1CONSOLE_CODES(4) Linux Programmer's Manual CONSOLE_CODES(4)
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6 console_codes - Linux console escape and control sequences
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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
17 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.
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22 If the console is in UTF-8 mode, then the incoming bytes are first
23 assembled into 16-bit Unicode codes. Otherwise each byte is trans‐
24 formed according to the current mapping table (which translates it to a
25 Unicode value). See the Character Sets section below for discussion.
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27 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
33 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
39 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).
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45 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.
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50 Control characters
51
52 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
61 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
63 sequence 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:
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69 BEL (0x07, ^G) beeps;
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71 BS (0x08, ^H) backspaces one column (but not past the beginning of the
72 line);
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74 HT (0x09, ^I) goes to the next tab stop or to the end of the line if
75 there is no earlier tab stop;
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77 LF (0x0A, ^J), VT (0x0B, ^K) and FF (0x0C, ^L) all give a linefeed, and
78 if LF/NL (new-line mode) is set also a carriage return;
79
80 CR (0x0D, ^M) gives a carriage return;
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82 SO (0x0E, ^N) activates the G1 character set;
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84 SI (0x0F, ^O) activates the G0 character set;
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86 CAN (0x18, ^X) and SUB (0x1A, ^Z) interrupt escape sequences;
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88 ESC (0x1B, ^[) starts an escape sequence;
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90 DEL (0x7F) is ignored;
91
92 CSI (0x9B) is equivalent to ESC [.
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94 ESC- but not CSI-sequences
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96 ESC c RIS Reset.
97 ESC D IND Linefeed.
98 ESC E NEL Newline.
99 ESC H HTS Set tab stop at current column.
100 ESC M RI Reverse linefeed.
101 ESC Z DECID DEC private identification. The kernel returns the
102 string ESC [ ? 6 c, claiming that it is a VT102.
103 ESC 7 DECSC Save current state (cursor coordinates,
104 attributes, character sets pointed at by G0, G1).
105 ESC 8 DECRC Restore state most recently saved by ESC 7.
106 ESC [ CSI Control sequence introducer
107 ESC % Start sequence selecting character set
108 ESC % @ Select default (ISO 646 / ISO 8859-1)
109 ESC % G Select UTF-8
110 ESC % 8 Select UTF-8 (obsolete)
111 ESC # 8 DECALN DEC screen alignment test - fill screen with E's.
112 ESC ( Start sequence defining G0 character set
113 ESC ( B Select default (ISO 8859-1 mapping)
114 ESC ( 0 Select VT100 graphics mapping
115 ESC ( U Select null mapping - straight to character ROM
116 ESC ( K Select user mapping - the map that is loaded by
117 the utility mapscrn(8).
118 ESC ) Start sequence defining G1
119 (followed by one of B, 0, U, K, as above).
120 ESC > DECPNM Set numeric keypad mode
121 ESC = DECPAM Set application keypad mode
122 ESC ] OSC (Should be: Operating system command) ESC ] P
123 nrrggbb: set palette, with parameter given in 7
124 hexadecimal digits after the final P :-(. Here n
125 is the color (0-15), and rrggbb indicates the
126 red/green/blue values (0-255). ESC ] R: reset
127 palette
128
129 ECMA-48 CSI sequences
130
131 CSI (or ESC [) is followed by a sequence of parameters, at most NPAR
132 (16), that are decimal numbers separated by semicolons. An empty or
133 absent parameter is taken to be 0. The sequence of parameters may be
134 preceded by a single question mark.
135
136 However, after CSI [ (or ESC [ [) a single character is read and this
137 entire sequence is ignored. (The idea is to ignore an echoed function
138 key.)
139
140 The action of a CSI sequence is determined by its final character.
141
142 @ ICH Insert the indicated # of blank characters.
143 A CUU Move cursor up the indicated # of rows.
144 B CUD Move cursor down the indicated # of rows.
145 C CUF Move cursor right the indicated # of columns.
146 D CUB Move cursor left the indicated # of columns.
147 E CNL Move cursor down the indicated # of rows, to column 1.
148 F CPL Move cursor up the indicated # of rows, to column 1.
149 G CHA Move cursor to indicated column in current row.
150 H CUP Move cursor to the indicated row, column (origin at 1,1).
151 J ED Erase display (default: from cursor to end of display).
152 ESC [ 1 J: erase from start to cursor.
153 ESC [ 2 J: erase whole display.
154 ESC [ 3 J: erase whole display including scroll-back
155 buffer (since Linux 3.0).
156 K EL Erase line (default: from cursor to end of line).
157 ESC [ 1 K: erase from start of line to cursor.
158 ESC [ 2 K: erase whole line.
159 L IL Insert the indicated # of blank lines.
160 M DL Delete the indicated # of lines.
161 P DCH Delete the indicated # of characters on current line.
162 X ECH Erase the indicated # of characters on current line.
163 a HPR Move cursor right the indicated # of columns.
164 c DA Answer ESC [ ? 6 c: "I am a VT102".
165 d VPA Move cursor to the indicated row, current column.
166 e VPR Move cursor down the indicated # of rows.
167 f HVP Move cursor to the indicated row, column.
168 g TBC Without parameter: clear tab stop at current position.
169 ESC [ 3 g: delete all tab stops.
170 h SM Set Mode (see below).
171 l RM Reset Mode (see below).
172 m SGR Set attributes (see below).
173 n DSR Status report (see below).
174 q DECLL Set keyboard LEDs.
175 ESC [ 0 q: clear all LEDs
176 ESC [ 1 q: set Scroll Lock LED
177 ESC [ 2 q: set Num Lock LED
178 ESC [ 3 q: set Caps Lock LED
179 r DECSTBM Set scrolling region; parameters are top and bottom row.
180 s ? Save cursor location.
181 u ? Restore cursor location.
182 ` HPA Move cursor to indicated column in current row.
183
184 ECMA-48 Set Graphics Rendition
185
186 The ECMA-48 SGR sequence ESC [ parameters m sets display attributes.
187 Several attributes can be set in the same sequence, separated by semi‐
188 colons. An empty parameter (between semicolons or string initiator or
189 terminator) is interpreted as a zero.
190
191 param result
192 0 reset all attributes to their defaults
193 1 set bold
194 2 set half-bright (simulated with color on a color display)
195 4 set underscore (simulated with color on a color display)
196 (the colors used to simulate dim or underline are set
197 using ESC ] ...)
198
199 5 set blink
200 7 set reverse video
201 10 reset selected mapping, display control flag, and toggle
202 meta flag (ECMA-48 says "primary font").
203 11 select null mapping, set display control flag, reset tog‐
204 gle meta flag (ECMA-48 says "first alternate font").
205 12 select null mapping, set display control flag, set toggle
206 meta flag (ECMA-48 says "second alternate font"). The
207 toggle meta flag causes the high bit of a byte to be tog‐
208 gled before the mapping table translation is done.
209 21 set normal intensity (ECMA-48 says "doubly underlined")
210 22 set normal intensity
211 24 underline off
212 25 blink off
213 27 reverse video off
214 30 set black foreground
215 31 set red foreground
216 32 set green foreground
217 33 set brown foreground
218 34 set blue foreground
219 35 set magenta foreground
220 36 set cyan foreground
221 37 set white foreground
222 38 set underscore on, set default foreground color
223 39 set underscore off, set default foreground color
224 40 set black background
225 41 set red background
226 42 set green background
227 43 set brown background
228 44 set blue background
229 45 set magenta background
230 46 set cyan background
231 47 set white background
232 49 set default background color
233
234 ECMA-48 Mode Switches
235
236 ESC [ 3 h
237 DECCRM (default off): Display control chars.
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239 ESC [ 4 h
240 DECIM (default off): Set insert mode.
241
242 ESC [ 20 h
243 LF/NL (default off): Automatically follow echo of LF, VT or FF
244 with CR.
245
246 ECMA-48 Status Report Commands
247
248 ESC [ 5 n
249 Device status report (DSR): Answer is ESC [ 0 n (Terminal OK).
250
251 ESC [ 6 n
252 Cursor position report (CPR): Answer is ESC [ y ; x R, where x,y
253 is the cursor location.
254
255 DEC Private Mode (DECSET/DECRST) sequences
256
257 These are not described in ECMA-48. We list the Set Mode sequences;
258 the Reset Mode sequences are obtained by replacing the final 'h' by
259 'l'.
260
261 ESC [ ? 1 h
262 DECCKM (default off): When set, the cursor keys send an ESC O
263 prefix, rather than ESC [.
264
265 ESC [ ? 3 h
266 DECCOLM (default off = 80 columns): 80/132 col mode switch. The
267 driver sources note that this alone does not suffice; some user-
268 mode utility such as resizecons(8) has to change the hardware
269 registers on the console video card.
270
271 ESC [ ? 5 h
272 DECSCNM (default off): Set reverse-video mode.
273
274 ESC [ ? 6 h
275 DECOM (default off): When set, cursor addressing is relative to
276 the upper left corner of the scrolling region.
277
278 ESC [ ? 7 h
279 DECAWM (default on): Set autowrap on. In this mode, a graphic
280 character emitted after column 80 (or column 132 of DECCOLM is
281 on) forces a wrap to the beginning of the following line first.
282
283 ESC [ ? 8 h
284 DECARM (default on): Set keyboard autorepeat on.
285
286 ESC [ ? 9 h
287 X10 Mouse Reporting (default off): Set reporting mode to 1 (or
288 reset to 0)—see below.
289
290 ESC [ ? 25 h
291 DECTECM (default on): Make cursor visible.
292
293 ESC [ ? 1000 h
294 X11 Mouse Reporting (default off): Set reporting mode to 2 (or
295 reset to 0)—see below.
296
297 Linux Console Private CSI Sequences
298
299 The following sequences are neither ECMA-48 nor native VT102. They are
300 native to the Linux console driver. Colors are in SGR parameters: 0 =
301 black, 1 = red, 2 = green, 3 = brown, 4 = blue, 5 = magenta, 6 = cyan,
302 7 = white.
303
304 ESC [ 1 ; n ] Set color n as the underline color
305 ESC [ 2 ; n ] Set color n as the dim color
306 ESC [ 8 ] Make the current color pair the default attributes.
307 ESC [ 9 ; n ] Set screen blank timeout to n minutes.
308 ESC [ 10 ; n ] Set bell frequency in Hz.
309 ESC [ 11 ; n ] Set bell duration in msec.
310 ESC [ 12 ; n ] Bring specified console to the front.
311 ESC [ 13 ] Unblank the screen.
312 ESC [ 14 ; n ] Set the VESA powerdown interval in minutes.
313
314 Character sets
315 The kernel knows about 4 translations of bytes into console-screen sym‐
316 bols. The four tables are: a) Latin1 -> PC, b) VT100 graphics -> PC,
317 c) PC -> PC, d) user-defined.
318
319 There are two character sets, called G0 and G1, and one of them is the
320 current character set. (Initially G0.) Typing ^N causes G1 to become
321 current, ^O causes G0 to become current.
322
323 These variables G0 and G1 point at a translation table, and can be
324 changed by the user. Initially they point at tables a) and b), respec‐
325 tively. The sequences ESC ( B and ESC ( 0 and ESC ( U and ESC ( K
326 cause G0 to point at translation table a), b), c) and d), respectively.
327 The sequences ESC ) B and ESC ) 0 and ESC ) U and ESC ) K cause G1 to
328 point at translation table a), b), c) and d), respectively.
329
330 The sequence ESC c causes a terminal reset, which is what you want if
331 the screen is all garbled. The oft-advised "echo ^V^O" will make only
332 G0 current, but there is no guarantee that G0 points at table a). In
333 some distributions there is a program reset(1) that just does "echo
334 ^[c". If your terminfo entry for the console is correct (and has an
335 entry rs1=\Ec), then "tput reset" will also work.
336
337 The user-defined mapping table can be set using mapscrn(8). The result
338 of the mapping is that if a symbol c is printed, the symbol s = map[c]
339 is sent to the video memory. The bitmap that corresponds to s is found
340 in the character ROM, and can be changed using setfont(8).
341
342 Mouse tracking
343 The mouse tracking facility is intended to return xterm(1)-compatible
344 mouse status reports. Because the console driver has no way to know
345 the device or type of the mouse, these reports are returned in the con‐
346 sole input stream only when the virtual terminal driver receives a
347 mouse update ioctl. These ioctls must be generated by a mouse-aware
348 user-mode application such as the gpm(8) daemon.
349
350 The mouse tracking escape sequences generated by xterm(1) encode
351 numeric parameters in a single character as value+040. For example,
352 '!' is 1. The screen coordinate system is 1-based.
353
354 The X10 compatibility mode sends an escape sequence on button press
355 encoding the location and the mouse button pressed. It is enabled by
356 sending ESC [ ? 9 h and disabled with ESC [ ? 9 l. On button press,
357 xterm(1) sends ESC [ M bxy (6 characters). Here b is button-1, and x
358 and y are the x and y coordinates of the mouse when the button was
359 pressed. This is the same code the kernel also produces.
360
361 Normal tracking mode (not implemented in Linux 2.0.24) sends an escape
362 sequence on both button press and release. Modifier information is
363 also sent. It is enabled by sending ESC [ ? 1000 h and disabled with
364 ESC [ ? 1000 l. On button press or release, xterm(1) sends ESC [ M
365 bxy. The low two bits of b encode button information: 0=MB1 pressed,
366 1=MB2 pressed, 2=MB3 pressed, 3=release. The upper bits encode what
367 modifiers were down when the button was pressed and are added together:
368 4=Shift, 8=Meta, 16=Control. Again x and y are the x and y coordinates
369 of the mouse event. The upper left corner is (1,1).
370
371 Comparisons with other terminals
372 Many different terminal types are described, like the Linux console, as
373 being "VT100-compatible". Here we discuss differences between the
374 Linux console and the two most important others, the DEC VT102 and
375 xterm(1).
376
377 Control-character handling
378
379 The VT102 also recognized the following control characters:
380
381 NUL (0x00) was ignored;
382
383 ENQ (0x05) triggered an answerback message;
384
385 DC1 (0x11, ^Q, XON) resumed transmission;
386
387 DC3 (0x13, ^S, XOFF) caused VT100 to ignore (and stop transmitting) all
388 codes except XOFF and XON.
389
390 VT100-like DC1/DC3 processing may be enabled by the terminal driver.
391
392 The xterm(1) program (in VT100 mode) recognizes the control characters
393 BEL, BS, HT, LF, VT, FF, CR, SO, SI, ESC.
394
395 Escape sequences
396
397 VT100 console sequences not implemented on the Linux console:
398
399 ESC N SS2 Single shift 2. (Select G2 character set for the next
400 character only.)
401 ESC O SS3 Single shift 3. (Select G3 character set for the next
402 character only.)
403 ESC P DCS Device control string (ended by ESC \)
404 ESC X SOS Start of string.
405 ESC ^ PM Privacy message (ended by ESC \)
406 ESC \ ST String terminator
407 ESC * ... Designate G2 character set
408 ESC + ... Designate G3 character set
409
410 The program xterm(1) (in VT100 mode) recognizes ESC c, ESC # 8, ESC >,
411 ESC =, ESC D, ESC E, ESC H, ESC M, ESC N, ESC O, ESC P ... ESC \, ESC Z
412 (it answers ESC [ ? 1 ; 2 c, "I am a VT100 with advanced video option")
413 and ESC ^ ... ESC \ with the same meanings as indicated above. It
414 accepts ESC (, ESC ), ESC *, ESC + followed by 0, A, B for the DEC
415 special character and line drawing set, UK, and US-ASCII, respectively.
416
417 The user can configure xterm(1) to respond to VT220-specific control
418 sequences, and it will identify itself as a VT52, VT100, and up depend‐
419 ing on the way it is configured and initialized.
420
421 It accepts ESC ] (OSC) for the setting of certain resources. In addi‐
422 tion to the ECMA-48 string terminator (ST), xterm(1) accepts a BEL to
423 terminate an OSC string. These are a few of the OSC control sequences
424 recognized by xterm(1):
425
426 ESC ] 0 ; txt ST Set icon name and window title to txt.
427 ESC ] 1 ; txt ST Set icon name to txt.
428 ESC ] 2 ; txt ST Set window title to txt.
429 ESC ] 4 ; num; txt ST Set ANSI color num to txt.
430 ESC ] 10 ; txt ST Set dynamic text color to txt.
431 ESC ] 4 6 ; name ST Change log file to name (normally disabled
432 by a compile-time option)
433 ESC ] 5 0 ; fn ST Set font to fn.
434
435 It recognizes the following with slightly modified meaning (saving more
436 state, behaving closer to VT100/VT220):
437
438 ESC 7 DECSC Save cursor
439 ESC 8 DECRC Restore cursor
440
441 It also recognizes
442
443 ESC F Cursor to lower left corner of screen (if enabled by
444 xterm(1)'s hpLowerleftBugCompat resource)
445 ESC l Memory lock (per HP terminals).
446 Locks memory above the cursor.
447 ESC m Memory unlock (per HP terminals).
448 ESC n LS2 Invoke the G2 character set.
449 ESC o LS3 Invoke the G3 character set.
450 ESC | LS3R Invoke the G3 character set as GR.
451 ESC } LS2R Invoke the G2 character set as GR.
452 ESC ~ LS1R Invoke the G1 character set as GR.
453
454 It also recognizes ESC % and provides a more complete UTF-8 implementa‐
455 tion than Linux console.
456
457 CSI Sequences
458
459 Old versions of xterm(1), for example, from X11R5, interpret the blink
460 SGR as a bold SGR. Later versions which implemented ANSI colors, for
461 example, XFree86 3.1.2A in 1995, improved this by allowing the blink
462 attribute to be displayed as a color. Modern versions of xterm imple‐
463 ment blink SGR as blinking text and still allow colored text as an
464 alternate rendering of SGRs. Stock X11R6 versions did not recognize
465 the color-setting SGRs until the X11R6.8 release, which incorporated
466 XFree86 xterm. All ECMA-48 CSI sequences recognized by Linux are also
467 recognized by xterm, however xterm(1) implements several ECMA-48 and
468 DEC control sequences not recognized by Linux.
469
470 The xterm(1) program recognizes all of the DEC Private Mode sequences
471 listed above, but none of the Linux private-mode sequences. For dis‐
472 cussion of xterm(1)'s own private-mode sequences, refer to the Xterm
473 Control Sequences document by Edward Moy, Stephen Gildea, and Thomas E.
474 Dickey available with the X distribution. That document, though terse,
475 is much longer than this manual page. For a chronological overview,
476
477 ⟨http://invisible-island.net/xterm/xterm.log.html⟩
478
479 details changes to xterm.
480
481 The vttest program
482
483 ⟨http://invisible-island.net/vttest/⟩
484
485 demonstrates many of these control sequences. The xterm(1) source dis‐
486 tribution also contains sample scripts which exercise other features.
487
489 ESC 8 (DECRC) is not able to restore the character set changed with ESC
490 %.
491
493 In 2.0.23, CSI is broken, and NUL is not ignored inside escape
494 sequences.
495
496 Some older kernel versions (after 2.0) interpret 8-bit control
497 sequences. These "C1 controls" use codes between 128 and 159 to
498 replace ESC [, ESC ] and similar two-byte control sequence initiators.
499 There are fragments of that in modern kernels (either overlooked or
500 broken by changes to support UTF-8), but the implementation is incom‐
501 plete and should be regarded as unreliable.
502
503 Linux "private mode" sequences do not follow the rules in ECMA-48 for
504 private mode control sequences. In particular, those ending with ] do
505 not use a standard terminating character. The OSC (set palette)
506 sequence is a greater problem, since xterm(1) may interpret this as a
507 control sequence which requires a string terminator (ST). Unlike the
508 setterm(1) sequences which will be ignored (since they are invalid con‐
509 trol sequences), the palette sequence will make xterm(1) appear to hang
510 (though pressing the return-key will fix that). To accommodate appli‐
511 cations which have been hardcoded to use Linux control sequences, set
512 the xterm(1) resource brokenLinuxOSC to true.
513
514 An older version of this document implied that Linux recognizes the
515 ECMA-48 control sequence for invisible text. It is ignored.
516
518 console(4), console_ioctl(4), charsets(7)
519
521 This page is part of release 3.53 of the Linux man-pages project. A
522 description of the project, and information about reporting bugs, can
523 be found at http://www.kernel.org/doc/man-pages/.
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527Linux 2012-08-05 CONSOLE_CODES(4)