1.\" Copyright (c) 1983, 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.roff% 5.\" 6.\" @(#)telnet.1 8.4 (Berkeley) 02/03/94 7.\" 8.Dd 9.Dt TELNET 1 10.Os BSD 4.2 11.Sh NAME 12.Nm telnet 13.Nd user interface to the 14.Tn TELNET 15protocol 16.Sh SYNOPSIS 17.Nm telnet 18.Op Fl 8 19.Op Fl E 20.Op Fl F 21.Op Fl K 22.Op Fl L 23.Op Fl S Ar tos 24.Op Fl X Ar authtype 25.Op Fl a 26.Op Fl c 27.Op Fl d 28.Op Fl e Ar escapechar 29.Op Fl f 30.Op Fl k Ar realm 31.Op Fl l Ar user 32.Op Fl n Ar tracefile 33.Op Fl r 34.Op Fl x 35.Oo 36.Ar host 37.Op port 38.Oc 39.Sh DESCRIPTION 40The 41.Nm telnet 42command 43is used to communicate with another host using the 44.Tn TELNET 45protocol. 46If 47.Nm telnet 48is invoked without the 49.Ar host 50argument, it enters command mode, 51indicated by its prompt 52.Pq Nm telnet\&> . 53In this mode, it accepts and executes the commands listed below. 54If it is invoked with arguments, it performs an 55.Ic open 56command with those arguments. 57.Pp 58Options: 59.Bl -tag -width indent 60.It Fl 8 61Specifies an 8-bit data path. This causes an attempt to 62negotiate the 63.Dv TELNET BINARY 64option on both input and output. 65.It Fl E 66Stops any character from being recognized as an escape character. 67.It Fl F 68If Kerberos V5 authentication is being used, the 69.Fl F 70option allows the local credentials to be forwarded 71to the remote system, including any credentials that 72have already been forwarded into the local environment. 73.It Fl K 74Specifies no automatic login to the remote system. 75.It Fl L 76Specifies an 8-bit data path on output. This causes the 77BINARY option to be negotiated on output. 78.It Fl S Ar tos 79Sets the IP type-of-service (TOS) option for the telnet 80connection to the value 81.Ar tos, 82which can be a numeric TOS value 83or, on systems that support it, a symbolic 84TOS name found in the /etc/iptos file. 85.It Fl X Ar atype 86Disables the 87.Ar atype 88type of authentication. 89.It Fl a 90Attempt automatic login. 91Currently, this sends the user name via the 92.Ev USER 93variable 94of the 95.Ev ENVIRON 96option if supported by the remote system. 97The name used is that of the current user as returned by 98.Xr getlogin 2 99if it agrees with the current user ID, 100otherwise it is the name associated with the user ID. 101.It Fl c 102Disables the reading of the user's 103.Pa \&.telnetrc 104file. (See the 105.Ic toggle skiprc 106command on this man page.) 107.It Fl d 108Sets the initial value of the 109.Ic debug 110toggle to 111.Dv TRUE 112.It Fl e Ar escape char 113Sets the initial 114.Nm 115.Nm telnet 116escape character to 117.Ar escape char. 118If 119.Ar escape char 120is omitted, then 121there will be no escape character. 122.It Fl f 123If Kerberos V5 authentication is being used, the 124.Fl f 125option allows the local credentials to be forwarded to the remote system. 126.It Fl k Ar realm 127If Kerberos authentication is being used, the 128.Fl k 129option requests that telnet obtain tickets for the remote host in 130realm realm instead of the remote host's realm, as determined 131by 132.Xr krb_realmofhost 3 . 133.It Fl l Ar user 134When connecting to the remote system, if the remote system 135understands the 136.Ev ENVIRON 137option, then 138.Ar user 139will be sent to the remote system as the value for the variable USER. 140This option implies the 141.Fl a 142option. 143This option may also be used with the 144.Ic open 145command. 146.It Fl n Ar tracefile 147Opens 148.Ar tracefile 149for recording trace information. 150See the 151.Ic set tracefile 152command below. 153.It Fl r 154Specifies a user interface similar to 155.Xr rlogin 1 . 156In this 157mode, the escape character is set to the tilde (~) character, 158unless modified by the -e option. 159.It Fl x 160Turns on encryption of the data stream if possible. This 161option is not available outside of the United States and 162Canada. 163.It Ar host 164Indicates the official name, an alias, or the Internet address 165of a remote host. 166.It Ar port 167Indicates a port number (address of an application). If a number is 168not specified, the default 169.Nm telnet 170port is used. 171.El 172.Pp 173When in rlogin mode, a line of the form ~. disconnects from the 174remote host; ~ is the telnet escape character. 175Similarly, the line ~^Z suspends the telnet session. 176The line ~^] escapes to the normal telnet escape prompt. 177.Pp 178Once a connection has been opened, 179.Nm telnet 180will attempt to enable the 181.Dv TELNET LINEMODE 182option. 183If this fails, then 184.Nm telnet 185will revert to one of two input modes: 186either \*(Lqcharacter at a time\*(Rq 187or \*(Lqold line by line\*(Rq 188depending on what the remote system supports. 189.Pp 190When 191.Dv LINEMODE 192is enabled, character processing is done on the 193local system, under the control of the remote system. When input 194editing or character echoing is to be disabled, the remote system 195will relay that information. The remote system will also relay 196changes to any special characters that happen on the remote 197system, so that they can take effect on the local system. 198.Pp 199In \*(Lqcharacter at a time\*(Rq mode, most 200text typed is immediately sent to the remote host for processing. 201.Pp 202In \*(Lqold line by line\*(Rq mode, all text is echoed locally, 203and (normally) only completed lines are sent to the remote host. 204The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used 205to turn off and on the local echo 206(this would mostly be used to enter passwords 207without the password being echoed). 208.Pp 209If the 210.Dv LINEMODE 211option is enabled, or if the 212.Ic localchars 213toggle is 214.Dv TRUE 215(the default for \*(Lqold line by line\*(Lq; see below), 216the user's 217.Ic quit , 218.Ic intr , 219and 220.Ic flush 221characters are trapped locally, and sent as 222.Tn TELNET 223protocol sequences to the remote side. 224If 225.Dv LINEMODE 226has ever been enabled, then the user's 227.Ic susp 228and 229.Ic eof 230are also sent as 231.Tn TELNET 232protocol sequences, 233and 234.Ic quit 235is sent as a 236.Dv TELNET ABORT 237instead of 238.Dv BREAK 239There are options (see 240.Ic toggle 241.Ic autoflush 242and 243.Ic toggle 244.Ic autosynch 245below) 246which cause this action to flush subsequent output to the terminal 247(until the remote host acknowledges the 248.Tn TELNET 249sequence) and flush previous terminal input 250(in the case of 251.Ic quit 252and 253.Ic intr ) . 254.Pp 255While connected to a remote host, 256.Nm telnet 257command mode may be entered by typing the 258.Nm telnet 259\*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). 260When in command mode, the normal terminal editing conventions are available. 261.Pp 262The following 263.Nm telnet 264commands are available. 265Only enough of each command to uniquely identify it need be typed 266(this is also true for arguments to the 267.Ic mode , 268.Ic set , 269.Ic toggle , 270.Ic unset , 271.Ic slc , 272.Ic environ , 273and 274.Ic display 275commands). 276.Pp 277.Bl -tag -width "mode type" 278.It Ic auth Ar argument ... 279The auth command manipulates the information sent through the 280.Dv TELNET AUTHENTICATE 281option. Valid arguments for the 282auth command are as follows: 283.Bl -tag -width "disable type" 284.It Ic disable Ar type 285Disables the specified type of authentication. To 286obtain a list of available types, use the 287.Ic auth disable \&? 288command. 289.It Ic enable Ar type 290Enables the specified type of authentication. To 291obtain a list of available types, use the 292.Ic auth enable \&? 293command. 294.It Ic status 295Lists the current status of the various types of 296authentication. 297.El 298.It Ic close 299Close a 300.Tn TELNET 301session and return to command mode. 302.It Ic display Ar argument ... 303Displays all, or some, of the 304.Ic set 305and 306.Ic toggle 307values (see below). 308.It Ic encrypt Ar argument ... 309The encrypt command manipulates the information sent through the 310.Dv TELNET ENCRYPT 311option. 312.Pp 313Note: Because of export controls, the 314.Dv TELNET ENCRYPT 315option is not supported outside of the United States and Canada. 316.Pp 317Valid arguments for the encrypt command are as follows: 318.Bl -tag -width Ar 319.It Ic disable Ar type Ic [input|output] 320Disables the specified type of encryption. If you 321omit the input and output, both input and output 322are disabled. To obtain a list of available 323types, use the 324.Ic encrypt disable \&? 325command. 326.It Ic enable Ar type Ic [input|output] 327Enables the specified type of encryption. If you 328omit input and output, both input and output are 329enabled. To obtain a list of available types, use the 330.Ic encrypt enable \&? 331command. 332.It Ic input 333This is the same as the 334.Ic encrypt start input 335command. 336.It Ic -input 337This is the same as the 338.Ic encrypt stop input 339command. 340.It Ic output 341This is the same as the 342.Ic encrypt start output 343command. 344.It Ic -output 345This is the same as the 346.Ic encrypt stop output 347command. 348.It Ic start Ic [input|output] 349Attempts to start encryption. If you omit 350.Ic input 351and 352.Ic output, 353both input and output are enabled. To 354obtain a list of available types, use the 355.Ic encrypt enable \&? 356command. 357.It Ic status 358Lists the current status of encryption. 359.It Ic stop Ic [input|output] 360Stops encryption. If you omit input and output, 361encryption is on both input and output. 362.It Ic type Ar type 363Sets the default type of encryption to be used 364with later 365.Ic encrypt start 366or 367.Ic encrypt stop 368commands. 369.El 370.It Ic environ Ar arguments... 371The 372.Ic environ 373command is used to manipulate the 374the variables that my be sent through the 375.Dv TELNET ENVIRON 376option. 377The initial set of variables is taken from the users 378environment, with only the 379.Ev DISPLAY 380and 381.Ev PRINTER 382variables being exported by default. 383The 384.Ev USER 385variable is also exported if the 386.Fl a 387or 388.Fl l 389options are used. 390.br 391Valid arguments for the 392.Ic environ 393command are: 394.Bl -tag -width Fl 395.It Ic define Ar variable value 396Define the variable 397.Ar variable 398to have a value of 399.Ar value. 400Any variables defined by this command are automatically exported. 401The 402.Ar value 403may be enclosed in single or double quotes so 404that tabs and spaces may be included. 405.It Ic undefine Ar variable 406Remove 407.Ar variable 408from the list of environment variables. 409.It Ic export Ar variable 410Mark the variable 411.Ar variable 412to be exported to the remote side. 413.It Ic unexport Ar variable 414Mark the variable 415.Ar variable 416to not be exported unless 417explicitly asked for by the remote side. 418.It Ic list 419List the current set of environment variables. 420Those marked with a 421.Cm * 422will be sent automatically, 423other variables will only be sent if explicitly requested. 424.It Ic \&? 425Prints out help information for the 426.Ic environ 427command. 428.El 429.It Ic logout 430Sends the 431.Dv TELNET LOGOUT 432option to the remote side. 433This command is similar to a 434.Ic close 435command; however, if the remote side does not support the 436.Dv LOGOUT 437option, nothing happens. 438If, however, the remote side does support the 439.Dv LOGOUT 440option, this command should cause the remote side to close the 441.Tn TELNET 442connection. 443If the remote side also supports the concept of 444suspending a user's session for later reattachment, 445the logout argument indicates that you 446should terminate the session immediately. 447.It Ic mode Ar type 448.Ar Type 449is one of several options, depending on the state of the 450.Tn TELNET 451session. 452The remote host is asked for permission to go into the requested mode. 453If the remote host is capable of entering that mode, the requested 454mode will be entered. 455.Bl -tag -width Ar 456.It Ic character 457Disable the 458.Dv TELNET LINEMODE 459option, or, if the remote side does not understand the 460.Dv LINEMODE 461option, then enter \*(Lqcharacter at a time\*(Lq mode. 462.It Ic line 463Enable the 464.Dv TELNET LINEMODE 465option, or, if the remote side does not understand the 466.Dv LINEMODE 467option, then attempt to enter \*(Lqold-line-by-line\*(Lq mode. 468.It Ic isig Pq Ic \-isig 469Attempt to enable (disable) the 470.Dv TRAPSIG 471mode of the 472.Dv LINEMODE 473option. 474This requires that the 475.Dv LINEMODE 476option be enabled. 477.It Ic edit Pq Ic \-edit 478Attempt to enable (disable) the 479.Dv EDIT 480mode of the 481.Dv LINEMODE 482option. 483This requires that the 484.Dv LINEMODE 485option be enabled. 486.It Ic softtabs Pq Ic \-softtabs 487Attempt to enable (disable) the 488.Dv SOFT_TAB 489mode of the 490.Dv LINEMODE 491option. 492This requires that the 493.Dv LINEMODE 494option be enabled. 495.It Ic litecho Pq Ic \-litecho 496Attempt to enable (disable) the 497.Dv LIT_ECHO 498mode of the 499.Dv LINEMODE 500option. 501This requires that the 502.Dv LINEMODE 503option be enabled. 504.It Ic \&? 505Prints out help information for the 506.Ic mode 507command. 508.El 509.It Xo 510.Ic open Ar host 511.Oo Op Fl l 512.Ar user 513.Oc Ns Oo Fl 514.Ar port Oc 515.Xc 516Open a connection to the named host. 517If no port number 518is specified, 519.Nm telnet 520will attempt to contact a 521.Tn TELNET 522server at the default port. 523The host specification may be either a host name (see 524.Xr hosts 5 ) 525or an Internet address specified in the \*(Lqdot notation\*(Rq (see 526.Xr inet 3 ) . 527The 528.Op Fl l 529option may be used to specify the user name 530to be passed to the remote system via the 531.Ev ENVIRON 532option. 533When connecting to a non-standard port, 534.Nm telnet 535omits any automatic initiation of 536.Tn TELNET 537options. When the port number is preceded by a minus sign, 538the initial option negotiation is done. 539After establishing a connection, the file 540.Pa \&.telnetrc 541in the 542users home directory is opened. Lines beginning with a # are 543comment lines. Blank lines are ignored. Lines that begin 544without white space are the start of a machine entry. The 545first thing on the line is the name of the machine that is 546being connected to. The rest of the line, and successive 547lines that begin with white space are assumed to be 548.Nm telnet 549commands and are processed as if they had been typed 550in manually to the 551.Nm telnet 552command prompt. 553.It Ic quit 554Close any open 555.Tn TELNET 556session and exit 557.Nm telnet . 558An end of file (in command mode) will also close a session and exit. 559.It Ic send Ar arguments 560Sends one or more special character sequences to the remote host. 561The following are the arguments which may be specified 562(more than one argument may be specified at a time): 563.Pp 564.Bl -tag -width escape 565.It Ic abort 566Sends the 567.Dv TELNET ABORT 568(Abort 569processes) 570sequence. 571.It Ic ao 572Sends the 573.Dv TELNET AO 574(Abort Output) sequence, which should cause the remote system to flush 575all output 576.Em from 577the remote system 578.Em to 579the user's terminal. 580.It Ic ayt 581Sends the 582.Dv TELNET AYT 583(Are You There) 584sequence, to which the remote system may or may not choose to respond. 585.It Ic brk 586Sends the 587.Dv TELNET BRK 588(Break) sequence, which may have significance to the remote 589system. 590.It Ic ec 591Sends the 592.Dv TELNET EC 593(Erase Character) 594sequence, which should cause the remote system to erase the last character 595entered. 596.It Ic el 597Sends the 598.Dv TELNET EL 599(Erase Line) 600sequence, which should cause the remote system to erase the line currently 601being entered. 602.It Ic eof 603Sends the 604.Dv TELNET EOF 605(End Of File) 606sequence. 607.It Ic eor 608Sends the 609.Dv TELNET EOR 610(End of Record) 611sequence. 612.It Ic escape 613Sends the current 614.Nm telnet 615escape character (initially \*(Lq^\*(Rq). 616.It Ic ga 617Sends the 618.Dv TELNET GA 619(Go Ahead) 620sequence, which likely has no significance to the remote system. 621.It Ic getstatus 622If the remote side supports the 623.Dv TELNET STATUS 624command, 625.Ic getstatus 626will send the subnegotiation to request that the server send 627its current option status. 628.It Ic ip 629Sends the 630.Dv TELNET IP 631(Interrupt Process) sequence, which should cause the remote 632system to abort the currently running process. 633.It Ic nop 634Sends the 635.Dv TELNET NOP 636(No OPeration) 637sequence. 638.It Ic susp 639Sends the 640.Dv TELNET SUSP 641(SUSPend process) 642sequence. 643.It Ic synch 644Sends the 645.Dv TELNET SYNCH 646sequence. 647This sequence causes the remote system to discard all previously typed 648(but not yet read) input. 649This sequence is sent as 650.Tn TCP 651urgent 652data (and may not work if the remote system is a 653.Bx 4.2 654system -- if 655it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). 656.It Ic do Ar cmd 657.It Ic dont Ar cmd 658.It Ic will Ar cmd 659.It Ic wont Ar cmd 660Sends the 661.Dv TELNET DO 662.Ar cmd 663sequence. 664.Ar Cmd 665can be either a decimal number between 0 and 255, 666or a symbolic name for a specific 667.Dv TELNET 668command. 669.Ar Cmd 670can also be either 671.Ic help 672or 673.Ic \&? 674to print out help information, including 675a list of known symbolic names. 676.It Ic \&? 677Prints out help information for the 678.Ic send 679command. 680.El 681.It Ic set Ar argument value 682.It Ic unset Ar argument value 683The 684.Ic set 685command will set any one of a number of 686.Nm telnet 687variables to a specific value or to 688.Dv TRUE . 689The special value 690.Ic off 691turns off the function associated with 692the variable, this is equivalent to using the 693.Ic unset 694command. 695The 696.Ic unset 697command will disable or set to 698.Dv FALSE 699any of the specified functions. 700The values of variables may be interrogated with the 701.Ic display 702command. 703The variables which may be set or unset, but not toggled, are 704listed here. In addition, any of the variables for the 705.Ic toggle 706command may be explicitly set or unset using 707the 708.Ic set 709and 710.Ic unset 711commands. 712.Bl -tag -width escape 713.It Ic ayt 714If 715.Tn TELNET 716is in localchars mode, or 717.Dv LINEMODE 718is enabled, and the status character is typed, a 719.Dv TELNET AYT 720sequence (see 721.Ic send ayt 722preceding) is sent to the 723remote host. The initial value for the "Are You There" 724character is the terminal's status character. 725.It Ic echo 726This is the value (initially \*(Lq^E\*(Rq) which, when in 727\*(Lqline by line\*(Rq mode, toggles between doing local echoing 728of entered characters (for normal processing), and suppressing 729echoing of entered characters (for entering, say, a password). 730.It Ic eof 731If 732.Nm telnet 733is operating in 734.Dv LINEMODE 735or \*(Lqold line by line\*(Rq mode, entering this character 736as the first character on a line will cause this character to be 737sent to the remote system. 738The initial value of the eof character is taken to be the terminal's 739.Ic eof 740character. 741.It Ic erase 742If 743.Nm telnet 744is in 745.Ic localchars 746mode (see 747.Ic toggle 748.Ic localchars 749below), 750.Sy and 751if 752.Nm telnet 753is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 754character is typed, a 755.Dv TELNET EC 756sequence (see 757.Ic send 758.Ic ec 759above) 760is sent to the remote system. 761The initial value for the erase character is taken to be 762the terminal's 763.Ic erase 764character. 765.It Ic escape 766This is the 767.Nm telnet 768escape character (initially \*(Lq^[\*(Rq) which causes entry 769into 770.Nm telnet 771command mode (when connected to a remote system). 772.It Ic flushoutput 773If 774.Nm telnet 775is in 776.Ic localchars 777mode (see 778.Ic toggle 779.Ic localchars 780below) 781and the 782.Ic flushoutput 783character is typed, a 784.Dv TELNET AO 785sequence (see 786.Ic send 787.Ic ao 788above) 789is sent to the remote host. 790The initial value for the flush character is taken to be 791the terminal's 792.Ic flush 793character. 794.It Ic forw1 795.It Ic forw2 796If 797.Tn TELNET 798is operating in 799.Dv LINEMODE , 800these are the 801characters that, when typed, cause partial lines to be 802forwarded to the remote system. The initial value for 803the forwarding characters are taken from the terminal's 804eol and eol2 characters. 805.It Ic interrupt 806If 807.Nm telnet 808is in 809.Ic localchars 810mode (see 811.Ic toggle 812.Ic localchars 813below) 814and the 815.Ic interrupt 816character is typed, a 817.Dv TELNET IP 818sequence (see 819.Ic send 820.Ic ip 821above) 822is sent to the remote host. 823The initial value for the interrupt character is taken to be 824the terminal's 825.Ic intr 826character. 827.It Ic kill 828If 829.Nm telnet 830is in 831.Ic localchars 832mode (see 833.Ic toggle 834.Ic localchars 835below), 836.Ic and 837if 838.Nm telnet 839is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 840character is typed, a 841.Dv TELNET EL 842sequence (see 843.Ic send 844.Ic el 845above) 846is sent to the remote system. 847The initial value for the kill character is taken to be 848the terminal's 849.Ic kill 850character. 851.It Ic lnext 852If 853.Nm telnet 854is operating in 855.Dv LINEMODE 856or \*(Lqold line by line\*(Lq mode, then this character is taken to 857be the terminal's 858.Ic lnext 859character. 860The initial value for the lnext character is taken to be 861the terminal's 862.Ic lnext 863character. 864.It Ic quit 865If 866.Nm telnet 867is in 868.Ic localchars 869mode (see 870.Ic toggle 871.Ic localchars 872below) 873and the 874.Ic quit 875character is typed, a 876.Dv TELNET BRK 877sequence (see 878.Ic send 879.Ic brk 880above) 881is sent to the remote host. 882The initial value for the quit character is taken to be 883the terminal's 884.Ic quit 885character. 886.It Ic reprint 887If 888.Nm telnet 889is operating in 890.Dv LINEMODE 891or \*(Lqold line by line\*(Lq mode, then this character is taken to 892be the terminal's 893.Ic reprint 894character. 895The initial value for the reprint character is taken to be 896the terminal's 897.Ic reprint 898character. 899.It Ic rlogin 900This is the rlogin escape character. 901If set, the normal 902.Tn TELNET 903escape character is ignored unless it is 904preceded by this character at the beginning of a line. 905This character, at the beginning of a line followed by 906a "." closes the connection; when followed by a ^Z it 907suspends the telnet command. The initial state is to 908disable the rlogin escape character. 909.It Ic start 910If the 911.Dv TELNET TOGGLE-FLOW-CONTROL 912option has been enabled, 913then this character is taken to 914be the terminal's 915.Ic start 916character. 917The initial value for the kill character is taken to be 918the terminal's 919.Ic start 920character. 921.It Ic stop 922If the 923.Dv TELNET TOGGLE-FLOW-CONTROL 924option has been enabled, 925then this character is taken to 926be the terminal's 927.Ic stop 928character. 929The initial value for the kill character is taken to be 930the terminal's 931.Ic stop 932character. 933.It Ic susp 934If 935.Nm telnet 936is in 937.Ic localchars 938mode, or 939.Dv LINEMODE 940is enabled, and the 941.Ic suspend 942character is typed, a 943.Dv TELNET SUSP 944sequence (see 945.Ic send 946.Ic susp 947above) 948is sent to the remote host. 949The initial value for the suspend character is taken to be 950the terminal's 951.Ic suspend 952character. 953.It Ic tracefile 954This is the file to which the output, caused by 955.Ic netdata 956or 957.Ic option 958tracing being 959.Dv TRUE , 960will be written. If it is set to 961.Dq Fl , 962then tracing information will be written to standard output (the default). 963.It Ic worderase 964If 965.Nm telnet 966is operating in 967.Dv LINEMODE 968or \*(Lqold line by line\*(Lq mode, then this character is taken to 969be the terminal's 970.Ic worderase 971character. 972The initial value for the worderase character is taken to be 973the terminal's 974.Ic worderase 975character. 976.It Ic \&? 977Displays the legal 978.Ic set 979.Pq Ic unset 980commands. 981.El 982.It Ic slc Ar state 983The 984.Ic slc 985command (Set Local Characters) is used to set 986or change the state of the the special 987characters when the 988.Dv TELNET LINEMODE 989option has 990been enabled. Special characters are characters that get 991mapped to 992.Tn TELNET 993commands sequences (like 994.Ic ip 995or 996.Ic quit ) 997or line editing characters (like 998.Ic erase 999and 1000.Ic kill ) . 1001By default, the local special characters are exported. 1002.Bl -tag -width Fl 1003.It Ic check 1004Verify the current settings for the current special characters. 1005The remote side is requested to send all the current special 1006character settings, and if there are any discrepancies with 1007the local side, the local side will switch to the remote value. 1008.It Ic export 1009Switch to the local defaults for the special characters. The 1010local default characters are those of the local terminal at 1011the time when 1012.Nm telnet 1013was started. 1014.It Ic import 1015Switch to the remote defaults for the special characters. 1016The remote default characters are those of the remote system 1017at the time when the 1018.Tn TELNET 1019connection was established. 1020.It Ic \&? 1021Prints out help information for the 1022.Ic slc 1023command. 1024.El 1025.It Ic status 1026Show the current status of 1027.Nm telnet . 1028This includes the peer one is connected to, as well 1029as the current mode. 1030.It Ic toggle Ar arguments ... 1031Toggle (between 1032.Dv TRUE 1033and 1034.Dv FALSE ) 1035various flags that control how 1036.Nm telnet 1037responds to events. 1038These flags may be set explicitly to 1039.Dv TRUE 1040or 1041.Dv FALSE 1042using the 1043.Ic set 1044and 1045.Ic unset 1046commands listed above. 1047More than one argument may be specified. 1048The state of these flags may be interrogated with the 1049.Ic display 1050command. 1051Valid arguments are: 1052.Bl -tag -width Ar 1053.It Ic authdebug 1054Turns on debugging information for the authentication code. 1055.It Ic autoflush 1056If 1057.Ic autoflush 1058and 1059.Ic localchars 1060are both 1061.Dv TRUE , 1062then when the 1063.Ic ao , 1064or 1065.Ic quit 1066characters are recognized (and transformed into 1067.Tn TELNET 1068sequences; see 1069.Ic set 1070above for details), 1071.Nm telnet 1072refuses to display any data on the user's terminal 1073until the remote system acknowledges (via a 1074.Dv TELNET TIMING MARK 1075option) 1076that it has processed those 1077.Tn TELNET 1078sequences. 1079The initial value for this toggle is 1080.Dv TRUE 1081if the terminal user had not 1082done an "stty noflsh", otherwise 1083.Dv FALSE 1084(see 1085.Xr stty 1 ) . 1086.It Ic autodecrypt 1087When the 1088.Dv TELNET ENCRYPT 1089option is negotiated, by 1090default the actual encryption (decryption) of the data 1091stream does not start automatically. The autoencrypt 1092(autodecrypt) command states that encryption of the 1093output (input) stream should be enabled as soon as 1094possible. 1095.Pp 1096Note: Because of export controls, the 1097.Dv TELNET ENCRYPT 1098option is not supported outside the United States and Canada. 1099.It Ic autologin 1100If the remote side supports the 1101.Dv TELNET AUTHENTICATION 1102option 1103.Tn TELNET 1104attempts to use it to perform automatic authentication. If the 1105.Dv AUTHENTICATION 1106option is not supported, the user's login 1107name are propagated through the 1108.Dv TELNET ENVIRON 1109option. 1110This command is the same as specifying 1111.Ar a 1112option on the 1113.Ic open 1114command. 1115.It Ic autosynch 1116If 1117.Ic autosynch 1118and 1119.Ic localchars 1120are both 1121.Dv TRUE , 1122then when either the 1123.Ic intr 1124or 1125.Ic quit 1126characters is typed (see 1127.Ic set 1128above for descriptions of the 1129.Ic intr 1130and 1131.Ic quit 1132characters), the resulting 1133.Tn TELNET 1134sequence sent is followed by the 1135.Dv TELNET SYNCH 1136sequence. 1137This procedure 1138.Ic should 1139cause the remote system to begin throwing away all previously 1140typed input until both of the 1141.Tn TELNET 1142sequences have been read and acted upon. 1143The initial value of this toggle is 1144.Dv FALSE . 1145.It Ic binary 1146Enable or disable the 1147.Dv TELNET BINARY 1148option on both input and output. 1149.It Ic inbinary 1150Enable or disable the 1151.Dv TELNET BINARY 1152option on input. 1153.It Ic outbinary 1154Enable or disable the 1155.Dv TELNET BINARY 1156option on output. 1157.It Ic crlf 1158If this is 1159.Dv TRUE , 1160then carriage returns will be sent as 1161.Li <CR><LF> . 1162If this is 1163.Dv FALSE , 1164then carriage returns will be send as 1165.Li <CR><NUL> . 1166The initial value for this toggle is 1167.Dv FALSE . 1168.It Ic crmod 1169Toggle carriage return mode. 1170When this mode is enabled, most carriage return characters received from 1171the remote host will be mapped into a carriage return followed by 1172a line feed. 1173This mode does not affect those characters typed by the user, only 1174those received from the remote host. 1175This mode is not very useful unless the remote host 1176only sends carriage return, but never line feed. 1177The initial value for this toggle is 1178.Dv FALSE . 1179.It Ic debug 1180Toggles socket level debugging (useful only to the 1181.Ic super user ) . 1182The initial value for this toggle is 1183.Dv FALSE . 1184.It Ic encdebug 1185Turns on debugging information for the encryption code. 1186.It Ic localchars 1187If this is 1188.Dv TRUE , 1189then the 1190.Ic flush , 1191.Ic interrupt , 1192.Ic quit , 1193.Ic erase , 1194and 1195.Ic kill 1196characters (see 1197.Ic set 1198above) are recognized locally, and transformed into (hopefully) appropriate 1199.Tn TELNET 1200control sequences 1201(respectively 1202.Ic ao , 1203.Ic ip , 1204.Ic brk , 1205.Ic ec , 1206and 1207.Ic el ; 1208see 1209.Ic send 1210above). 1211The initial value for this toggle is 1212.Dv TRUE 1213in \*(Lqold line by line\*(Rq mode, 1214and 1215.Dv FALSE 1216in \*(Lqcharacter at a time\*(Rq mode. 1217When the 1218.Dv LINEMODE 1219option is enabled, the value of 1220.Ic localchars 1221is ignored, and assumed to always be 1222.Dv TRUE . 1223If 1224.Dv LINEMODE 1225has ever been enabled, then 1226.Ic quit 1227is sent as 1228.Ic abort , 1229and 1230.Ic eof and 1231.B suspend 1232are sent as 1233.Ic eof and 1234.Ic susp , 1235see 1236.Ic send 1237above). 1238.It Ic netdata 1239Toggles the display of all network data (in hexadecimal format). 1240The initial value for this toggle is 1241.Dv FALSE . 1242.It Ic options 1243Toggles the display of some internal 1244.Nm telnet 1245protocol processing (having to do with 1246.Tn TELNET 1247options). 1248The initial value for this toggle is 1249.Dv FALSE . 1250.It Ic prettydump 1251When the 1252.Ic netdata 1253toggle is enabled, if 1254.Ic prettydump 1255is enabled the output from the 1256.Ic netdata 1257command will be formatted in a more user readable format. 1258Spaces are put between each character in the output, and the 1259beginning of any 1260.Tn TELNET 1261escape sequence is preceded by a '*' to aid in locating them. 1262.It Ic skiprc 1263When the skiprc toggle is 1264.Dv TRUE , 1265.Tn TELNET 1266skips the reading of the 1267.Pa \&.telnetrc 1268file in the users home 1269directory when connections are opened. The initial 1270value for this toggle is 1271.Dv FALSE. 1272.It Ic termdata 1273Toggles the display of all terminal data (in hexadecimal format). 1274The initial value for this toggle is 1275.Dv FALSE . 1276.It Ic verbose_encrypt 1277When the 1278.Ic verbose_encrypt 1279toggle is 1280.Dv TRUE , 1281.Tn TELNET 1282prints out a message each time encryption is enabled or 1283disabled. The initial value for this toggle is 1284.Dv FALSE. 1285Note: Because of export controls, data encryption 1286is not supported outside of the United States and Canada. 1287.It Ic \&? 1288Displays the legal 1289.Ic toggle 1290commands. 1291.El 1292.It Ic z 1293Suspend 1294.Nm telnet . 1295This command only works when the user is using the 1296.Xr csh 1 . 1297.It Ic \&! Op Ar command 1298Execute a single command in a subshell on the local 1299system. If 1300.Ic command 1301is omitted, then an interactive 1302subshell is invoked. 1303.It Ic \&? Op Ar command 1304Get help. With no arguments, 1305.Nm telnet 1306prints a help summary. 1307If a command is specified, 1308.Nm telnet 1309will print the help information for just that command. 1310.El 1311.Sh ENVIRONMENT 1312.Nm Telnet 1313uses at least the 1314.Ev HOME , 1315.Ev SHELL , 1316.Ev DISPLAY , 1317and 1318.Ev TERM 1319environment variables. 1320Other environment variables may be propagated 1321to the other side via the 1322.Dv TELNET ENVIRON 1323option. 1324.Sh FILES 1325.Bl -tag -width ~/.telnetrc -compact 1326.It Pa ~/.telnetrc 1327user customized telnet startup values 1328.El 1329.Sh HISTORY 1330The 1331.Nm Telnet 1332command appeared in 1333.Bx 4.2 . 1334.Sh NOTES 1335.Pp 1336On some remote systems, echo has to be turned off manually when in 1337\*(Lqold line by line\*(Rq mode. 1338.Pp 1339In \*(Lqold line by line\*(Rq mode or 1340.Dv LINEMODE 1341the terminal's 1342.Ic eof 1343character is only recognized (and sent to the remote system) 1344when it is the first character on a line. 1345