1CONSOLE_CODES(4)           Linux Programmer's Manual          CONSOLE_CODES(4)
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NAME

6       console_codes - Linux console escape and control sequences
7

DESCRIPTION

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.
21
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.
26
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).
44
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.
49
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:
68
69       BEL (0x07, ^G) beeps;
70
71       BS (0x08, ^H) backspaces one column (but not past the beginning of  the
72              line);
73
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;
76
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;
81
82       SO (0x0E, ^N) activates the G1 character set;
83
84       SI (0x0F, ^O) activates the G0 character set;
85
86       CAN (0x18, ^X) and SUB (0x1A, ^Z) interrupt escape sequences;
87
88       ESC (0x1B, ^[) starts an escape sequence;
89
90       DEL (0x7F) is ignored;
91
92       CSI (0x9B) is equivalent to ESC [.
93
94       ESC- but not CSI-sequences
95
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.
238
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       ESC [ 15 ]          Bring  the  previous  console  to  the front (since
314                           Linux 2.6.0).
315       ESC [ 16 ; n ]      Set  the  cursor  blink  interval  in  milliseconds
316                           (since Linux 4.2)
317
318   Character sets
319       The kernel knows about 4 translations of bytes into console-screen sym‐
320       bols.  The four tables are: a) Latin1 -> PC, b) VT100 graphics  ->  PC,
321       c) PC -> PC, d) user-defined.
322
323       There  are two character sets, called G0 and G1, and one of them is the
324       current character set.  (Initially G0.)  Typing ^N causes G1 to  become
325       current, ^O causes G0 to become current.
326
327       These  variables  G0  and  G1  point at a translation table, and can be
328       changed by the user.  Initially they point at tables a) and b), respec‐
329       tively.   The  sequences  ESC  (  B and ESC ( 0 and ESC ( U and ESC ( K
330       cause G0 to point at translation table a), b), c) and d), respectively.
331       The  sequences  ESC ) B and ESC ) 0 and ESC ) U and ESC ) K cause G1 to
332       point at translation table a), b), c) and d), respectively.
333
334       The sequence ESC c causes a terminal reset, which is what you  want  if
335       the  screen is all garbled.  The oft-advised "echo ^V^O" will make only
336       G0 current, but there is no guarantee that G0 points at table  a).   In
337       some  distributions  there  is  a program reset(1) that just does "echo
338       ^[c".  If your terminfo entry for the console is correct  (and  has  an
339       entry rs1=\Ec), then "tput reset" will also work.
340
341       The user-defined mapping table can be set using mapscrn(8).  The result
342       of the mapping is that if a symbol c is printed, the symbol s =  map[c]
343       is sent to the video memory.  The bitmap that corresponds to s is found
344       in the character ROM, and can be changed using setfont(8).
345
346   Mouse tracking
347       The mouse tracking facility is intended to  return  xterm(1)-compatible
348       mouse  status  reports.   Because the console driver has no way to know
349       the device or type of the mouse, these reports are returned in the con‐
350       sole  input  stream  only  when  the virtual terminal driver receives a
351       mouse update ioctl.  These ioctls must be generated  by  a  mouse-aware
352       user-mode application such as the gpm(8) daemon.
353
354       The  mouse  tracking  escape  sequences  generated  by  xterm(1) encode
355       numeric parameters in a single character as  value+040.   For  example,
356       '!' is 1.  The screen coordinate system is 1-based.
357
358       The  X10  compatibility  mode  sends an escape sequence on button press
359       encoding the location and the mouse button pressed.  It is  enabled  by
360       sending  ESC  [  ? 9 h and disabled with ESC [ ? 9 l.  On button press,
361       xterm(1) sends ESC [ M bxy (6 characters).  Here b is button-1,  and  x
362       and  y  are  the  x  and y coordinates of the mouse when the button was
363       pressed.  This is the same code the kernel also produces.
364
365       Normal tracking mode (not implemented in Linux 2.0.24) sends an  escape
366       sequence  on  both  button  press and release.  Modifier information is
367       also sent.  It is enabled by sending ESC [ ? 1000 h and  disabled  with
368       ESC  [  ?  1000  l.  On button press or release, xterm(1) sends ESC [ M
369       bxy.  The low two bits of b encode button information:  0=MB1  pressed,
370       1=MB2  pressed,  2=MB3  pressed, 3=release.  The upper bits encode what
371       modifiers were down when the button was pressed and are added together:
372       4=Shift, 8=Meta, 16=Control.  Again x and y are the x and y coordinates
373       of the mouse event.  The upper left corner is (1,1).
374
375   Comparisons with other terminals
376       Many different terminal types are described, like the Linux console, as
377       being  "VT100-compatible".   Here  we  discuss  differences between the
378       Linux console and the two most important  others,  the  DEC  VT102  and
379       xterm(1).
380
381       Control-character handling
382
383       The VT102 also recognized the following control characters:
384
385       NUL (0x00) was ignored;
386
387       ENQ (0x05) triggered an answerback message;
388
389       DC1 (0x11, ^Q, XON) resumed transmission;
390
391       DC3 (0x13, ^S, XOFF) caused VT100 to ignore (and stop transmitting) all
392              codes except XOFF and XON.
393
394       VT100-like DC1/DC3 processing may be enabled by the terminal driver.
395
396       The xterm(1) program (in VT100 mode) recognizes the control  characters
397       BEL, BS, HT, LF, VT, FF, CR, SO, SI, ESC.
398
399       Escape sequences
400
401       VT100 console sequences not implemented on the Linux console:
402
403       ESC N       SS2   Single shift 2. (Select G2 character set for the next
404                         character only.)
405       ESC O       SS3   Single shift 3. (Select G3 character set for the next
406                         character only.)
407       ESC P       DCS   Device control string (ended by ESC \)
408       ESC X       SOS   Start of string.
409       ESC ^       PM    Privacy message (ended by ESC \)
410       ESC \       ST    String terminator
411       ESC * ...         Designate G2 character set
412       ESC + ...         Designate G3 character set
413
414       The  program xterm(1) (in VT100 mode) recognizes ESC c, ESC # 8, ESC >,
415       ESC =, ESC D, ESC E, ESC H, ESC M, ESC N, ESC O, ESC P ... ESC \, ESC Z
416       (it answers ESC [ ? 1 ; 2 c, "I am a VT100 with advanced video option")
417       and ESC ^ ... ESC \ with the same  meanings  as  indicated  above.   It
418       accepts  ESC  (,  ESC  ), ESC *,  ESC + followed by 0, A, B for the DEC
419       special character and line drawing set, UK, and US-ASCII, respectively.
420
421       The user can configure xterm(1) to respond  to  VT220-specific  control
422       sequences, and it will identify itself as a VT52, VT100, and up depend‐
423       ing on the way it is configured and initialized.
424
425       It accepts ESC ] (OSC) for the setting of certain resources.  In  addi‐
426       tion  to  the ECMA-48 string terminator (ST), xterm(1) accepts a BEL to
427       terminate an OSC string.  These are a few of the OSC control  sequences
428       recognized by xterm(1):
429
430       ESC ] 0 ; txt ST        Set icon name and window title to txt.
431       ESC ] 1 ; txt ST        Set icon name to txt.
432       ESC ] 2 ; txt ST        Set window title to txt.
433       ESC ] 4 ; num; txt ST   Set ANSI color num to txt.
434       ESC ] 10 ; txt ST       Set dynamic text color to txt.
435       ESC ] 4 6 ; name ST     Change log file to name (normally disabled
436                               by a compile-time option)
437       ESC ] 5 0 ; fn ST       Set font to fn.
438
439       It recognizes the following with slightly modified meaning (saving more
440       state, behaving closer to VT100/VT220):
441
442       ESC 7  DECSC   Save cursor
443       ESC 8  DECRC   Restore cursor
444
445       It also recognizes
446
447       ESC F          Cursor to lower left corner of screen (if enabled by
448                      xterm(1)'s hpLowerleftBugCompat resource)
449       ESC l          Memory lock (per HP terminals).
450                      Locks memory above the cursor.
451       ESC m          Memory unlock (per HP terminals).
452       ESC n   LS2    Invoke the G2 character set.
453       ESC o   LS3    Invoke the G3 character set.
454       ESC |   LS3R   Invoke the G3 character set as GR.
455       ESC }   LS2R   Invoke the G2 character set as GR.
456       ESC ~   LS1R   Invoke the G1 character set as GR.
457
458       It also recognizes ESC % and provides a more complete UTF-8 implementa‐
459       tion than Linux console.
460
461       CSI Sequences
462
463       Old  versions of xterm(1), for example, from X11R5, interpret the blink
464       SGR as a bold SGR.  Later versions which implemented ANSI  colors,  for
465       example,  XFree86  3.1.2A  in 1995, improved this by allowing the blink
466       attribute to be displayed as a color.  Modern versions of xterm  imple‐
467       ment  blink  SGR  as  blinking  text and still allow colored text as an
468       alternate rendering of SGRs.  Stock X11R6 versions  did  not  recognize
469       the  color-setting  SGRs  until the X11R6.8 release, which incorporated
470       XFree86 xterm.  All ECMA-48 CSI sequences recognized by Linux are  also
471       recognized  by  xterm,  however xterm(1) implements several ECMA-48 and
472       DEC control sequences not recognized by Linux.
473
474       The xterm(1) program recognizes all of the DEC Private  Mode  sequences
475       listed  above,  but none of the Linux private-mode sequences.  For dis‐
476       cussion of xterm(1)'s own private-mode sequences, refer  to  the  Xterm
477       Control Sequences document by Edward Moy, Stephen Gildea, and Thomas E.
478       Dickey available with the X distribution.  That document, though terse,
479       is much longer than this manual page.  For a chronological overview,
480
481http://invisible-island.net/xterm/xterm.log.html
482
483       details changes to xterm.
484
485       The vttest program
486
487http://invisible-island.net/vttest/
488
489       demonstrates many of these control sequences.  The xterm(1) source dis‐
490       tribution also contains sample scripts which exercise other features.
491

NOTES

493       ESC 8 (DECRC) is not able to restore the character set changed with ESC
494       %.
495

BUGS

497       In  2.0.23,  CSI  is  broken,  and  NUL  is  not  ignored inside escape
498       sequences.
499
500       Some  older  kernel  versions  (after  2.0)  interpret  8-bit   control
501       sequences.   These  "C1  controls"  use  codes  between  128 and 159 to
502       replace ESC [, ESC ] and similar two-byte control sequence  initiators.
503       There  are  fragments  of  that in modern kernels (either overlooked or
504       broken by changes to support UTF-8), but the implementation  is  incom‐
505       plete and should be regarded as unreliable.
506
507       Linux  "private  mode" sequences do not follow the rules in ECMA-48 for
508       private mode control sequences.  In particular, those ending with ]  do
509       not  use  a  standard  terminating  character.   The  OSC (set palette)
510       sequence is a greater problem, since xterm(1) may interpret this  as  a
511       control  sequence  which requires a string terminator (ST).  Unlike the
512       setterm(1) sequences which will be ignored (since they are invalid con‐
513       trol sequences), the palette sequence will make xterm(1) appear to hang
514       (though pressing the return-key will fix that).  To accommodate  appli‐
515       cations  which  have been hardcoded to use Linux control sequences, set
516       the xterm(1) resource brokenLinuxOSC to true.
517
518       An older version of this document implied  that  Linux  recognizes  the
519       ECMA-48 control sequence for invisible text.  It is ignored.
520

SEE ALSO

522       ioctl_console(2), charsets(7)
523

COLOPHON

525       This  page  is  part of release 4.15 of the Linux man-pages project.  A
526       description of the project, information about reporting bugs,  and  the
527       latest     version     of     this    page,    can    be    found    at
528       https://www.kernel.org/doc/man-pages/.
529
530
531
532Linux                             2017-09-15                  CONSOLE_CODES(4)
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