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 8.3 (Berkeley) 01/05/94 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 d 19.Op Fl a 20.Op Fl n Ar tracefile 21.Op Fl e Ar escapechar 22.Oo 23.Op Fl l Ar user 24.Ar host 25.Op port 26.Oc 27.Sh DESCRIPTION 28The 29.Nm telnet 30command 31is used to communicate with another host using the 32.Tn TELNET 33protocol. 34If 35.Nm telnet 36is invoked without the 37.Ar host 38argument, it enters command mode, 39indicated by its prompt 40.Pq Nm telnet\&> . 41In this mode, it accepts and executes the commands listed below. 42If it is invoked with arguments, it performs an 43.Ic open 44command with those arguments. 45.Pp 46Options: 47.Bl -tag -width indent 48.It Fl d 49Sets the initial value of the 50.Ic debug 51toggle to 52.Dv TRUE 53.It Fl a 54Attempt automatic login. 55Currently, this sends the user name via the 56.Ev USER 57variable 58of the 59.Ev ENVIRON 60option if supported by the remote system. 61The name used is that of the current user as returned by 62.Xr getlogin 2 63if it agrees with the current user ID, 64otherwise it is the name associated with the user ID. 65.It Fl n Ar tracefile 66Opens 67.Ar tracefile 68for recording trace information. 69See the 70.Ic set tracefile 71command below. 72.It Fl l Ar user 73When connecting to the remote system, if the remote system 74understands the 75.Ev ENVIRON 76option, then 77.Ar user 78will be sent to the remote system as the value for the variable USER. 79This option implies the 80.Fl a 81option. 82This option may also be used with the 83.Ic open 84command. 85.It Fl e Ar escape char 86Sets the initial 87.Nm 88.Nm telnet 89escape character to 90.Ar escape char. 91If 92.Ar escape char 93is ommitted, then 94there will be no escape character. 95.It Fl E 96The 97.Fl E 98option stops any character from being recognized as an escape character. 99.It Ar host 100Indicates the official name, an alias, or the Internet address 101of a remote host. 102.It Ar port 103Indicates a port number (address of an application). If a number is 104not specified, the default 105.Nm telnet 106port is used. 107.El 108.Pp 109Once a connection has been opened, 110.Nm telnet 111will attempt to enable the 112.Dv TELNET LINEMODE 113option. 114If this fails, then 115.Nm telnet 116will revert to one of two input modes: 117either \*(Lqcharacter at a time\*(Rq 118or \*(Lqold line by line\*(Rq 119depending on what the remote system supports. 120.Pp 121When 122.Dv LINEMODE 123is enabled, character processing is done on the 124local system, under the control of the remote system. When input 125editing or character echoing is to be disabled, the remote system 126will relay that information. The remote system will also relay 127changes to any special characters that happen on the remote 128system, so that they can take effect on the local system. 129.Pp 130In \*(Lqcharacter at a time\*(Rq mode, most 131text typed is immediately sent to the remote host for processing. 132.Pp 133In \*(Lqold line by line\*(Rq mode, all text is echoed locally, 134and (normally) only completed lines are sent to the remote host. 135The \*(Lqlocal echo character\*(Rq (initially \*(Lq^E\*(Rq) may be used 136to turn off and on the local echo 137(this would mostly be used to enter passwords 138without the password being echoed). 139.Pp 140If the 141.Dv LINEMODE 142option is enabled, or if the 143.Ic localchars 144toggle is 145.Dv TRUE 146(the default for \*(Lqold line by line\*(Lq; see below), 147the user's 148.Ic quit , 149.Ic intr , 150and 151.Ic flush 152characters are trapped locally, and sent as 153.Tn TELNET 154protocol sequences to the remote side. 155If 156.Dv LINEMODE 157has ever been enabled, then the user's 158.Ic susp 159and 160.Ic eof 161are also sent as 162.Tn TELNET 163protocol sequences, 164and 165.Ic quit 166is sent as a 167.Dv TELNET ABORT 168instead of 169.Dv BREAK 170There are options (see 171.Ic toggle 172.Ic autoflush 173and 174.Ic toggle 175.Ic autosynch 176below) 177which cause this action to flush subsequent output to the terminal 178(until the remote host acknowledges the 179.Tn TELNET 180sequence) and flush previous terminal input 181(in the case of 182.Ic quit 183and 184.Ic intr ) . 185.Pp 186While connected to a remote host, 187.Nm telnet 188command mode may be entered by typing the 189.Nm telnet 190\*(Lqescape character\*(Rq (initially \*(Lq^]\*(Rq). 191When in command mode, the normal terminal editing conventions are available. 192.Pp 193The following 194.Nm telnet 195commands are available. 196Only enough of each command to uniquely identify it need be typed 197(this is also true for arguments to the 198.Ic mode , 199.Ic set , 200.Ic toggle , 201.Ic unset , 202.Ic slc , 203.Ic environ , 204and 205.Ic display 206commands). 207.Pp 208.Bl -tag -width "mode type" 209.It Ic close 210Close a 211.Tn TELNET 212session and return to command mode. 213.It Ic display Ar argument ... 214Displays all, or some, of the 215.Ic set 216and 217.Ic toggle 218values (see below). 219.It Ic mode Ar type 220.Ar Type 221is one of several options, depending on the state of the 222.Tn TELNET 223session. 224The remote host is asked for permission to go into the requested mode. 225If the remote host is capable of entering that mode, the requested 226mode will be entered. 227.Bl -tag -width Ar 228.It Ic character 229Disable the 230.Dv TELNET LINEMODE 231option, or, if the remote side does not understand the 232.Dv LINEMODE 233option, then enter \*(Lqcharacter at a time\*(Lq mode. 234.It Ic line 235Enable the 236.Dv TELNET LINEMODE 237option, or, if the remote side does not understand the 238.Dv LINEMODE 239option, then attempt to enter \*(Lqold-line-by-line\*(Lq mode. 240.It Ic isig Pq Ic \-isig 241Attempt to enable (disable) the 242.Dv TRAPSIG 243mode of the 244.Dv LINEMODE 245option. 246This requires that the 247.Dv LINEMODE 248option be enabled. 249.It Ic edit Pq Ic \-edit 250Attempt to enable (disable) the 251.Dv EDIT 252mode of the 253.Dv LINEMODE 254option. 255This requires that the 256.Dv LINEMODE 257option be enabled. 258.It Ic softtabs Pq Ic \-softtabs 259Attempt to enable (disable) the 260.Dv SOFT_TAB 261mode of the 262.Dv LINEMODE 263option. 264This requires that the 265.Dv LINEMODE 266option be enabled. 267.It Ic litecho Pq Ic \-litecho 268Attempt to enable (disable) the 269.Dv LIT_ECHO 270mode of the 271.Dv LINEMODE 272option. 273This requires that the 274.Dv LINEMODE 275option be enabled. 276.It Ic \&? 277Prints out help information for the 278.Ic mode 279command. 280.El 281.It Xo 282.Ic open Ar host 283.Oo Op Fl l 284.Ar user 285.Oc Ns Oo Fl 286.Ar port Oc 287.Xc 288Open a connection to the named host. 289If no port number 290is specified, 291.Nm telnet 292will attempt to contact a 293.Tn TELNET 294server at the default port. 295The host specification may be either a host name (see 296.Xr hosts 5 ) 297or an Internet address specified in the \*(Lqdot notation\*(Rq (see 298.Xr inet 3 ) . 299The 300.Op Fl l 301option may be used to specify the user name 302to be passed to the remote system via the 303.Ev ENVIRON 304option. 305When connecting to a non-standard port, 306.Nm telnet 307omits any automatic initiation of 308.Tn TELNET 309options. When the port number is preceeded by a minus sign, 310the inital option negotiation is done. 311After establishing a connection, the file 312.Pa \&.telnetrc 313in the 314users home directory is opened. Lines begining with a # are 315comment lines. Blank lines are ignored. Lines that begin 316without whitespace are the start of a machine entry. The 317first thing on the line is the name of the machine that is 318being connected to. The rest of the line, and successive 319lines that begin with whitespace are assumed to be 320.Nm telnet 321commands and are processed as if they had been typed 322in manually to the 323.Nm telnet 324command prompt. 325.It Ic quit 326Close any open 327.Tn TELNET 328session and exit 329.Nm telnet . 330An end of file (in command mode) will also close a session and exit. 331.It Ic send Ar arguments 332Sends one or more special character sequences to the remote host. 333The following are the arguments which may be specified 334(more than one argument may be specified at a time): 335.Pp 336.Bl -tag -width escape 337.It Ic abort 338Sends the 339.Dv TELNET ABORT 340(Abort 341processes) 342sequence. 343.It Ic ao 344Sends the 345.Dv TELNET AO 346(Abort Output) sequence, which should cause the remote system to flush 347all output 348.Em from 349the remote system 350.Em to 351the user's terminal. 352.It Ic ayt 353Sends the 354.Dv TELNET AYT 355(Are You There) 356sequence, to which the remote system may or may not choose to respond. 357.It Ic brk 358Sends the 359.Dv TELNET BRK 360(Break) sequence, which may have significance to the remote 361system. 362.It Ic ec 363Sends the 364.Dv TELNET EC 365(Erase Character) 366sequence, which should cause the remote system to erase the last character 367entered. 368.It Ic el 369Sends the 370.Dv TELNET EL 371(Erase Line) 372sequence, which should cause the remote system to erase the line currently 373being entered. 374.It Ic eof 375Sends the 376.Dv TELNET EOF 377(End Of File) 378sequence. 379.It Ic eor 380Sends the 381.Dv TELNET EOR 382(End of Record) 383sequence. 384.It Ic escape 385Sends the current 386.Nm telnet 387escape character (initially \*(Lq^\*(Rq). 388.It Ic ga 389Sends the 390.Dv TELNET GA 391(Go Ahead) 392sequence, which likely has no significance to the remote system. 393.It Ic getstatus 394If the remote side supports the 395.Dv TELNET STATUS 396command, 397.Ic getstatus 398will send the subnegotiation to request that the server send 399its current option status. 400.It Ic ip 401Sends the 402.Dv TELNET IP 403(Interrupt Process) sequence, which should cause the remote 404system to abort the currently running process. 405.It Ic nop 406Sends the 407.Dv TELNET NOP 408(No OPeration) 409sequence. 410.It Ic susp 411Sends the 412.Dv TELNET SUSP 413(SUSPend process) 414sequence. 415.It Ic synch 416Sends the 417.Dv TELNET SYNCH 418sequence. 419This sequence causes the remote system to discard all previously typed 420(but not yet read) input. 421This sequence is sent as 422.Tn TCP 423urgent 424data (and may not work if the remote system is a 425.Bx 4.2 426system -- if 427it doesn't work, a lower case \*(Lqr\*(Rq may be echoed on the terminal). 428.It Ic \&? 429Prints out help information for the 430.Ic send 431command. 432.El 433.It Ic set Ar argument value 434.It Ic unset Ar argument value 435The 436.Ic set 437command will set any one of a number of 438.Nm telnet 439variables to a specific value or to 440.Dv TRUE . 441The special value 442.Ic off 443turns off the function associated with 444the variable, this is equivalent to using the 445.Ic unset 446command. 447The 448.Ic unset 449command will disable or set to 450.Dv FALSE 451any of the specified functions. 452The values of variables may be interrogated with the 453.Ic display 454command. 455The variables which may be set or unset, but not toggled, are 456listed here. In addition, any of the variables for the 457.Ic toggle 458command may be explicitly set or unset using 459the 460.Ic set 461and 462.Ic unset 463commands. 464.Bl -tag -width escape 465.It Ic echo 466This is the value (initially \*(Lq^E\*(Rq) which, when in 467\*(Lqline by line\*(Rq mode, toggles between doing local echoing 468of entered characters (for normal processing), and suppressing 469echoing of entered characters (for entering, say, a password). 470.It Ic eof 471If 472.Nm telnet 473is operating in 474.Dv LINEMODE 475or \*(Lqold line by line\*(Rq mode, entering this character 476as the first character on a line will cause this character to be 477sent to the remote system. 478The initial value of the eof character is taken to be the terminal's 479.Ic eof 480character. 481.It Ic erase 482If 483.Nm telnet 484is in 485.Ic localchars 486mode (see 487.Ic toggle 488.Ic localchars 489below), 490.Sy and 491if 492.Nm telnet 493is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 494character is typed, a 495.Dv TELNET EC 496sequence (see 497.Ic send 498.Ic ec 499above) 500is sent to the remote system. 501The initial value for the erase character is taken to be 502the terminal's 503.Ic erase 504character. 505.It Ic escape 506This is the 507.Nm telnet 508escape character (initially \*(Lq^[\*(Rq) which causes entry 509into 510.Nm telnet 511command mode (when connected to a remote system). 512.It Ic flushoutput 513If 514.Nm telnet 515is in 516.Ic localchars 517mode (see 518.Ic toggle 519.Ic localchars 520below) 521and the 522.Ic flushoutput 523character is typed, a 524.Dv TELNET AO 525sequence (see 526.Ic send 527.Ic ao 528above) 529is sent to the remote host. 530The initial value for the flush character is taken to be 531the terminal's 532.Ic flush 533character. 534.It Ic interrupt 535If 536.Nm telnet 537is in 538.Ic localchars 539mode (see 540.Ic toggle 541.Ic localchars 542below) 543and the 544.Ic interrupt 545character is typed, a 546.Dv TELNET IP 547sequence (see 548.Ic send 549.Ic ip 550above) 551is sent to the remote host. 552The initial value for the interrupt character is taken to be 553the terminal's 554.Ic intr 555character. 556.It Ic kill 557If 558.Nm telnet 559is in 560.Ic localchars 561mode (see 562.Ic toggle 563.Ic localchars 564below), 565.Ic and 566if 567.Nm telnet 568is operating in \*(Lqcharacter at a time\*(Rq mode, then when this 569character is typed, a 570.Dv TELNET EL 571sequence (see 572.Ic send 573.Ic el 574above) 575is sent to the remote system. 576The initial value for the kill character is taken to be 577the terminal's 578.Ic kill 579character. 580.It Ic lnext 581If 582.Nm telnet 583is operating in 584.Dv LINEMODE 585or \*(Lqold line by line\*(Lq mode, then this character is taken to 586be the terminal's 587.Ic lnext 588character. 589The initial value for the lnext character is taken to be 590the terminal's 591.Ic lnext 592character. 593.It Ic quit 594If 595.Nm telnet 596is in 597.Ic localchars 598mode (see 599.Ic toggle 600.Ic localchars 601below) 602and the 603.Ic quit 604character is typed, a 605.Dv TELNET BRK 606sequence (see 607.Ic send 608.Ic brk 609above) 610is sent to the remote host. 611The initial value for the quit character is taken to be 612the terminal's 613.Ic quit 614character. 615.It Ic reprint 616If 617.Nm telnet 618is operating in 619.Dv LINEMODE 620or \*(Lqold line by line\*(Lq mode, then this character is taken to 621be the terminal's 622.Ic reprint 623character. 624The initial value for the reprint character is taken to be 625the terminal's 626.Ic reprint 627character. 628.It Ic start 629If the 630.Dv TELNET TOGGLE-FLOW-CONTROL 631option has been enabled, 632then this character is taken to 633be the terminal's 634.Ic start 635character. 636The initial value for the kill character is taken to be 637the terminal's 638.Ic start 639character. 640.It Ic stop 641If the 642.Dv TELNET TOGGLE-FLOW-CONTROL 643option has been enabled, 644then this character is taken to 645be the terminal's 646.Ic stop 647character. 648The initial value for the kill character is taken to be 649the terminal's 650.Ic stop 651character. 652.It Ic susp 653If 654.Nm telnet 655is in 656.Ic localchars 657mode, or 658.Dv LINEMODE 659is enabled, and the 660.Ic suspend 661character is typed, a 662.Dv TELNET SUSP 663sequence (see 664.Ic send 665.Ic susp 666above) 667is sent to the remote host. 668The initial value for the suspend character is taken to be 669the terminal's 670.Ic suspend 671character. 672.It Ic tracefile 673This is the file to which the output, caused by 674.Ic netdata 675or 676.Ic option 677tracing being 678.Dv TRUE , 679will be written. If it is set to 680.Dq Fl , 681then tracing information will be written to standard output (the default). 682.It Ic worderase 683If 684.Nm telnet 685is operating in 686.Dv LINEMODE 687or \*(Lqold line by line\*(Lq mode, then this character is taken to 688be the terminal's 689.Ic worderase 690character. 691The initial value for the worderase character is taken to be 692the terminal's 693.Ic worderase 694character. 695.It Ic \&? 696Displays the legal 697.Ic set 698.Pq Ic unset 699commands. 700.El 701.It Ic slc Ar state 702The 703.Ic slc 704command (Set Local Characters) is used to set 705or change the state of the special 706characters when the 707.Dv TELNET LINEMODE 708option has 709been enabled. Special characters are characters that get 710mapped to 711.Tn TELNET 712commands sequences (like 713.Ic ip 714or 715.Ic quit ) 716or line editing characters (like 717.Ic erase 718and 719.Ic kill ) . 720By default, the local special characters are exported. 721.Bl -tag -width Fl 722.It Ic export 723Switch to the local defaults for the special characters. The 724local default characters are those of the local terminal at 725the time when 726.Nm telnet 727was started. 728.It Ic import 729Switch to the remote defaults for the special characters. 730The remote default characters are those of the remote system 731at the time when the 732.Tn TELNET 733connection was established. 734.It Ic check 735Verify the current settings for the current special characters. 736The remote side is requested to send all the current special 737character settings, and if there are any discrepancies with 738the local side, the local side will switch to the remote value. 739.It Ic \&? 740Prints out help information for the 741.Ic slc 742command. 743.El 744.It Ic environ Ar arguments... 745The 746.Ic environ 747command is used to manipulate 748the variables that may be sent through the 749.Dv TELNET ENVIRON 750option. 751The initial set of variables is taken from the user's 752environment, with only the 753.Ev DISPLAY 754and 755.Ev PRINTER 756variables being exported by default. 757The 758.Ev USER 759variable is also exported if the 760.Fl a 761or 762.Fl l 763options are used. 764.br 765Valid arguments for the 766.Ic environ 767command are: 768.Bl -tag -width Fl 769.It Ic define Ar variable value 770Define the variable 771.Ar variable 772to have a value of 773.Ar value. 774Any variables defined by this command are automatically exported. 775The 776.Ar value 777may be enclosed in single or double quotes so 778that tabs and spaces may be included. 779.It Ic undefine Ar variable 780Remove 781.Ar variable 782from the list of environment variables. 783.It Ic export Ar variable 784Mark the variable 785.Ar variable 786to be exported to the remote side. 787.It Ic unexport Ar variable 788Mark the variable 789.Ar variable 790to not be exported unless 791explicitly asked for by the remote side. 792.It Ic list 793List the current set of environment variables. 794Those marked with a 795.Cm * 796will be sent automatically, 797other variables will only be sent if explicitly requested. 798.It Ic \&? 799Prints out help information for the 800.Ic environ 801command. 802.El 803.It Ic toggle Ar arguments ... 804Toggle (between 805.Dv TRUE 806and 807.Dv FALSE ) 808various flags that control how 809.Nm telnet 810responds to events. 811These flags may be set explicitly to 812.Dv TRUE 813or 814.Dv FALSE 815using the 816.Ic set 817and 818.Ic unset 819commands listed above. 820More than one argument may be specified. 821The state of these flags may be interrogated with the 822.Ic display 823command. 824Valid arguments are: 825.Bl -tag -width Ar 826.It Ic autoflush 827If 828.Ic autoflush 829and 830.Ic localchars 831are both 832.Dv TRUE , 833then when the 834.Ic ao , 835or 836.Ic quit 837characters are recognized (and transformed into 838.Tn TELNET 839sequences; see 840.Ic set 841above for details), 842.Nm telnet 843refuses to display any data on the user's terminal 844until the remote system acknowledges (via a 845.Dv TELNET TIMING MARK 846option) 847that it has processed those 848.Tn TELNET 849sequences. 850The initial value for this toggle is 851.Dv TRUE 852if the terminal user had not 853done an "stty noflsh", otherwise 854.Dv FALSE 855(see 856.Xr stty 1 ) . 857.It Ic autosynch 858If 859.Ic autosynch 860and 861.Ic localchars 862are both 863.Dv TRUE , 864then when either the 865.Ic intr 866or 867.Ic quit 868characters is typed (see 869.Ic set 870above for descriptions of the 871.Ic intr 872and 873.Ic quit 874characters), the resulting 875.Tn TELNET 876sequence sent is followed by the 877.Dv TELNET SYNCH 878sequence. 879This procedure 880.Ic should 881cause the remote system to begin throwing away all previously 882typed input until both of the 883.Tn TELNET 884sequences have been read and acted upon. 885The initial value of this toggle is 886.Dv FALSE . 887.It Ic binary 888Enable or disable the 889.Dv TELNET BINARY 890option on both input and output. 891.It Ic inbinary 892Enable or disable the 893.Dv TELNET BINARY 894option on input. 895.It Ic outbinary 896Enable or disable the 897.Dv TELNET BINARY 898option on output. 899.It Ic crlf 900If this is 901.Dv TRUE , 902then carriage returns will be sent as 903.Li <CR><LF> . 904If this is 905.Dv FALSE , 906then carriage returns will be send as 907.Li <CR><NUL> . 908The initial value for this toggle is 909.Dv FALSE . 910.It Ic crmod 911Toggle carriage return mode. 912When this mode is enabled, most carriage return characters received from 913the remote host will be mapped into a carriage return followed by 914a line feed. 915This mode does not affect those characters typed by the user, only 916those received from the remote host. 917This mode is not very useful unless the remote host 918only sends carriage return, but never line feed. 919The initial value for this toggle is 920.Dv FALSE . 921.It Ic debug 922Toggles socket level debugging (useful only to the 923.Ic super user ) . 924The initial value for this toggle is 925.Dv FALSE . 926.It Ic localchars 927If this is 928.Dv TRUE , 929then the 930.Ic flush , 931.Ic interrupt , 932.Ic quit , 933.Ic erase , 934and 935.Ic kill 936characters (see 937.Ic set 938above) are recognized locally, and transformed into (hopefully) appropriate 939.Tn TELNET 940control sequences 941(respectively 942.Ic ao , 943.Ic ip , 944.Ic brk , 945.Ic ec , 946and 947.Ic el ; 948see 949.Ic send 950above). 951The initial value for this toggle is 952.Dv TRUE 953in \*(Lqold line by line\*(Rq mode, 954and 955.Dv FALSE 956in \*(Lqcharacter at a time\*(Rq mode. 957When the 958.Dv LINEMODE 959option is enabled, the value of 960.Ic localchars 961is ignored, and assumed to always be 962.Dv TRUE . 963If 964.Dv LINEMODE 965has ever been enabled, then 966.Ic quit 967is sent as 968.Ic abort , 969and 970.Ic eof and 971.B suspend 972are sent as 973.Ic eof and 974.Ic susp , 975see 976.Ic send 977above). 978.It Ic netdata 979Toggles the display of all network data (in hexadecimal format). 980The initial value for this toggle is 981.Dv FALSE . 982.It Ic options 983Toggles the display of some internal 984.Nm telnet 985protocol processing (having to do with 986.Tn TELNET 987options). 988The initial value for this toggle is 989.Dv FALSE . 990.It Ic prettydump 991When the 992.Ic netdata 993toggle is enabled, if 994.Ic prettydump 995is enabled the output from the 996.Ic netdata 997command will be formated in a more user readable format. 998Spaces are put between each character in the output, and the 999begining of any 1000.Tn TELNET 1001escape sequence is preceeded by a '*' to aid in locating them. 1002.It Ic \&? 1003Displays the legal 1004.Ic toggle 1005commands. 1006.El 1007.It Ic z 1008Suspend 1009.Nm telnet . 1010This command only works when the user is using the 1011.Xr csh 1 . 1012.It Ic \&! Op Ar command 1013Execute a single command in a subshell on the local 1014system. If 1015.Ic command 1016is ommitted, then an interactive 1017subshell is invoked. 1018.It Ic status 1019Show the current status of 1020.Nm telnet . 1021This includes the peer one is connected to, as well 1022as the current mode. 1023.It Ic \&? Op Ar command 1024Get help. With no arguments, 1025.Nm telnet 1026prints a help summary. 1027If a command is specified, 1028.Nm telnet 1029will print the help information for just that command. 1030.El 1031.Sh ENVIRONMENT 1032.Nm Telnet 1033uses at least the 1034.Ev HOME , 1035.Ev SHELL , 1036.Ev DISPLAY , 1037and 1038.Ev TERM 1039environment variables. 1040Other environment variables may be propagated 1041to the other side via the 1042.Dv TELNET ENVIRON 1043option. 1044.Sh FILES 1045.Bl -tag -width ~/.telnetrc -compact 1046.It Pa ~/.telnetrc 1047user customized telnet startup values 1048.El 1049.Sh HISTORY 1050The 1051.Nm Telnet 1052command appeared in 1053.Bx 4.2 . 1054.Sh NOTES 1055.Pp 1056On some remote systems, echo has to be turned off manually when in 1057\*(Lqold line by line\*(Rq mode. 1058.Pp 1059In \*(Lqold line by line\*(Rq mode or 1060.Dv LINEMODE 1061the terminal's 1062.Ic eof 1063character is only recognized (and sent to the remote system) 1064when it is the first character on a line. 1065