1console_codes(4) Kernel Interfaces Manual console_codes(4)
2
6 console_codes - Linux console escape and control sequences
7
9 The Linux console implements a large subset of the VT102 and
10 ECMA-48/ISO 6429/ANSI X3.64 terminal controls, plus certain private-
11 mode sequences for changing the color palette, character-set mapping,
12 and so on. In the tabular descriptions below, the second column gives
13 ECMA-48 or DEC mnemonics (the latter if prefixed with DEC) for the
14 given function. Sequences without a mnemonic are neither ECMA-48 nor
15 VT102.
16 After all the normal output processing has been done, and a stream of
18 characters arrives at the console driver for actual printing, the first
19 thing that happens is a translation from the code used for processing
20 to the code used for printing.
21 If the console is in UTF-8 mode, then the incoming bytes are first as‐
23 sembled into 16-bit Unicode codes. Otherwise, each byte is transformed
24 according to the current mapping table (which translates it to a Uni‐
25 code value). See the Character Sets section below for discussion.
26 In the normal case, the Unicode value is converted to a font index, and
28 this is stored in video memory, so that the corresponding glyph (as
29 found in video ROM) appears on the screen. Note that the use of Uni‐
30 code (and the design of the PC hardware) allows us to use 512 different
31 glyphs simultaneously.
32 If the current Unicode value is a control character, or we are cur‐
34 rently processing an escape sequence, the value will treated specially.
35 Instead of being turned into a font index and rendered as a glyph, it
36 may trigger cursor movement or other control functions. See the Linux
37 Console Controls section below for discussion.
38 It is generally not good practice to hard-wire terminal controls into
40 programs. Linux supports a terminfo(5) database of terminal capabili‐
41 ties. Rather than emitting console escape sequences by hand, you will
42 almost always want to use a terminfo-aware screen library or utility
43 such as ncurses(3), tput(1), or reset(1).
44 Linux console controls
46 This section describes all the control characters and escape sequences
47 that invoke special functions (i.e., anything other than writing a
48 glyph at the current cursor location) on the Linux console.
49 Control characters
51 A character is a control character if (before transformation according
53 to the mapping table) it has one of the 14 codes 00 (NUL), 07 (BEL), 08
54 (BS), 09 (HT), 0a (LF), 0b (VT), 0c (FF), 0d (CR), 0e (SO), 0f (SI), 18
55 (CAN), 1a (SUB), 1b (ESC), 7f (DEL). One can set a "display control
56 characters" mode (see below), and allow 07, 09, 0b, 18, 1a, 7f to be
57 displayed as glyphs. On the other hand, in UTF-8 mode all codes 00–1f
58 are regarded as control characters, regardless of any "display control
59 characters" mode.
60 If we have a control character, it is acted upon immediately and then
62 discarded (even in the middle of an escape sequence) and the escape se‐
63 quence continues with the next character. (However, ESC starts a new
64 escape sequence, possibly aborting a previous unfinished one, and CAN
65 and SUB abort any escape sequence.) The recognized control characters
66 are BEL, BS, HT, LF, VT, FF, CR, SO, SI, CAN, SUB, ESC, DEL, CSI. They
67 do what one would expect:
68 BEL (0x07, ^G)
70 beeps;
71 BS (0x08, ^H)
73 backspaces one column (but not past the beginning of the line);
74 HT (0x09, ^I)
76 goes to the next tab stop or to the end of the line if there is
77 no earlier tab stop;
78 LF (0x0A, ^J)
80 VT (0x0B, ^K)
81 FF (0x0C, ^L)
82 all give a linefeed, and if LF/NL (new-line mode) is set also a
83 carriage return;
84 CR (0x0D, ^M)
86 gives a carriage return;
87 SO (0x0E, ^N)
89 activates the G1 character set;
90 SI (0x0F, ^O)
92 activates the G0 character set;
93 CAN (0x18, ^X)
95 SUB (0x1A, ^Z)
96 abort escape sequences;
97 ESC (0x1B, ^[)
99 starts an escape sequence;
100 DEL (0x7F)
102 is ignored;
103 CSI (0x9B)
105 is equivalent to ESC [.
106 ESC- but not CSI-sequences
108 ESC c RIS Reset.
110 ESC D IND Linefeed.
111 ESC E NEL Newline.
112 ESC H HTS Set tab stop at current column.
113 ESC M RI Reverse linefeed.
114 ESC Z DECID DEC private identification. The kernel returns the
115 string ESC [ ? 6 c, claiming that it is a VT102.
116 ESC 7 DECSC Save current state (cursor coordinates, attributes,
117 character sets pointed at by G0, G1).
118 ESC 8 DECRC Restore state most recently saved by ESC 7.
119 ESC % Start sequence selecting character set
120 ESC % @ Select default (ISO 646 / ISO 8859-1)
121 ESC % G Select UTF-8
122 ESC % 8 Select UTF-8 (obsolete)
123 ESC # 8 DECALN DEC screen alignment test - fill screen with E's.
124 ESC ( Start sequence defining G0 character set (followed
125 by one of B, 0, U, K, as below)
126 ESC ( B Select default (ISO 8859-1 mapping).
127 ESC ( 0 Select VT100 graphics mapping.
128 ESC ( U Select null mapping - straight to character ROM.
129 ESC ( K Select user mapping - the map that is loaded by the
130 utility mapscrn(8).
131 ESC ) Start sequence defining G1 (followed by one of B, 0,
134 U, K, as above).
135 ESC > DECPNM Set numeric keypad mode
136 ESC = DECPAM Set application keypad mode
137 ESC ] OSC Operating System Command prefix.
138 ESC ] R Reset palette.
139 ESC ] P Set palette, with parameter given in 7 hexadecimal
140 digits nrrggbb after the final P. Here n is the
141 color (0–15), and rrggbb indicates the
142 red/green/blue values (0–255).
143 ECMA-48 CSI sequences
145 CSI (or ESC [) is followed by a sequence of parameters, at most NPAR
147 (16), that are decimal numbers separated by semicolons. An empty or
148 absent parameter is taken to be 0. The sequence of parameters may be
149 preceded by a single question mark.
150 However, after CSI [ (or ESC [ [) a single character is read and this
152 entire sequence is ignored. (The idea is to ignore an echoed function
153 key.)
154 The action of a CSI sequence is determined by its final character.
156 @ ICH Insert the indicated # of blank characters.
158 A CUU Move cursor up the indicated # of rows.
159 B CUD Move cursor down the indicated # of rows.
160 C CUF Move cursor right the indicated # of columns.
161 D CUB Move cursor left the indicated # of columns.
162 E CNL Move cursor down the indicated # of rows, to column 1.
163 F CPL Move cursor up the indicated # of rows, to column 1.
164 G CHA Move cursor to indicated column in current row.
165 H CUP Move cursor to the indicated row, column (origin at 1,1).
166 J ED Erase display (default: from cursor to end of display).
167 ESC [ 1 J: erase from start to cursor.
168 ESC [ 2 J: erase whole display.
169 ESC [ 3 J: erase whole display including scroll-back buf‐
170 fer (since Linux 3.0).
171 K EL Erase line (default: from cursor to end of line).
172 ESC [ 1 K: erase from start of line to cursor.
173 ESC [ 2 K: erase whole line.
174 L IL Insert the indicated # of blank lines.
175 M DL Delete the indicated # of lines.
176 P DCH Delete the indicated # of characters on current line.
177 X ECH Erase the indicated # of characters on current line.
178 a HPR Move cursor right the indicated # of columns.
179 c DA Answer ESC [ ? 6 c: "I am a VT102".
180 d VPA Move cursor to the indicated row, current column.
181 e VPR Move cursor down the indicated # of rows.
182 f HVP Move cursor to the indicated row, column.
183 g TBC Without parameter: clear tab stop at current position.
184 ESC [ 3 g: delete all tab stops.
185 h SM Set Mode (see below).
186 l RM Reset Mode (see below).
187 m SGR Set attributes (see below).
188 n DSR Status report (see below).
189 q DECLL Set keyboard LEDs.
190 ESC [ 0 q: clear all LEDs
191 ESC [ 1 q: set Scroll Lock LED
192 ESC [ 2 q: set Num Lock LED
193 ESC [ 3 q: set Caps Lock LED
194 r DECSTBM Set scrolling region; parameters are top and bottom row.
195 s ? Save cursor location.
196 u ? Restore cursor location.
197 ` HPA Move cursor to indicated column in current row.
198 ECMA-48 Select Graphic Rendition
200 The ECMA-48 SGR sequence ESC [ parameters m sets display attributes.
202 Several attributes can be set in the same sequence, separated by semi‐
203 colons. An empty parameter (between semicolons or string initiator or
204 terminator) is interpreted as a zero.
205 param result
207 0 reset all attributes to their defaults
208 1 set bold
209 2 set half-bright (simulated with color on a color display)
210 3 set italic (since Linux 2.6.22; simulated with color on a color display)
211 4 set underscore (simulated with color on a color display) (the colors
212 used to simulate dim or underline are set using ESC ] ...)
213 5 set blink
214 7 set reverse video
215 10 reset selected mapping, display control flag, and toggle meta flag
216 (ECMA-48 says "primary font").
217 11 select null mapping, set display control flag, reset toggle meta flag
218 (ECMA-48 says "first alternate font").
219 12 select null mapping, set display control flag, set toggle meta flag
220 (ECMA-48 says "second alternate font"). The toggle meta flag causes the
221 high bit of a byte to be toggled before the mapping table translation is
222 done.
223 21 set underline; before Linux 4.17, this value set normal intensity (as is
224 done in many other terminals)
225 22 set normal intensity
226 23 italic off (since Linux 2.6.22)
227 24 underline off
228 25 blink off
229 27 reverse video off
230 30 set black foreground
231 31 set red foreground
232 32 set green foreground
233 33 set brown foreground
234 34 set blue foreground
235 35 set magenta foreground
236 36 set cyan foreground
237 37 set white foreground
238 38 256/24-bit foreground color follows, shoehorned into 16 basic colors
239 (before Linux 3.16: set underscore on, set default foreground color)
240 39 set default foreground color (before Linux 3.16: set underscore off, set
241 default foreground color)
242 40 set black background
243 41 set red background
244 42 set green background
245 43 set brown background
246 44 set blue background
247 45 set magenta background
248 46 set cyan background
249 47 set white background
250 48 256/24-bit background color follows, shoehorned into 8 basic colors
251 49 set default background color
252 90..97 set foreground to bright versions of 30..37
253 100..107 set background, same as 40..47 (bright not supported)
254 Commands 38 and 48 require further arguments:
256 ;5;x 256 color: values 0..15 are IBGR (black, red, green, ...
258 white), 16..231 a 6x6x6 color cube, 232..255 a grayscale
259 ramp
260 ;2;r;g;b 24-bit color, r/g/b components are in the range 0..255
261 ECMA-48 Mode Switches
263 ESC [ 3 h
265 DECCRM (default off): Display control chars.
266 ESC [ 4 h
268 DECIM (default off): Set insert mode.
269 ESC [ 20 h
271 LF/NL (default off): Automatically follow echo of LF, VT, or FF
272 with CR.
273 ECMA-48 Status Report Commands
275 ESC [ 5 n
277 Device status report (DSR): Answer is ESC [ 0 n (Terminal OK).
278 ESC [ 6 n
280 Cursor position report (CPR): Answer is ESC [ y ; x R, where x,y
281 is the cursor location.
282 DEC Private Mode (DECSET/DECRST) sequences
284 These are not described in ECMA-48. We list the Set Mode sequences;
286 the Reset Mode sequences are obtained by replacing the final 'h' by
287 'l'.
288 ESC [ ? 1 h
290 DECCKM (default off): When set, the cursor keys send an ESC O
291 prefix, rather than ESC [.
292 ESC [ ? 3 h
294 DECCOLM (default off = 80 columns): 80/132 col mode switch. The
295 driver sources note that this alone does not suffice; some user-
296 mode utility such as resizecons(8) has to change the hardware
297 registers on the console video card.
298 ESC [ ? 5 h
300 DECSCNM (default off): Set reverse-video mode.
301 ESC [ ? 6 h
303 DECOM (default off): When set, cursor addressing is relative to
304 the upper left corner of the scrolling region.
305 ESC [ ? 7 h
307 DECAWM (default on): Set autowrap on. In this mode, a graphic
308 character emitted after column 80 (or column 132 of DECCOLM is
309 on) forces a wrap to the beginning of the following line first.
310 ESC [ ? 8 h
312 DECARM (default on): Set keyboard autorepeat on.
313 ESC [ ? 9 h
315 X10 Mouse Reporting (default off): Set reporting mode to 1 (or
316 reset to 0)—see below.
317 ESC [ ? 25 h
319 DECTECM (default on): Make cursor visible.
320 ESC [ ? 1000 h
322 X11 Mouse Reporting (default off): Set reporting mode to 2 (or
323 reset to 0)—see below.
324 Linux Console Private CSI Sequences
326 The following sequences are neither ECMA-48 nor native VT102. They are
328 native to the Linux console driver. Colors are in SGR parameters: 0 =
329 black, 1 = red, 2 = green, 3 = brown, 4 = blue, 5 = magenta, 6 = cyan,
330 7 = white; 8–15 = bright versions of 0–7.
331 ESC [ 1 ; n ] Set color n as the underline color.
333 ESC [ 2 ; n ] Set color n as the dim color.
334 ESC [ 8 ] Make the current color pair the default attributes.
336 ESC [ 9 ; n ] Set screen blank timeout to n minutes.
337 ESC [ 10 ; n ] Set bell frequency in Hz.
338 ESC [ 11 ; n ] Set bell duration in msec.
339 ESC [ 12 ; n ] Bring specified console to the front.
340 ESC [ 13 ] Unblank the screen.
341 ESC [ 14 ; n ] Set the VESA powerdown interval in minutes.
342 ESC [ 15 ] Bring the previous console to the front (since
343 Linux 2.6.0).
344 ESC [ 16 ; n ] Set the cursor blink interval in milliseconds
345 (since Linux 4.2).
346 Character sets
348 The kernel knows about 4 translations of bytes into console-screen sym‐
349 bols. The four tables are: a) Latin1 -> PC, b) VT100 graphics -> PC,
350 c) PC -> PC, d) user-defined.
351 There are two character sets, called G0 and G1, and one of them is the
353 current character set. (Initially G0.) Typing ^N causes G1 to become
354 current, ^O causes G0 to become current.
355 These variables G0 and G1 point at a translation table, and can be
357 changed by the user. Initially they point at tables a) and b), respec‐
358 tively. The sequences ESC ( B and ESC ( 0 and ESC ( U and ESC ( K
359 cause G0 to point at translation table a), b), c), and d), respec‐
360 tively. The sequences ESC ) B and ESC ) 0 and ESC ) U and ESC ) K
361 cause G1 to point at translation table a), b), c), and d), respec‐
362 tively.
363 The sequence ESC c causes a terminal reset, which is what you want if
365 the screen is all garbled. The oft-advised "echo ^V^O" will make only
366 G0 current, but there is no guarantee that G0 points at table a). In
367 some distributions there is a program reset(1) that just does "echo
368 ^[c". If your terminfo entry for the console is correct (and has an
369 entry rs1=\Ec), then "tput reset" will also work.
370 The user-defined mapping table can be set using mapscrn(8). The result
372 of the mapping is that if a symbol c is printed, the symbol s = map[c]
373 is sent to the video memory. The bitmap that corresponds to s is found
374 in the character ROM, and can be changed using setfont(8).
375 Mouse tracking
377 The mouse tracking facility is intended to return xterm(1)-compatible
378 mouse status reports. Because the console driver has no way to know
379 the device or type of the mouse, these reports are returned in the con‐
380 sole input stream only when the virtual terminal driver receives a
381 mouse update ioctl. These ioctls must be generated by a mouse-aware
382 user-mode application such as the gpm(8) daemon.
383 The mouse tracking escape sequences generated by xterm(1) encode nu‐
385 meric parameters in a single character as value+040. For example, '!'
386 is 1. The screen coordinate system is 1-based.
387 The X10 compatibility mode sends an escape sequence on button press en‐
389 coding the location and the mouse button pressed. It is enabled by
390 sending ESC [ ? 9 h and disabled with ESC [ ? 9 l. On button press,
391 xterm(1) sends ESC [ M bxy (6 characters). Here b is button-1, and x
392 and y are the x and y coordinates of the mouse when the button was
393 pressed. This is the same code the kernel also produces.
394 Normal tracking mode (not implemented in Linux 2.0.24) sends an escape
396 sequence on both button press and release. Modifier information is
397 also sent. It is enabled by sending ESC [ ? 1000 h and disabled with
398 ESC [ ? 1000 l. On button press or release, xterm(1) sends ESC [ M
399 bxy. The low two bits of b encode button information: 0=MB1 pressed,
400 1=MB2 pressed, 2=MB3 pressed, 3=release. The upper bits encode what
401 modifiers were down when the button was pressed and are added together:
402 4=Shift, 8=Meta, 16=Control. Again x and y are the x and y coordinates
403 of the mouse event. The upper left corner is (1,1).
404 Comparisons with other terminals
406 Many different terminal types are described, like the Linux console, as
407 being "VT100-compatible". Here we discuss differences between the
408 Linux console and the two most important others, the DEC VT102 and
409 xterm(1).
410 Control-character handling
412 The VT102 also recognized the following control characters:
414 NUL (0x00)
416 was ignored;
417 ENQ (0x05)
419 triggered an answerback message;
420 DC1 (0x11, ^Q, XON)
422 resumed transmission;
423 DC3 (0x13, ^S, XOFF)
425 caused VT100 to ignore (and stop transmitting) all codes except
426 XOFF and XON.
427 VT100-like DC1/DC3 processing may be enabled by the terminal driver.
429 The xterm(1) program (in VT100 mode) recognizes the control characters
431 BEL, BS, HT, LF, VT, FF, CR, SO, SI, ESC.
432 Escape sequences
434 VT100 console sequences not implemented on the Linux console:
436 ESC N SS2 Single shift 2. (Select G2 char‐
438 acter set for the next character
439 only.)
440 ESC O SS3 Single shift 3. (Select G3 char‐
441 acter set for the next character
442 only.)
443 ESC P DCS Device control string (ended by
444 ESC \)
445 ESC X SOS Start of string.
446 ESC ^ PM Privacy message (ended by ESC \)
447 ESC \ ST String terminator
448 ESC * ... Designate G2 character set
449 ESC + ... Designate G3 character set
450 The program xterm(1) (in VT100 mode) recognizes ESC c, ESC # 8, ESC >,
452 ESC =, ESC D, ESC E, ESC H, ESC M, ESC N, ESC O, ESC P ... ESC \, ESC Z
453 (it answers ESC [ ? 1 ; 2 c, "I am a VT100 with advanced video option")
454 and ESC ^ ... ESC \ with the same meanings as indicated above. It ac‐
455 cepts ESC (, ESC ), ESC *, ESC + followed by 0, A, B for the DEC spe‐
456 cial character and line drawing set, UK, and US-ASCII, respectively.
457 The user can configure xterm(1) to respond to VT220-specific control
459 sequences, and it will identify itself as a VT52, VT100, and up depend‐
460 ing on the way it is configured and initialized.
461 It accepts ESC ] (OSC) for the setting of certain resources. In addi‐
463 tion to the ECMA-48 string terminator (ST), xterm(1) accepts a BEL to
464 terminate an OSC string. These are a few of the OSC control sequences
465 recognized by xterm(1):
466 ESC ] 0 ; txt ST Set icon name and window title
468 to txt.
469 ESC ] 1 ; txt ST Set icon name to txt.
470 ESC ] 2 ; txt ST Set window title to txt.
472 ESC ] 4 ; num; txt ST Set ANSI color num to txt.
473 ESC ] 10 ; txt ST Set dynamic text color to txt.
474 ESC ] 4 6 ; name ST Change log file to name (nor‐
475 mally disabled by a compile-
476 time option).
477 ESC ] 5 0 ; fn ST Set font to fn.
478 It recognizes the following with slightly modified meaning (saving more
480 state, behaving closer to VT100/VT220):
481 ESC 7 DECSC Save cursor
483 ESC 8 DECRC Restore cursor
484 It also recognizes
486 ESC F Cursor to lower left corner of screen (if enabled by
488 xterm(1)'s hpLowerleftBugCompat resource).
489 ESC l Memory lock (per HP terminals).
490 Locks memory above the cursor.
491 ESC m Memory unlock (per HP terminals).
492 ESC n LS2 Invoke the G2 character set.
493 ESC o LS3 Invoke the G3 character set.
494 ESC | LS3R Invoke the G3 character set as GR.
495 ESC } LS2R Invoke the G2 character set as GR.
496 ESC ~ LS1R Invoke the G1 character set as GR.
497 It also recognizes ESC % and provides a more complete UTF-8 implementa‐
499 tion than Linux console.
500 CSI Sequences
502 Old versions of xterm(1), for example, from X11R5, interpret the blink
504 SGR as a bold SGR. Later versions which implemented ANSI colors, for
505 example, XFree86 3.1.2A in 1995, improved this by allowing the blink
506 attribute to be displayed as a color. Modern versions of xterm imple‐
507 ment blink SGR as blinking text and still allow colored text as an al‐
508 ternate rendering of SGRs. Stock X11R6 versions did not recognize the
509 color-setting SGRs until the X11R6.8 release, which incorporated
510 XFree86 xterm. All ECMA-48 CSI sequences recognized by Linux are also
511 recognized by xterm, however xterm(1) implements several ECMA-48 and
512 DEC control sequences not recognized by Linux.
513 The xterm(1) program recognizes all of the DEC Private Mode sequences
515 listed above, but none of the Linux private-mode sequences. For dis‐
516 cussion of xterm(1)'s own private-mode sequences, refer to the Xterm
517 Control Sequences document by Edward Moy, Stephen Gildea, and Thomas E.
518 Dickey available with the X distribution. That document, though terse,
519 is much longer than this manual page. For a chronological overview,
520 ⟨http://invisible-island.net/xterm/xterm.log.html⟩
522 details changes to xterm.
524 The vttest program
526 ⟨http://invisible-island.net/vttest/⟩
528 demonstrates many of these control sequences. The xterm(1) source dis‐
530 tribution also contains sample scripts which exercise other features.
531
533 ESC 8 (DECRC) is not able to restore the character set changed with ESC
534 %.
535
537 In Linux 2.0.23, CSI is broken, and NUL is not ignored inside escape
538 sequences.
539 Some older kernel versions (after Linux 2.0) interpret 8-bit control
541 sequences. These "C1 controls" use codes between 128 and 159 to re‐
542 place ESC [, ESC ] and similar two-byte control sequence initiators.
543 There are fragments of that in modern kernels (either overlooked or
544 broken by changes to support UTF-8), but the implementation is incom‐
545 plete and should be regarded as unreliable.
546 Linux "private mode" sequences do not follow the rules in ECMA-48 for
548 private mode control sequences. In particular, those ending with ] do
549 not use a standard terminating character. The OSC (set palette) se‐
550 quence is a greater problem, since xterm(1) may interpret this as a
551 control sequence which requires a string terminator (ST). Unlike the
552 setterm(1) sequences which will be ignored (since they are invalid con‐
553 trol sequences), the palette sequence will make xterm(1) appear to hang
554 (though pressing the return-key will fix that). To accommodate appli‐
555 cations which have been hardcoded to use Linux control sequences, set
556 the xterm(1) resource brokenLinuxOSC to true.
557 An older version of this document implied that Linux recognizes the
559 ECMA-48 control sequence for invisible text. It is ignored.
560
562 ioctl_console(2), charsets(7)
563Linux man-pages 6.05 2023-02-05 console_codes(4)