man4/console_codes.4

   1 '\" t
   2 .\" Copyright (c) 1996 Andries Brouwer <aeb@cwi.nl>, Mon Oct 31 22:13:04 1996
   3 .\"
   4 .\" %%%LICENSE_START(GPLv2+_DOC_ONEPARA)
   5 .\" This is free documentation; you can redistribute it and/or
   6 .\" modify it under the terms of the GNU General Public License as
   7 .\" published by the Free Software Foundation; either version 2 of
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   9 .\" %%%LICENSE_END
  10 .\"
  11 .\" This is combined from many sources.
  12 .\" For Linux, the definitive source is of course console.c.
  13 .\" About vt100-like escape sequences in general there are
  14 .\" the ISO 6429 and ISO 2022 norms, the descriptions of
  15 .\" an actual vt100, and the xterm docs (ctlseqs.ms).
  16 .\" Substantial portions of this text are derived from a write-up
  17 .\" by Eric S. Raymond <esr@thyrsus.com>.
  18 .\"
  19 .\" Tiny correction, aeb, 961107.
  20 .\"
  21 .\" 2006-05-27, Several corrections - Thomas E. Dickey
  22 .\"
  23 .TH CONSOLE_CODES 4 2019-03-06 "Linux" "Linux Programmer's Manual"
  24 .SH NAME
  25 console_codes \- Linux console escape and control sequences
  26 .SH DESCRIPTION
  27 The Linux console implements a large subset of the VT102 and ECMA-48/ISO
  28 6429/ANSI X3.64 terminal controls, plus certain private-mode sequences
  29 for changing the color palette, character-set mapping, and so on.
  30 In the tabular descriptions below, the second column gives ECMA-48 or DEC
  31 mnemonics (the latter if prefixed with DEC) for the given function.
  32 Sequences without a mnemonic are neither ECMA-48 nor VT102.
  33 .PP
  34 After all the normal output processing has been done, and a
  35 stream of characters arrives at the console driver for actual
  36 printing, the first thing that happens is a translation from
  37 the code used for processing to the code used for printing.
  38 .PP
  39 If the console is in UTF-8 mode, then the incoming bytes are
  40 first assembled into 16-bit Unicode codes.
  41 Otherwise, each byte is transformed according to the current mapping table
  42 (which translates it to a Unicode value).
  43 See the \fBCharacter Sets\fP section below for discussion.
  44 .PP
  45 In the normal case, the Unicode value is converted to a font index,
  46 and this is stored in video memory, so that the corresponding glyph
  47 (as found in video ROM) appears on the screen.
  48 Note that the use of Unicode (and the design of the PC hardware)
  49 allows us to use 512 different glyphs simultaneously.
  50 .PP
  51 If the current Unicode value is a control character, or we are
  52 currently processing an escape sequence, the value will treated
  53 specially.
  54 Instead of being turned into a font index and rendered as
  55 a glyph, it may trigger cursor movement or other control functions.
  56 See the \fBLinux Console Controls\fP section below for discussion.
  57 .PP
  58 It is generally not good practice to hard-wire terminal controls into
  59 programs.
  60 Linux supports a
  61 .BR terminfo (5)
  62 database of terminal capabilities.
  63 Rather than emitting console escape sequences by hand, you will almost
  64 always want to use a terminfo-aware screen library or utility such as
  65 .BR ncurses (3),
  66 .BR tput (1),
  67 or
  68 .BR reset (1).
  69 .SS Linux console controls
  70 This section describes all the control characters and escape sequences
  71 that invoke special functions (i.e., anything other than writing a
  72 glyph at the current cursor location) on the Linux console.
  73 .PP
  74 .B "Control characters"
  75 .PP
  76 A character is a control character if (before transformation
  77 according to the mapping table) it has one of the 14 codes
  78 00 (NUL), 07 (BEL), 08 (BS), 09 (HT), 0a (LF), 0b (VT),
  79 0c (FF), 0d (CR), 0e (SO), 0f (SI), 18 (CAN), 1a (SUB),
  80 1b (ESC), 7f (DEL).
  81 One can set a "display control characters" mode (see below),
  82 and allow 07, 09, 0b, 18, 1a, 7f to be displayed as glyphs.
  83 On the other hand, in UTF-8 mode all codes 00\(en1f are regarded
  84 as control characters, regardless of any "display control characters"
  85 mode.
  86 .PP
  87 If we have a control character, it is acted upon immediately
  88 and then discarded (even in the middle of an escape sequence)
  89 and the escape sequence continues with the next character.
  90 (However, ESC starts a new escape sequence, possibly aborting a previous
  91 unfinished one, and CAN and SUB abort any escape sequence.)
  92 The recognized control characters are BEL, BS, HT, LF, VT, FF,
  93 CR, SO, SI, CAN, SUB, ESC, DEL, CSI.
  94 They do what one would expect:
  95 .HP
  96 BEL (0x07, \fB^G\fP) beeps;
  97 .HP
  98 BS (0x08, \fB^H\fP) backspaces one column
  99 (but not past the beginning of the line);
 100 .HP
 101 HT (0x09, \fB^I\fP) goes to the next tab stop or to the end of the line
 102 if there is no earlier tab stop;
 103 .HP
 104 LF (0x0A, \fB^J\fP), VT (0x0B, \fB^K\fP) and
 105 FF (0x0C, \fB^L\fP) all give a linefeed,
 106 and if LF/NL (new-line mode) is set also a carriage return;
 107 .HP
 108 CR (0x0D, \fB^M\fP) gives a carriage return;
 109 .HP
 110 SO (0x0E, \fB^N\fP) activates the G1 character set;
 111 .HP
 112 SI (0x0F, \fB^O\fP) activates the G0 character set;
 113 .HP
 114 CAN (0x18, \fB^X\fP) and SUB (0x1A, \fB^Z\fP) interrupt escape sequences;
 115 .HP
 116 ESC (0x1B, \fB^[\fP) starts an escape sequence;
 117 .HP
 118 DEL (0x7F) is ignored;
 119 .HP
 120 CSI (0x9B) is equivalent to ESC [.
 121 .PP
 122 .B "ESC- but not CSI-sequences"
 123 .TS
 124 l l l.
 125 ESC c   RIS     Reset.
 126 ESC D   IND     Linefeed.
 127 ESC E   NEL     Newline.
 128 ESC H   HTS     Set tab stop at current column.
 129 ESC M   RI      Reverse linefeed.
 130 ESC Z   DECID   T{
 131 DEC private identification. The kernel
 132 returns the string  ESC [ ? 6 c, claiming
 133 that it is a VT102.
 134 T}
 135 ESC 7   DECSC   T{
 136 Save current state (cursor coordinates,
 137 attributes, character sets pointed at by G0, G1).
 138 T}
 139 ESC 8   DECRC   Restore state most recently saved by ESC 7.
 140 ESC [   CSI     Control sequence introducer
 141 ESC %           Start sequence selecting character set
 142 ESC % @         \0\0\0Select default (ISO 646 / ISO 8859-1)
 143 ESC % G         \0\0\0Select UTF-8
 144 ESC % 8         \0\0\0Select UTF-8 (obsolete)
 145 ESC # 8 DECALN  DEC screen alignment test \- fill screen with E's.
 146 ESC (           Start sequence defining G0 character set
 147 ESC ( B         \0\0\0Select default (ISO 8859-1 mapping)
 148 ESC ( 0         \0\0\0Select VT100 graphics mapping
 149 ESC ( U         \0\0\0Select null mapping \- straight to character ROM
 150 ESC ( K         \0\0\0Select user mapping \- the map that is loaded by
 151                 \0\0\0the utility \fBmapscrn\fP(8).
 152 ESC )           Start sequence defining G1
 153                 (followed by one of B, 0, U, K, as above).
 154 ESC >   DECPNM  Set numeric keypad mode
 155 ESC =   DECPAM  Set application keypad mode
 156 ESC ]   OSC     T{
 157 (Should be: Operating system command)
 158 ESC ] P \fInrrggbb\fP: set palette, with parameter
 159 given in 7 hexadecimal digits after the final P :-(.
 160 Here \fIn\fP is the color (0\(en15), and \fIrrggbb\fP indicates
 161 the red/green/blue values (0\(en255).
 162 ESC ] R: reset palette
 163 T}
 164 .TE
 165 .PP
 166 .B "ECMA-48 CSI sequences"
 167 .PP
 168 CSI (or ESC [) is followed by a sequence of parameters,
 169 at most NPAR (16), that are decimal numbers separated by
 170 semicolons.
 171 An empty or absent parameter is taken to be 0.
 172 The sequence of parameters may be preceded by a single question mark.
 173 .PP
 174 However, after CSI [ (or ESC [ [) a single character is read
 175 and this entire sequence is ignored.
 176 (The idea is to ignore an echoed function key.)
 177 .PP
 178 The action of a CSI sequence is determined by its final character.
 179 .TS
 180 l l l.
 181 @       ICH     Insert the indicated # of blank characters.
 182 A       CUU     Move cursor up the indicated # of rows.
 183 B       CUD     Move cursor down the indicated # of rows.
 184 C       CUF     Move cursor right the indicated # of columns.
 185 D       CUB     Move cursor left the indicated # of columns.
 186 E       CNL     Move cursor down the indicated # of rows, to column 1.
 187 F       CPL     Move cursor up the indicated # of rows, to column 1.
 188 G       CHA     Move cursor to indicated column in current row.
 189 H       CUP     Move cursor to the indicated row, column (origin at 1,1).
 190 J       ED      Erase display (default: from cursor to end of display).
 191                 ESC [ 1 J: erase from start to cursor.
 192                 ESC [ 2 J: erase whole display.
 193                 ESC [ 3 J: erase whole display including scroll-back
 194                            buffer (since Linux 3.0).
 195 .\" ESC [ 3 J: commit f8df13e0a901fe55631fed66562369b4dba40f8b
 196 K       EL      Erase line (default: from cursor to end of line).
 197                 ESC [ 1 K: erase from start of line to cursor.
 198                 ESC [ 2 K: erase whole line.
 199 L       IL      Insert the indicated # of blank lines.
 200 M       DL      Delete the indicated # of lines.
 201 P       DCH     Delete the indicated # of characters on current line.
 202 X       ECH     Erase the indicated # of characters on current line.
 203 a       HPR     Move cursor right the indicated # of columns.
 204 c       DA      Answer ESC [ ? 6 c: "I am a VT102".
 205 d       VPA     Move cursor to the indicated row, current column.
 206 e       VPR     Move cursor down the indicated # of rows.
 207 f       HVP     Move cursor to the indicated row, column.
 208 g       TBC     Without parameter: clear tab stop at current position.
 209                 ESC [ 3 g: delete all tab stops.
 210 h       SM      Set Mode (see below).
 211 l       RM      Reset Mode (see below).
 212 m       SGR     Set attributes (see below).
 213 n       DSR     Status report (see below).
 214 q       DECLL   Set keyboard LEDs.
 215                 ESC [ 0 q: clear all LEDs
 216                 ESC [ 1 q: set Scroll Lock LED
 217                 ESC [ 2 q: set Num Lock LED
 218                 ESC [ 3 q: set Caps Lock LED
 219 r       DECSTBM Set scrolling region; parameters are top and bottom row.
 220 s       ?       Save cursor location.
 221 u       ?       Restore cursor location.
 222 \`      HPA     Move cursor to indicated column in current row.
 223 .TE
 224 .PP
 225 .B ECMA-48 Set Graphics Rendition
 226 .PP
 227 The ECMA-48 SGR sequence ESC [ \fIparameters\fP m sets display
 228 attributes.
 229 Several attributes can be set in the same sequence, separated by
 230 semicolons.
 231 An empty parameter (between semicolons or string initiator or
 232 terminator) is interpreted as a zero.
 233 .TS
 234 l l.
 235 param   result
 236 0       reset all attributes to their defaults
 237 1       set bold
 238 2       set half-bright (simulated with color on a color display)
 239 4       T{
 240 set underscore (simulated with color on a color display)
 241 (the colors used to simulate dim or underline are set
 242 using ESC ] ...)
 243 T}
 244 5       set blink
 245 7       set reverse video
 246 10      T{
 247 reset selected mapping, display control flag,
 248 and toggle meta flag (ECMA-48 says "primary font").
 249 T}
 250 11      T{
 251 select null mapping, set display control flag,
 252 reset toggle meta flag (ECMA-48 says "first alternate font").
 253 T}
 254 12      T{
 255 select null mapping, set display control flag,
 256 set toggle meta flag (ECMA-48 says "second alternate font").
 257 The toggle meta flag
 258 causes the high bit of a byte to be toggled
 259 before the mapping table translation is done.
 260 T}
 261 21      set normal intensity (ECMA-48 says "doubly underlined")
 262 22      set normal intensity
 263 24      underline off
 264 25      blink off
 265 27      reverse video off
 266 30      set black foreground
 267 31      set red foreground
 268 32      set green foreground
 269 33      set brown foreground
 270 34      set blue foreground
 271 35      set magenta foreground
 272 36      set cyan foreground
 273 37      set white foreground
 274 38      set underscore on, set default foreground color
 275 39      set underscore off, set default foreground color
 276 40      set black background
 277 41      set red background
 278 42      set green background
 279 43      set brown background
 280 44      set blue background
 281 45      set magenta background
 282 46      set cyan background
 283 47      set white background
 284 49      set default background color
 285 .TE
 286 .PP
 287 .B ECMA-48 Mode Switches
 288 .TP
 289 ESC [ 3 h
 290 DECCRM (default off): Display control chars.
 291 .TP
 292 ESC [ 4 h
 293 DECIM (default off): Set insert mode.
 294 .TP
 295 ESC [ 20 h
 296 LF/NL (default off): Automatically follow echo of LF, VT or FF with CR.
 297 .\"
 298 .PP
 299 .B ECMA-48 Status Report Commands
 300 .\"
 301 .TP
 302 ESC [ 5 n
 303 Device status report (DSR): Answer is ESC [ 0 n (Terminal OK).
 304 .TP
 305 ESC [ 6 n
 306 Cursor position report (CPR): Answer is ESC [ \fIy\fP ; \fIx\fP R,
 307 where \fIx,y\fP is the cursor location.
 308 .\"
 309 .PP
 310 .B DEC Private Mode (DECSET/DECRST) sequences
 311 .PP
 312 .\"
 313 These are not described in ECMA-48.
 314 We list the Set Mode sequences;
 315 the Reset Mode sequences are obtained by replacing the final \(aqh\(aq
 316 by \(aql\(aq.
 317 .TP
 318 ESC [ ? 1 h
 319 DECCKM (default off): When set, the cursor keys send an ESC O prefix,
 320 rather than ESC [.
 321 .TP
 322 ESC [ ? 3 h
 323 DECCOLM (default off = 80 columns): 80/132 col mode switch.
 324 The driver sources note that this alone does not suffice; some user-mode
 325 utility such as
 326 .BR resizecons (8)
 327 has to change the hardware registers on the console video card.
 328 .TP
 329 ESC [ ? 5 h
 330 DECSCNM (default off): Set reverse-video mode.
 331 .TP
 332 ESC [ ? 6 h
 333 DECOM (default off): When set, cursor addressing is relative to
 334 the upper left corner of the scrolling region.
 335 .TP
 336 ESC [ ? 7 h
 337 DECAWM (default on): Set autowrap on.
 338 In this mode, a graphic
 339 character emitted after column 80 (or column 132 of DECCOLM is on)
 340 forces a wrap to the beginning of the following line first.
 341 .TP
 342 ESC [ ? 8 h
 343 DECARM (default on): Set keyboard autorepeat on.
 344 .TP
 345 ESC [ ? 9 h
 346 X10 Mouse Reporting (default off): Set reporting mode to 1 (or reset to
 347 0)\(emsee below.
 348 .TP
 349 ESC [ ? 25 h
 350 DECTECM (default on): Make cursor visible.
 351 .TP
 352 ESC [ ? 1000 h
 353 X11 Mouse Reporting (default off): Set reporting mode to 2 (or reset
 354 to 0)\(emsee below.
 355 .\"
 356 .PP
 357 .B Linux Console Private CSI Sequences
 358 .PP
 359 .\"
 360 The following sequences are neither ECMA-48 nor native VT102.
 361 They are native to the Linux console driver.
 362 Colors are in SGR parameters:
 363 0 = black, 1 = red, 2 = green, 3 = brown, 4 = blue, 5 = magenta, 6 =
 364 cyan, 7 = white.
 365 .TS
 366 l l.
 367 ESC [ 1 ; \fIn\fP ]     Set color \fIn\fP as the underline color
 368 ESC [ 2 ; \fIn\fP ]     Set color \fIn\fP as the dim color
 369 ESC [ 8 ]               Make the current color pair the default attributes.
 370 ESC [ 9 ; \fIn\fP ]     Set screen blank timeout to \fIn\fP minutes.
 371 ESC [ 10 ; \fIn\fP ]    Set bell frequency in Hz.
 372 ESC [ 11 ; \fIn\fP ]    Set bell duration in msec.
 373 ESC [ 12 ; \fIn\fP ]    Bring specified console to the front.
 374 ESC [ 13 ]              Unblank the screen.
 375 ESC [ 14 ; \fIn\fP ]    Set the VESA powerdown interval in minutes.
 376 ESC [ 15 ]              T{
 377 Bring the previous console to the front
 378 (since Linux 2.6.0).
 379 T}
 380 ESC [ 16 ; \fIn\fP ]    T{
 381 Set the cursor blink interval in milliseconds
 382 (since Linux 4.2)
 383 T}
 384 .\" commit bd63364caa8df38bad2b25b11b2a1b849475cce5
 385 .TE
 386 .SS Character sets
 387 The kernel knows about 4 translations of bytes into console-screen
 388 symbols.
 389 The four tables are: a) Latin1 \-> PC,
 390 b) VT100 graphics \-> PC, c) PC \-> PC, d) user-defined.
 391 .PP
 392 There are two character sets, called G0 and G1, and one of them
 393 is the current character set.
 394 (Initially G0.)
 395 Typing \fB^N\fP causes G1 to become current,
 396 \fB^O\fP causes G0 to become current.
 397 .PP
 398 These variables G0 and G1 point at a translation table, and can be
 399 changed by the user.
 400 Initially they point at tables a) and b), respectively.
 401 The sequences ESC ( B and ESC ( 0 and ESC ( U and ESC ( K cause G0 to
 402 point at translation table a), b), c) and d), respectively.
 403 The sequences ESC ) B and ESC ) 0 and ESC ) U and ESC ) K cause G1 to
 404 point at translation table a), b), c) and d), respectively.
 405 .PP
 406 The sequence ESC c causes a terminal reset, which is what you want if the
 407 screen is all garbled.
 408 The oft-advised "echo ^V^O" will make only G0 current,
 409 but there is no guarantee that G0 points at table a).
 410 In some distributions there is a program
 411 .BR reset (1)
 412 that just does "echo ^[c".
 413 If your terminfo entry for the console is correct
 414 (and has an entry rs1=\eEc), then "tput reset" will also work.
 415 .PP
 416 The user-defined mapping table can be set using
 417 .BR mapscrn (8).
 418 The result of the mapping is that if a symbol c is printed, the symbol
 419 s = map[c] is sent to the video memory.
 420 The bitmap that corresponds to
 421 s is found in the character ROM, and can be changed using
 422 .BR setfont (8).
 423 .SS Mouse tracking
 424 The mouse tracking facility is intended to return
 425 .BR xterm (1)-compatible
 426 mouse status reports.
 427 Because the console driver has no way to know
 428 the device or type of the mouse, these reports are returned in the
 429 console input stream only when the virtual terminal driver receives
 430 a mouse update ioctl.
 431 These ioctls must be generated by a mouse-aware
 432 user-mode application such as the
 433 .BR gpm (8)
 434 daemon.
 435 .PP
 436 The mouse tracking escape sequences generated by
 437 \fBxterm\fP(1) encode numeric parameters in a single character as
 438 \fIvalue\fP+040.
 439 For example, \(aq!\(aq is 1.
 440 The screen coordinate system is 1-based.
 441 .PP
 442 The X10 compatibility mode sends an escape sequence on button press
 443 encoding the location and the mouse button pressed.
 444 It is enabled by sending ESC [ ? 9 h and disabled with ESC [ ? 9 l.
 445 On button press, \fBxterm\fP(1) sends
 446 ESC [ M \fIbxy\fP (6 characters).
 447 Here \fIb\fP is button\-1,
 448 and \fIx\fP and \fIy\fP are the x and y coordinates of the mouse
 449 when the button was pressed.
 450 This is the same code the kernel also produces.
 451 .PP
 452 Normal tracking mode (not implemented in Linux 2.0.24) sends an escape
 453 sequence on both button press and release.
 454 Modifier information is also sent.
 455 It is enabled by sending ESC [ ? 1000 h and disabled with
 456 ESC [ ? 1000 l.
 457 On button press or release, \fBxterm\fP(1) sends ESC [ M
 458 \fIbxy\fP.
 459 The low two bits of \fIb\fP encode button information:
 460 0=MB1 pressed, 1=MB2 pressed, 2=MB3 pressed, 3=release.
 461 The upper bits encode what modifiers were down when the button was
 462 pressed and are added together: 4=Shift, 8=Meta, 16=Control.
 463 Again \fIx\fP and
 464 \fIy\fP are the x and y coordinates of the mouse event.
 465 The upper left corner is (1,1).
 466 .SS Comparisons with other terminals
 467 Many different terminal types are described, like the Linux console,
 468 as being "VT100-compatible".
 469 Here we discuss differences between the
 470 Linux console and the two most important others, the DEC VT102 and
 471 .BR xterm (1).
 472 .\"
 473 .PP
 474 .B Control-character handling
 475 .PP
 476 The VT102 also recognized the following control characters:
 477 .HP
 478 NUL (0x00) was ignored;
 479 .HP
 480 ENQ (0x05) triggered an answerback message;
 481 .HP
 482 DC1 (0x11, \fB^Q\fP, XON) resumed transmission;
 483 .HP
 484 DC3 (0x13, \fB^S\fP, XOFF) caused VT100 to ignore (and stop transmitting)
 485 all codes except XOFF and XON.
 486 .PP
 487 VT100-like DC1/DC3 processing may be enabled by the terminal driver.
 488 .PP
 489 The
 490 .BR xterm (1)
 491 program (in VT100 mode) recognizes the control characters
 492 BEL, BS, HT, LF, VT, FF, CR, SO, SI, ESC.
 493 .\"
 494 .PP
 495 .B Escape sequences
 496 .PP
 497 VT100 console sequences not implemented on the Linux console:
 498 .TS
 499 l l l.
 500 ESC N   SS2     Single shift 2. (Select G2 character set for the next
 501                 character only.)
 502 ESC O   SS3     Single shift 3. (Select G3 character set for the next
 503                 character only.)
 504 ESC P   DCS     Device control string (ended by ESC \e)
 505 ESC X   SOS     Start of string.
 506 ESC ^   PM      Privacy message (ended by ESC \e)
 507 ESC \e  ST      String terminator
 508 ESC * ...               Designate G2 character set
 509 ESC + ...               Designate G3 character set
 510 .TE
 511 .PP
 512 The program
 513 .BR xterm (1)
 514 (in VT100 mode) recognizes ESC c, ESC # 8, ESC >, ESC =,
 515 ESC D, ESC E, ESC H, ESC M, ESC N, ESC O, ESC P ... ESC \e,
 516 ESC Z (it answers ESC [ ? 1 ; 2 c, "I am a VT100 with
 517 advanced video option")
 518 and ESC ^ ... ESC \e with the same meanings as indicated above.
 519 It accepts ESC (, ESC ), ESC *,  ESC + followed by 0, A, B for
 520 the DEC special character and line drawing set, UK, and US-ASCII,
 521 respectively.
 522 .PP
 523 The user can configure \fBxterm\fP(1) to respond to VT220-specific
 524 control sequences, and it will identify itself as a VT52, VT100, and
 525 up depending on the way it is configured and initialized.
 526 .PP
 527 It accepts ESC ] (OSC) for the setting of certain resources.
 528 In addition to the ECMA-48 string terminator (ST),
 529 \fBxterm\fP(1) accepts a BEL to terminate an OSC string.
 530 These are a few of the OSC control sequences recognized by \fBxterm\fP(1):
 531 .TS
 532 l l.
 533 ESC ] 0 ; \fItxt\fP ST  Set icon name and window title to \fItxt\fP.
 534 ESC ] 1 ; \fItxt\fP ST  Set icon name to \fItxt\fP.
 535 ESC ] 2 ; \fItxt\fP ST  Set window title to \fItxt\fP.
 536 ESC ] 4 ; \fInum\fP; \fItxt\fP ST       Set ANSI color \fInum\fP to \fItxt\fP.
 537 ESC ] 10 ; \fItxt\fP ST Set dynamic text color to \fItxt\fP.
 538 ESC ] 4 6 ; \fIname\fP ST       Change log file to \fIname\fP (normally disabled
 539         by a compile-time option)
 540 ESC ] 5 0 ; \fIfn\fP ST Set font to \fIfn\fP.
 541 .TE
 542 .PP
 543 It recognizes the following with slightly modified meaning
 544 (saving more state, behaving closer to VT100/VT220):
 545 .TS
 546 l l l.
 547 ESC 7  DECSC    Save cursor
 548 ESC 8  DECRC    Restore cursor
 549 .TE
 550 .PP
 551 It also recognizes
 552 .TS
 553 l l l.
 554 ESC F           Cursor to lower left corner of screen (if enabled by
 555                 \fBxterm\fP(1)'s \fBhpLowerleftBugCompat\fP resource)
 556 ESC l           Memory lock (per HP terminals).
 557                 Locks memory above the cursor.
 558 ESC m           Memory unlock (per HP terminals).
 559 ESC n   LS2     Invoke the G2 character set.
 560 ESC o   LS3     Invoke the G3 character set.
 561 ESC |   LS3R    Invoke the G3 character set as GR.
 562 ESC }   LS2R    Invoke the G2 character set as GR.
 563 ESC ~   LS1R    Invoke the G1 character set as GR.
 564 .TE
 565 .PP
 566 It also recognizes ESC % and provides a more complete UTF-8
 567 implementation than Linux console.
 568 .\"
 569 .PP
 570 .B CSI Sequences
 571 .PP
 572 Old versions of \fBxterm\fP(1), for example, from X11R5,
 573 interpret the blink SGR as a bold SGR.
 574 Later versions which implemented ANSI colors, for example,
 575 XFree86 3.1.2A in 1995, improved this by allowing
 576 the blink attribute to be displayed as a color.
 577 Modern versions of xterm implement blink SGR as blinking text
 578 and still allow colored text as an alternate rendering of SGRs.
 579 Stock X11R6 versions did not recognize the color-setting SGRs until
 580 the X11R6.8 release, which incorporated XFree86 xterm.
 581 All ECMA-48 CSI sequences recognized by Linux are also recognized by
 582 .IR xterm ,
 583 however \fBxterm\fP(1) implements several ECMA-48 and DEC control sequences
 584 not recognized by Linux.
 585 .PP
 586 The \fBxterm\fP(1)
 587 program recognizes all of the DEC Private Mode sequences listed
 588 above, but none of the Linux private-mode sequences.
 589 For discussion of \fBxterm\fP(1)'s
 590 own private-mode sequences, refer to the
 591 \fIXterm Control Sequences\fP
 592 document by
 593 Edward Moy,
 594 Stephen Gildea,
 595 and Thomas E.\& Dickey
 596 available with the X distribution.
 597 That document, though terse, is much longer than this manual page.
 598 For a chronological overview,
 599 .PP
 600 .RS
 601 .UR http://invisible\-island.net\:/xterm\:/xterm.log.html
 602 .UE
 603 .RE
 604 .PP
 605 details changes to xterm.
 606 .PP
 607 The \fIvttest\fP program
 608 .PP
 609 .RS
 610 .UR http://invisible\-island.net\:/vttest/
 611 .UE
 612 .RE
 613 .PP
 614 demonstrates many of these control sequences.
 615 The \fBxterm\fP(1) source distribution also contains sample
 616 scripts which exercise other features.
 617 .SH NOTES
 618 ESC 8 (DECRC) is not able to restore the character set changed with
 619 ESC %.
 620 .SH BUGS
 621 In 2.0.23, CSI is broken, and NUL is not ignored inside
 622 escape sequences.
 623 .PP
 624 Some older kernel versions (after 2.0) interpret 8-bit control
 625 sequences.
 626 These "C1 controls" use codes between 128 and 159 to replace
 627 ESC [, ESC ] and similar two-byte control sequence initiators.
 628 There are fragments of that in modern kernels (either overlooked or
 629 broken by changes to support UTF-8),
 630 but the implementation is incomplete and should be regarded
 631 as unreliable.
 632 .PP
 633 Linux "private mode" sequences do not follow the rules in ECMA-48
 634 for private mode control sequences.
 635 In particular, those ending with ] do not use a standard terminating
 636 character.
 637 The OSC (set palette) sequence is a greater problem,
 638 since \fBxterm\fP(1) may interpret this as a control sequence
 639 which requires a string terminator (ST).
 640 Unlike the \fBsetterm\fP(1) sequences which will be ignored (since
 641 they are invalid control sequences), the palette sequence will make
 642 \fBxterm\fP(1) appear to hang (though pressing the return-key
 643 will fix that).
 644 To accommodate applications which have been hardcoded to use Linux
 645 control sequences,
 646 set the \fBxterm\fP(1) resource \fBbrokenLinuxOSC\fP to true.
 647 .PP
 648 An older version of this document implied that Linux recognizes the
 649 ECMA-48 control sequence for invisible text.
 650 It is ignored.
 651 .SH SEE ALSO
 652 .BR ioctl_console (2),
 653 .BR charsets (7)