * 513will be sent automatically, 514other variables will only be sent if explicitly requested. 515.It Ic ?\& 516Prints out help information for the 517.Ic environ 518command. 519.El 520.It Ic logout 521Sends the 522.Dv TELNET LOGOUT 523option to the remote side. 524This command is similar to a 525.Ic close 526command; however, if the remote side does not support the 527.Dv LOGOUT 528option, nothing happens. 529If, however, the remote side does support the 530.Dv LOGOUT 531option, this command should cause the remote side to close the 532.Tn TELNET 533connection. 534If the remote side also supports the concept of 535suspending a user's session for later reattachment, 536the logout argument indicates that you 537should terminate the session immediately. 538.It Ic mode Ar type 539.Ar Type 540is one of several options, depending on the state of the 541.Tn TELNET 542session. 543The remote host is asked for permission to go into the requested mode. 544If the remote host is capable of entering that mode, the requested 545mode will be entered. 546.Bl -tag -width Ar 547.It Ic character 548Disable the 549.Dv TELNET LINEMODE 550option, or, if the remote side does not understand the 551.Dv LINEMODE 552option, then enter \*(Lqcharacter at a time\*(Rq mode. 553.It Ic line 554Enable the 555.Dv TELNET LINEMODE 556option, or, if the remote side does not understand the 557.Dv LINEMODE 558option, then attempt to enter \*(Lqold-line-by-line\*(Rq mode. 559.It Ic isig Pq Ic \-isig 560Attempt to enable (disable) the 561.Dv TRAPSIG 562mode of the 563.Dv LINEMODE 564option. 565This requires that the 566.Dv LINEMODE 567option be enabled. 568.It Ic edit Pq Ic \-edit 569Attempt to enable (disable) the 570.Dv EDIT 571mode of the 572.Dv LINEMODE 573option. 574This requires that the 575.Dv LINEMODE 576option be enabled. 577.It Ic softtabs Pq Ic \-softtabs 578Attempt to enable (disable) the 579.Dv SOFT_TAB 580mode of the 581.Dv LINEMODE 582option. 583This requires that the 584.Dv LINEMODE 585option be enabled. 586.It Ic litecho Pq Ic \-litecho 587Attempt to enable (disable) the 588.Dv LIT_ECHO 589mode of the 590.Dv LINEMODE 591option. 592This requires that the 593.Dv LINEMODE 594option be enabled. 595.It Ic ?\& 596Prints out help information for the 597.Ic mode 598command. 599.El 600.It Xo 601.Ic open 602.Op Fl l Ar user 603.Op Ar host 604.Op Oo Fl /+ Oc Ns Ar port 605.Xc 606Open a connection to the named host. 607If no port number 608is specified, 609.Nm 610will attempt to contact a 611.Tn TELNET 612server at the default port. 613The host specification may be either a host name (see 614.Xr hosts 5 ) , 615an Internet address specified in the \*(Lqdot notation\*(Rq (see 616.Xr inet 3 ) , 617or IPv6 host name or IPv6 coloned-hexadecimal addreess. 618The 619.Fl l 620option may be used to specify the user name 621to be passed to the remote system via the 622.Ev ENVIRON 623option. 624When connecting to a non-standard port, 625.Nm 626omits any automatic initiation of 627.Tn TELNET 628options. 629When the port number is preceded by a minus sign, 630the initial option negotiation is done. 631When, however, the port number 632is preceded by a plus sign, 633any option negotiation and understanding is prohibited, 634making telnet dumb client for POP3/SMTP/NNTP/HTTP-like 635protocols with any data including 636.Tn TELNET 637IAC character (0xff). 638After establishing a connection, the file 639.Pa \&.telnetrc 640in the 641users home directory is opened. 642Lines beginning with a # are 643comment lines. 644Blank lines are ignored. 645Lines that begin 646without white space are the start of a machine entry. 647The 648first thing on the line is the name of the machine that is 649being connected to. 650It may be the hostname or numeric address specified as the argument 651.Ar host , 652the canonical name of that string as determined by 653.Xr getaddrinfo 3 , 654or the string 655.Dq Li DEFAULT 656indicating all hosts. 657The rest of the line, and successive 658lines that begin with white space are assumed to be 659.Nm 660commands and are processed as if they had been typed 661in manually to the 662.Nm 663command prompt. 664.It Ic quit 665Close any open 666.Tn TELNET 667session and exit 668.Nm . 669An end of file (in command mode) will also close a session and exit. 670.It Ic send Ar arguments 671Sends one or more special character sequences to the remote host. 672The following are the arguments which may be specified 673(more than one argument may be specified at a time): 674.Bl -tag -width escape 675.It Ic abort 676Sends the 677.Dv TELNET ABORT 678(Abort 679processes) 680sequence. 681.It Ic ao 682Sends the 683.Dv TELNET AO 684(Abort Output) sequence, which should cause the remote system to flush 685all output 686.Em from 687the remote system 688.Em to 689the user's terminal. 690.It Ic ayt 691Sends the 692.Dv TELNET AYT 693(Are You There) 694sequence, to which the remote system may or may not choose to respond. 695.It Ic brk 696Sends the 697.Dv TELNET BRK 698(Break) sequence, which may have significance to the remote 699system. 700.It Ic ec 701Sends the 702.Dv TELNET EC 703(Erase Character) 704sequence, which should cause the remote system to erase the last character 705entered. 706.It Ic el 707Sends the 708.Dv TELNET EL 709(Erase Line) 710sequence, which should cause the remote system to erase the line currently 711being entered. 712.It Ic eof 713Sends the 714.Dv TELNET EOF 715(End Of File) 716sequence. 717.It Ic eor 718Sends the 719.Dv TELNET EOR 720(End of Record) 721sequence. 722.It Ic escape 723Sends the current 724.Nm 725escape character (initially \*(Lq^\*(Rq). 726.It Ic ga 727Sends the 728.Dv TELNET GA 729(Go Ahead) 730sequence, which likely has no significance to the remote system. 731.It Ic getstatus 732If the remote side supports the 733.Dv TELNET STATUS 734command, 735.Ic getstatus 736will send the subnegotiation to request that the server send 737its current option status. 738.It Ic ip 739Sends the 740.Dv TELNET IP 741(Interrupt Process) sequence, which should cause the remote 742system to abort the currently running process. 743.It Ic nop 744Sends the 745.Dv TELNET NOP 746(No OPeration) 747sequence. 748.It Ic susp 749Sends the 750.Dv TELNET SUSP 751(SUSPend process) 752sequence. 753.It Ic synch 754Sends the 755.Dv TELNET SYNCH 756sequence. 757This sequence causes the remote system to discard all previously typed 758(but not yet read) input. 759This sequence is sent as 760.Tn TCP 761urgent 762data (and may not work if the remote system is a 763.Bx 4.2 764system -- if 765it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). 766.It Ic do Ar cmd 767.It Ic dont Ar cmd 768.It Ic will Ar cmd 769.It Ic wont Ar cmd 770Sends the 771.Dv TELNET DO 772.Ar cmd 773sequence. 774.Ar Cmd 775can be either a decimal number between 0 and 255, 776or a symbolic name for a specific 777.Dv TELNET 778command. 779.Ar Cmd 780can also be either 781.Ic help 782or 783.Ic ?\& 784to print out help information, including 785a list of known symbolic names. 786.It Ic ?\& 787Prints out help information for the 788.Ic send 789command. 790.El 791.It Ic set Ar argument value 792.It Ic unset Ar argument value 793The 794.Ic set 795command will set any one of a number of 796.Nm 797variables to a specific value or to 798.Dv TRUE . 799The special value 800.Ic off 801turns off the function associated with 802the variable, this is equivalent to using the 803.Ic unset 804command. 805The 806.Ic unset 807command will disable or set to 808.Dv FALSE 809any of the specified functions. 810The values of variables may be interrogated with the 811.Ic display 812command. 813The variables which may be set or unset, but not toggled, are 814listed here. 815In addition, any of the variables for the 816.Ic toggle 817command may be explicitly set or unset using 818the 819.Ic set 820and 821.Ic unset 822commands. 823.Bl -tag -width escape 824.It Ic ayt 825If 826.Tn TELNET 827is in localchars mode, or 828.Dv LINEMODE 829is enabled, and the status character is typed, a 830.Dv TELNET AYT 831sequence (see 832.Ic send ayt 833preceding) is sent to the 834remote host. 835The initial value for the \*(LqAre You There\*(Rq 836character is the terminal's status character. 837.It Ic echo 838This is the value (initially \*(Lq^E\*(Rq) which, when in 839\*(Lqline by line\*(Rq mode, toggles between doing local echoing 840of entered characters (for normal processing), and suppressing 841echoing of entered characters (for entering, say, a password). 842.It Ic eof 843If 844.Nm 845is operating in 846.Dv LINEMODE 847or \*(Lqold line by line\*(Rq mode, entering this character 848as the first character on a line will cause this character to be 849sent to the remote system. 850The initial value of the eof character is taken to be the terminal's 851.Ic eof 852character. 853.It Ic erase 854If 855.Nm 856is in 857.Ic localchars 858mode (see 859.Ic toggle 860.Ic localchars 861below), 862.Sy and 863if 864.Nm 865is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 866character is typed, a 867.Dv TELNET EC 868sequence (see 869.Ic send 870.Ic ec 871above) 872is sent to the remote system. 873The initial value for the erase character is taken to be 874the terminal's 875.Ic erase 876character. 877.It Ic escape 878This is the 879.Nm 880escape character (initially \*(Lq^[\*(Rq) which causes entry 881into 882.Nm 883command mode (when connected to a remote system). 884.It Ic flushoutput 885If 886.Nm 887is in 888.Ic localchars 889mode (see 890.Ic toggle 891.Ic localchars 892below) 893and the 894.Ic flushoutput 895character is typed, a 896.Dv TELNET AO 897sequence (see 898.Ic send 899.Ic ao 900above) 901is sent to the remote host. 902The initial value for the flush character is taken to be 903the terminal's 904.Ic flush 905character. 906.It Ic forw1 907.It Ic forw2 908If 909.Nm 910is operating in 911.Dv LINEMODE , 912these are the 913characters that, when typed, cause partial lines to be 914forwarded to the remote system. 915The initial value for 916the forwarding characters are taken from the terminal's 917eol and eol2 characters. 918.It Ic interrupt 919If 920.Nm 921is in 922.Ic localchars 923mode (see 924.Ic toggle 925.Ic localchars 926below) 927and the 928.Ic interrupt 929character is typed, a 930.Dv TELNET IP 931sequence (see 932.Ic send 933.Ic ip 934above) 935is sent to the remote host. 936The initial value for the interrupt character is taken to be 937the terminal's 938.Ic intr 939character. 940.It Ic kill 941If 942.Nm 943is in 944.Ic localchars 945mode (see 946.Ic toggle 947.Ic localchars 948below), 949.Ic and 950if 951.Nm 952is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 953character is typed, a 954.Dv TELNET EL 955sequence (see 956.Ic send 957.Ic el 958above) 959is sent to the remote system. 960The initial value for the kill character is taken to be 961the terminal's 962.Ic kill 963character. 964.It Ic lnext 965If 966.Nm 967is operating in 968.Dv LINEMODE 969or \*(Lqold line by line\*(Rq mode, then this character is taken to 970be the terminal's 971.Ic lnext 972character. 973The initial value for the lnext character is taken to be 974the terminal's 975.Ic lnext 976character. 977.It Ic quit 978If 979.Nm 980is in 981.Ic localchars 982mode (see 983.Ic toggle 984.Ic localchars 985below) 986and the 987.Ic quit 988character is typed, a 989.Dv TELNET BRK 990sequence (see 991.Ic send 992.Ic brk 993above) 994is sent to the remote host. 995The initial value for the quit character is taken to be 996the terminal's 997.Ic quit 998character. 999.It Ic reprint 1000If 1001.Nm 1002is operating in 1003.Dv LINEMODE 1004or \*(Lqold line by line\*(Rq mode, then this character is taken to 1005be the terminal's 1006.Ic reprint 1007character. 1008The initial value for the reprint character is taken to be 1009the terminal's 1010.Ic reprint 1011character. 1012.It Ic rlogin 1013This is the rlogin escape character. 1014If set, the normal 1015.Nm 1016escape character is ignored unless it is 1017preceded by this character at the beginning of a line. 1018This character, at the beginning of a line followed by 1019a "." closes the connection; when followed by a ^Z it 1020suspends the 1021.Nm 1022command. 1023The initial state is to 1024disable the 1025.Nm rlogin 1026escape character. 1027.It Ic start 1028If the 1029.Dv TELNET TOGGLE-FLOW-CONTROL 1030option has been enabled, 1031then this character is taken to 1032be the terminal's 1033.Ic start 1034character. 1035The initial value for the start character is taken to be 1036the terminal's 1037.Ic start 1038character. 1039.It Ic stop 1040If the 1041.Dv TELNET TOGGLE-FLOW-CONTROL 1042option has been enabled, 1043then this character is taken to 1044be the terminal's 1045.Ic stop 1046character. 1047The initial value for the stop character is taken to be 1048the terminal's 1049.Ic stop 1050character. 1051.It Ic susp 1052If 1053.Nm 1054is in 1055.Ic localchars 1056mode, or 1057.Dv LINEMODE 1058is enabled, and the 1059.Ic suspend 1060character is typed, a 1061.Dv TELNET SUSP 1062sequence (see 1063.Ic send 1064.Ic susp 1065above) 1066is sent to the remote host. 1067The initial value for the suspend character is taken to be 1068the terminal's 1069.Ic suspend 1070character. 1071.It Ic tracefile 1072This is the file to which the output, caused by 1073.Ic netdata 1074or 1075.Ic option 1076tracing being 1077.Dv TRUE , 1078will be written. 1079If it is set to 1080.Dq Fl , 1081then tracing information will be written to standard output (the default). 1082.It Ic worderase 1083If 1084.Nm 1085is operating in 1086.Dv LINEMODE 1087or \*(Lqold line by line\*(Rq mode, then this character is taken to 1088be the terminal's 1089.Ic worderase 1090character. 1091The initial value for the worderase character is taken to be 1092the terminal's 1093.Ic worderase 1094character. 1095.It Ic ?\& 1096Displays the legal 1097.Ic set 1098.Pq Ic unset 1099commands. 1100.El 1101.It Ic opie Ar sequence challenge 1102The 1103.Ic opie 1104command computes a response to the OPIE challenge. 1105.It Ic slc Ar state 1106The 1107.Ic slc 1108command (Set Local Characters) is used to set 1109or change the state of the special 1110characters when the 1111.Dv TELNET LINEMODE 1112option has 1113been enabled. 1114Special characters are characters that get 1115mapped to 1116.Tn TELNET 1117commands sequences (like 1118.Ic ip 1119or 1120.Ic quit ) 1121or line editing characters (like 1122.Ic erase 1123and 1124.Ic kill ) . 1125By default, the local special characters are exported. 1126.Bl -tag -width Fl 1127.It Ic check 1128Verify the current settings for the current special characters. 1129The remote side is requested to send all the current special 1130character settings, and if there are any discrepancies with 1131the local side, the local side will switch to the remote value. 1132.It Ic export 1133Switch to the local defaults for the special characters. 1134The 1135local default characters are those of the local terminal at 1136the time when 1137.Nm 1138was started. 1139.It Ic import 1140Switch to the remote defaults for the special characters. 1141The remote default characters are those of the remote system 1142at the time when the 1143.Tn TELNET 1144connection was established. 1145.It Ic ?\& 1146Prints out help information for the 1147.Ic slc 1148command. 1149.El 1150.It Ic status 1151Show the current status of 1152.Nm . 1153This includes the peer one is connected to, as well 1154as the current mode. 1155.It Ic toggle Ar arguments ... 1156Toggle (between 1157.Dv TRUE 1158and 1159.Dv FALSE ) 1160various flags that control how 1161.Nm 1162responds to events. 1163These flags may be set explicitly to 1164.Dv TRUE 1165or 1166.Dv FALSE 1167using the 1168.Ic set 1169and 1170.Ic unset 1171commands listed above. 1172More than one argument may be specified. 1173The state of these flags may be interrogated with the 1174.Ic display 1175command. 1176Valid arguments are: 1177.Bl -tag -width Ar 1178.It Ic authdebug 1179Turns on debugging information for the authentication code. 1180.It Ic autoflush 1181If 1182.Ic autoflush 1183and 1184.Ic localchars 1185are both 1186.Dv TRUE , 1187then when the 1188.Ic ao , 1189or 1190.Ic quit 1191characters are recognized (and transformed into 1192.Tn TELNET 1193sequences; see 1194.Ic set 1195above for details), 1196.Nm 1197refuses to display any data on the user's terminal 1198until the remote system acknowledges (via a 1199.Dv TELNET TIMING MARK 1200option) 1201that it has processed those 1202.Tn TELNET 1203sequences. 1204The initial value for this toggle is 1205.Dv TRUE 1206if the terminal user had not 1207done an "stty noflsh", otherwise 1208.Dv FALSE 1209(see 1210.Xr stty 1 ) . 1211.It Ic autodecrypt 1212When the 1213.Dv TELNET ENCRYPT 1214option is negotiated, by 1215default the actual encryption (decryption) of the data 1216stream does not start automatically. 1217The autoencrypt 1218(autodecrypt) command states that encryption of the 1219output (input) stream should be enabled as soon as 1220possible. 1221.It Ic autologin 1222If the remote side supports the 1223.Dv TELNET AUTHENTICATION 1224option 1225.Nm 1226attempts to use it to perform automatic authentication. 1227If the 1228.Dv AUTHENTICATION 1229option is not supported, the user's login 1230name are propagated through the 1231.Dv TELNET ENVIRON 1232option. 1233This command is the same as specifying 1234.Fl a 1235option on the 1236.Ic open 1237command. 1238.It Ic autosynch 1239If 1240.Ic autosynch 1241and 1242.Ic localchars 1243are both 1244.Dv TRUE , 1245then when either the 1246.Ic intr 1247or 1248.Ic quit 1249characters is typed (see 1250.Ic set 1251above for descriptions of the 1252.Ic intr 1253and 1254.Ic quit 1255characters), the resulting 1256.Tn TELNET 1257sequence sent is followed by the 1258.Dv TELNET SYNCH 1259sequence. 1260This procedure 1261.Ic should 1262cause the remote system to begin throwing away all previously 1263typed input until both of the 1264.Tn TELNET 1265sequences have been read and acted upon. 1266The initial value of this toggle is 1267.Dv FALSE . 1268.It Ic binary 1269Enable or disable the 1270.Dv TELNET BINARY 1271option on both input and output. 1272.It Ic inbinary 1273Enable or disable the 1274.Dv TELNET BINARY 1275option on input. 1276.It Ic outbinary 1277Enable or disable the 1278.Dv TELNET BINARY 1279option on output. 1280.It Ic crlf 1281If this is 1282.Dv TRUE , 1283then carriage returns will be sent as 1284.Li <CR><LF> . 1285If this is 1286.Dv FALSE , 1287then carriage returns will be send as 1288.Li <CR><NUL> . 1289The initial value for this toggle is 1290.Dv FALSE . 1291.It Ic crmod 1292Toggle carriage return mode. 1293When this mode is enabled, most carriage return characters received from 1294the remote host will be mapped into a carriage return followed by 1295a line feed. 1296This mode does not affect those characters typed by the user, only 1297those received from the remote host. 1298This mode is not very useful unless the remote host 1299only sends carriage return, but never line feed. 1300The initial value for this toggle is 1301.Dv FALSE . 1302.It Ic debug 1303Toggles socket level debugging (useful only to the 1304.Ic super user ) . 1305The initial value for this toggle is 1306.Dv FALSE . 1307.It Ic encdebug 1308Turns on debugging information for the encryption code. 1309.It Ic localchars 1310If this is 1311.Dv TRUE , 1312then the 1313.Ic flush , 1314.Ic interrupt , 1315.Ic quit , 1316.Ic erase , 1317and 1318.Ic kill 1319characters (see 1320.Ic set 1321above) are recognized locally, and transformed into (hopefully) appropriate 1322.Tn TELNET 1323control sequences 1324(respectively 1325.Ic ao , 1326.Ic ip , 1327.Ic brk , 1328.Ic ec , 1329and 1330.Ic el ; 1331see 1332.Ic send 1333above). 1334The initial value for this toggle is 1335.Dv TRUE 1336in \*(Lqold line by line\*(Rq mode, 1337and 1338.Dv FALSE 1339in \*(Lqcharacter at a time\*(Rq mode. 1340When the 1341.Dv LINEMODE 1342option is enabled, the value of 1343.Ic localchars 1344is ignored, and assumed to always be 1345.Dv TRUE . 1346If 1347.Dv LINEMODE 1348has ever been enabled, then 1349.Ic quit 1350is sent as 1351.Ic abort , 1352and 1353.Ic eof 1354and 1355.Ic suspend 1356are sent as 1357.Ic eof 1358and 1359.Ic susp 1360(see 1361.Ic send 1362above). 1363.It Ic netdata 1364Toggles the display of all network data (in hexadecimal format). 1365The initial value for this toggle is 1366.Dv FALSE . 1367.It Ic options 1368Toggles the display of some internal 1369.Nm 1370protocol processing (having to do with 1371.Tn TELNET 1372options). 1373The initial value for this toggle is 1374.Dv FALSE . 1375.It Ic prettydump 1376When the 1377.Ic netdata 1378toggle is enabled, if 1379.Ic prettydump 1380is enabled the output from the 1381.Ic netdata 1382command will be formatted in a more user readable format. 1383Spaces are put between each character in the output, and the 1384beginning of any 1385.Nm 1386escape sequence is preceded by a '*' to aid in locating them. 1387.It Ic skiprc 1388When the skiprc toggle is 1389.Dv TRUE , 1390.Nm 1391skips the reading of the 1392.Pa \&.telnetrc 1393file in the users home 1394directory when connections are opened. 1395The initial 1396value for this toggle is 1397.Dv FALSE . 1398.It Ic termdata 1399Toggles the display of all terminal data (in hexadecimal format). 1400The initial value for this toggle is 1401.Dv FALSE . 1402.It Ic verbose_encrypt 1403When the 1404.Ic verbose_encrypt 1405toggle is 1406.Dv TRUE , 1407.Nm 1408prints out a message each time encryption is enabled or 1409disabled. 1410The initial value for this toggle is 1411.Dv FALSE . 1412.It Ic ?\& 1413Displays the legal 1414.Ic toggle 1415commands. 1416.El 1417.It Ic z 1418Suspend 1419.Nm . 1420This command only works when the user is using the 1421.Xr csh 1 . 1422.It Ic \&! Op Ar command 1423Execute a single command in a subshell on the local 1424system. 1425If 1426.Ar command 1427is omitted, then an interactive 1428subshell is invoked. 1429.It Ic ?\& Op Ar command 1430Get help. 1431With no arguments, 1432.Nm 1433prints a help summary. 1434If 1435.Ar command 1436is specified, 1437.Nm 1438will print the help information for just that command. 1439.El 1440.Sh ENVIRONMENT 1441.Nm 1442uses at least the 1443.Ev HOME , 1444.Ev SHELL , 1445.Ev DISPLAY , 1446and 1447.Ev TERM 1448environment variables. 1449Other environment variables may be propagated 1450to the other side via the 1451.Dv TELNET ENVIRON 1452option. 1453.Sh FILES 1454.Bl -tag -width ~/.telnetrc -compact 1455.It Pa ~/.telnetrc 1456user customized telnet startup values 1457.El 1458.Sh SEE ALSO 1459.Xr rlogin 1 , 1460.Xr rsh 1 , 1461.Xr hosts 5 , 1462.Xr nologin 5 , 1463.Xr telnetd 8 1464.Sh HISTORY 1465The 1466.Nm 1467command appeared in 1468.Bx 4.2 . 1469.Pp 1470IPv6 support was added by WIDE/KAME project. 1471.Sh NOTES 1472On some remote systems, echo has to be turned off manually when in 1473\*(Lqold line by line\*(Rq mode. 1474.Pp 1475In \*(Lqold line by line\*(Rq mode or 1476.Dv LINEMODE 1477the terminal's 1478.Ic eof 1479character is only recognized (and sent to the remote system) 1480when it is the first character on a line. 1481