console_codes - Linux console escape and control sequences


     The Linux console implements a large subset of the VT102 and
     ECMA-48/ISO  6429/ANSI X3.64 terminal controls, plus certain
     private-mode  sequences  for  changing  the  color  palette,
     character-set  mapping,  etc.   In  the tabular descriptions
     below, the second column gives ECMA-48 or DEC mnemonics (the
     latter  if  prefixed  with  DEC)  for  the  given  function.
     Sequences without a mnemonic are neither ECMA-48 nor VT102.

     After all the normal output processing has been done, and  a
     stream  of  characters  arrives  at  the  console driver for
     actual printing, the first thing that happens is a  transla-
     tion  from the code used for processing to the code used for

     If the console is in UTF-8 mode, then the incoming bytes are
     first  assembled  into 16-bit Unicode codes.  Otherwise each
     byte is transformed according to the current  mapping  table
     (which translates it to a Unicode value).  See the CHARACTER
     SETS section below for discussion.

     In the normal case, the Unicode value is converted to a font
     index,  and  this  is  stored  in  video memory, so that the
     corresponding glyph (as found in video ROM) appears  on  the
     screen.  Note that the use of Unicode (and the design of the
     PC hardware) allows us to use 512  different  glyphs  simul-

     If the current Unicode value is a control character,  or  we
     are  currently processing an escape sequence, the value will
     treated specially.  Instead of  being  turned  into  a  font
     index  and  rendered as a glyph, it may trigger cursor move-
     ment or other control functions.  See the LINUX CONSOLE CON-
     TROLS section below for discussion.

     It is generally not good practice to hard-wire terminal con-
     trols  into programs.  Linux supports a terminfo(5) database
     of  terminal  capabilities.  Rather  than  emitting  console
     escape sequences by hand, you will almost always want to use
     a  terminfo-aware  screen  library  or   utility   such   as
     ncurses(3), tput(1), or reset(1).


     This section describes all the control characters and escape
     sequences that invoke special functions (i.e. anything other
     than writing a glyph at the current cursor location) on  the
     Linux console.

  Control characters
     A character is a control character if (before transformation
     according  to  the mapping table) it has one of the 14 codes
     00 (NUL), 07 (BEL), 08 (BS), 09 (HT), 0a (LF), 0b  (VT),  0c
     (FF),  0d  (CR),  0e  (SO),  0f (SI), 18 (CAN), 1a (SUB), 1b
     (ESC), 7f (DEL).  One can set a `display control characters'
     mode  (see  below),  and  allow 07, 09, 0b, 18, 1a, 7f to be
     displayed as glyphs.  On the other hand, in UTF-8  mode  all
     codes  00-1f  are regarded as control characters, regardless
     of any `display control characters' mode.

     If we have a control character, it is acted upon immediately
     and  then  discarded  (even  in  the  middle  of  an  escape
     sequence) and the escape sequence continues  with  the  next
     character.  (However, ESC starts a new escape sequence, pos-
     sibly aborting a previous unfinished one, and  CAN  and  SUB
     abort  any escape sequence.)  The recognized control charac-
     ters are BEL, BS, HT, LF, VT, FF, CR, SO, SI, CAN, SUB, ESC,
     DEL, CSI. They do what one would expect:

     BEL (0x07, ^G) beeps;

     BS (0x08, ^H) backspaces one column (but not past the begin-
          ning of the line);

     HT (0x09, ^I) goes to the next tab stop or to the end of the
          line if there is no earlier tab stop;

     LF (0x0A, ^J), VT (0x0B, ^K) and FF (0x0C, ^L)  all  give  a

     CR (0x0D, ^M) gives a carriage return;

     SO (0x0E, ^N) activates the G1 character set, and  if  LF/NL
          (new line mode) is set also a carriage return;

     SI (0x0F, ^O) activates the G0 character set;

     CAN  (0x18,  ^X)  and  SUB  (0x1A,  ^Z)   interrupt   escape

     ESC (0x1B, ^[) starts an escape sequence;

     DEL (0x7F) is ignored;

     CSI (0x9B) is equivalent to ESC [.

  ESC- but not CSI-sequences
     l l l.  ESC c     RIS  Reset.  ESC D     IND  Linefeed.  ESC
     E     NEL  Newline.   ESC H     HTS  Set tab stop at current
     column.     ESC    M     RI   Reverse     linefeed.      ESC
     Z     DECID     DEC   private   identification.  The  kernel
               returns  the  string   ESC  [  ?  6  c,   claiming
               that  it  is  a  VT102.   ESC 7     DECSC     Save
     current  state  (cursor  coordinates,            attributes,
     character  sets).  ESC 8     DECRC     Restore most recently
     saved state.  ESC [     CSI  Control sequence introducer ESC
     %          Start  sequence  selecting  character  set  ESC %
     @           Select default (ISO 646  /  ISO  8859-1)  ESC  %
     G           Select  UTF-8  ESC  %  8           Select  UTF-8
     (obsolete) ESC # 8   DECALN    DEC screen alignment  test  -
     fill  screen with E's.  ESC (          Start sequence defin-
     ing G0 character set ESC ( B           Select  default  (ISO
     8859-1 mapping) ESC ( 0           Select vt100 graphics map-
     ping ESC ( U           Select null  mapping  -  straight  to
     character  ROM  ESC  ( K           Select user mapping - the
     map that is loaded by              the  utility  mapscrn(8).
     ESC  )          Start  sequence  defining G1           (fol-
     lowed  by  one  of   B,   0,   U,   K,   as   above).    ESC
     >     DECPNM    Set      numeric     keypad     mode     ESC
     =     DECPAM    Set    application    keypad    mode     ESC
     ]     OSC  (Should    be:    Operating    system    command)
               ESC ]  P  nrrggbb:  set  palette,  with  parameter
               given  in  7  hexadecimal digits after the final P
     :-(.            Here n is the color (0-16), and rrggbb indi-
     cates              the    red/green/blue   values   (0-255).
               ESC ] R: reset palette

  ECMA-48 CSI sequences
     CSI (or ESC [) is followed by a sequence of  parameters,  at
     most  NPAR (16), that are decimal numbers separated by semi-
     colons. An empty or absent parameter is taken to be 0.   The
     sequence  of parameters may be preceded by a single question

     However, after CSI [ (or ESC [ [) a single character is read
     and  this entire sequence is ignored. (The idea is to ignore
     an echoed function key.)

     The action of a CSI sequence  is  determined  by  its  final

     l l l.  @    ICH  Insert the indicated #  of  blank  charac-
     ters.   A    CUU  Move  cursor  up  the indicated # of rows.
     B    CUD  Move  cursor  down  the  indicated  #   of   rows.
     C    CUF  Move  cursor  right  the  indicated  # of columns.
     D    CUB  Move cursor  left  the  indicated  #  of  columns.
     E    CNL  Move  cursor  down  the  indicated  #  of rows, to
     column 1.  F    CPL  Move cursor up the indicated # of rows,
     to  column  1.  G    CHA  Move cursor to indicated column in
     current row.  H    CUP  Move cursor to  the  indicated  row,
     column  (origin  at 1,1).  J    ED   Erase display (default:
     from cursor to end of display).            ESC [ 1 J:  erase
     from  start  to  cursor.             ESC  [ 2 J: erase whole
     display.  K    EL   Erase line (default: from cursor to  end
     of  line).            ESC [ 1 K: erase from start of line to
     cursor.             ESC   [   2   K:   erase   whole   line.
     L    IL   Insert   the   indicated   #   of   blank   lines.
     M    DL   Delete the indicated # of lines.  P    DCH  Delete
     the   indicated   #  of  characters  on  the  current  line.
     X    ECH  Erase the indicated # of characters on the current
     line.   a    HPR  Move  cursor  right  the  indicated  #  of
     columns.  c    DA   Answer ESC [ ? 6  c:  `I  am  a  VT102'.
     d    VPA  Move  cursor to the indicated row, current column.
     e    VPR  Move  cursor  down  the  indicated  #   of   rows.
     f    HVP  Move   cursor   to   the  indicated  row,  column.
     g    TBC  Without parameter: clear tab stop at  the  current
     position.             ESC  [  3  g:  delete  all  tab stops.
     h    SM   Set Mode (see below).  l    RM   Reset  Mode  (see
     below).      m    SGR  Set     attributes    (see    below).
     n    DSR  Status  report  (see  below).   q    DECLL     Set
     keyboard   LEDs.             ESC  [  0  q:  clear  all  LEDs
               ESC [ 1 q: set Scroll Lock LED           ESC  [  2
     q:  set  Num Lock LED           ESC [ 3 q: set Caps Lock LED
     r    DECSTBM   Set scrolling region; parameters are top  and
     bottom     row.      s    ?    Save     cursor     location.
     u    ?    Restore cursor location.  `    HPA  Move cursor to
     indicated column in current row.

  ECMA-48 Set Graphics Rendition
     The ECMA-48 SGR sequence ESC [ <parameters> m  sets  display
     attributes.   Several  attributes  can  be  set  in the same

     l  l.   par  result  0    reset  all  attributes  to   their
     defaults  1    set bold 2    set half-bright (simulated with
     color on a color  display)  4    set  underscore  (simulated
     with  color  on  a  color  display)      (the colors used to
     simulate dim or underline are  set       using  ESC  ]  ...)
     5    set  blink  7    set  reverse video 10   reset selected
     mapping, display control flag,      and  toggle  meta  flag.
     11   select   null   mapping,   set  display  control  flag,
          reset toggle meta flag.  12   select null mapping,  set
     display control flag,      set toggle meta flag. (The toggle
     meta flag      causes the high bit of a byte to  be  toggled
          before   the   mapping   table  translation  is  done.)
     21   set normal  intensity  (this  is  not  compatible  with
     ECMA-48)   22   set   normal  intensity  24   underline  off
     25   blink off 27   reverse video off 30   set  black  fore-
     ground  31   set  red  foreground  32   set green foreground
     33   set brown foreground 34   set blue foreground  35   set
     magenta  foreground  36   set cyan foreground 37   set white
     foreground 38   set underscore on,  set  default  foreground
     color  39   set underscore off, set default foreground color
     40   set black background 41   set red  background  42   set
     green  background  43   set  brown  background 44   set blue
     background 45   set magenta background 46   set  cyan  back-
     ground 47   set white background 49   set default background

  ECMA-48 Mode Switches
     ESC [ 3 h
          DECCRM (default off): Display control chars.

     ESC [ 4 h
          DECIM (default off): Set insert mode.

     ESC [ 20 h
          LF/NL (default off): Automatically follow echo  of  LF,
          VT or FF with CR.

  ECMA-48 Status Report Commands
     ESC [ 5 n
          Device status report (DSR): Answer is ESC [ 0 n (Termi-
          nal OK).

     ESC [ 6 n
          Cursor position report (CPR): Answer is ESC [ y ; x  R,
          where x,y is the cursor location.

  DEC Private Mode (DECSET/DECRST) sequences.
     These are not described in ECMA-48.  We list  the  Set  Mode
     sequences;  the Reset Mode sequences are obtained by replac-
     ing the final `h' by `l'.

     ESC [ ? 1 h
          DECCKM (default off): When set, the cursor keys send an
          ESC O prefix, rather than ESC [.

     ESC [ ? 3 h
          DECCOLM (default off = 80  columns):  80/132  col  mode
          switch.   The  driver sources note that this alone does
          not suffice; some user-mode  utility  such  as  resize-
          cons(8)  has  to  change  the hardware registers on the
          console video card.

     ESC [ ? 5 h
          DECSCNM (default off): Set reverse-video mode.

     ESC [ ? 6 h
          DECOM (default off): When  set,  cursor  addressing  is
          relative  to  the  upper  left  corner of the scrolling

     ESC [ ? 7 h
          DECAWM (default on): Set autowrap on.  In this mode,  a
          graphic  character  emitted  after column 80 (or column
          132 of DECCOLM is on) forces a wrap to the beginning of
          the following line first.

     ESC [ ? 8 h
          DECARM (default on): Set keyboard autorepreat on.

     ESC [ ? 9 h
          X10 Mouse Reporting (default off): Set  reporting  mode
          to 1 (or reset to 0) - see below.

     ESC [ ? 25 h
          DECCM (default on): Make cursor visible.

     ESC [ ? 1000 h
          X11 Mouse Reporting (default off): Set  reporting  mode
          to 2 (or reset to 0) - see below.

  Linux Console Private CSI Sequences
     The following  sequences  are  neither  ECMA-48  nor  native
     VT102.  They are native to the Linux console driver.  Colors
     are in SGR parameters:  0 = black, 1 = red, 2 = green,  3  =
     brown, 4 = blue, 5 = magenta, 6 = cyan, 7 = white.

     l l.  ESC [ 1 ; n ]  Set color n as the underline color  ESC
     [  2  ;  n  ]  Set  color  n  as  the  dim  color  ESC [ 8 ]
         Make the current color pair the default attributes.  ESC
     [  9 ; n ]  Set screen blank timeout to n minutes.  ESC [ 10
     ; n ] Set bell frequency in Hz.  ESC [ 11  ;  n  ] Set  bell
     duration in msec.  ESC [ 12 ; n ] Bring specified console to
     the front.  ESC [ 13 ]          Unblank the screen.   ESC  [
     14 ; n ]      Set the VESA powerdown interval in minutes.


     The  kernel  knows  about  4  translations  of  bytes   into
     console-screen  symbols.   The four tables are: a) Latin1 ->
     PC,  b) VT100 graphics -> PC, c) PC -> PC, d) user-defined.

     There are two character sets, called G0 and G1, and  one  of
     them  is  the current character set. (Initially G0.)  Typing
     ^N causes G1 to become  current,  ^O  causes  G0  to  become

     These variables G0 and G1 point at a translation table,  and
     can  be  changed by the user. Initially they point at tables
     a) and b), respectively.  The sequences ESC ( B and ESC (  0
     and  ESC  (  U  and ESC ( K cause G0 to point at translation
     table a), b), c) and d), respectively.  The sequences ESC  )
     B  and  ESC ) 0 and ESC ) U and ESC ) K cause G1 to point at
     translation table a), b), c) and d), respectively.

     The sequence ESC c causes a terminal reset,  which  is  what
     you want if the screen is all garbled. The oft-advised "echo
     ^V^O" will only make G0 current, but there is  no  guarantee
     that  G0 points at table a).  In some distributions there is
     a program reset(1) that just does "echo ^[c".  If your  ter-
     minfo  entry  for  the  console is correct (and has an entry
     rs1=\Ec), then "tput reset" will also work.

     The user-defined mapping table can be set using  mapscrn(8).
     The  result of the mapping is that if a symbol c is printed,
     the symbol s = map[c] is sent to the video memory. The  bit-
     map that corresponds to s is found in the character ROM, and
     can be changed using setfont(8).


     The mouse tracking facility is  intended  to  return  xterm-
     compatible mouse status reports.  Because the console driver
     has no way to know the device or type of  the  mouse,  these
     reports  are  returned in the console input stream only when
     the virtual terminal driver receives a mouse  update  ioctl.
     These  ioctls  must  be generated by a mouse-aware user-mode
     application such as the gpm(8) daemon.

     Parameters for all mouse tracking escape sequences generated
     by  xterm encode numeric parameters in a single character as
     value+040.  For example, `!' is 1.   The  screen  coordinate
     system is 1-based.

     The X10 compatibility mode sends an escape sequence on  but-
     ton  press  encoding  the  location  and  the  mouse  button
     pressed.  It is enabled by sending ESC [ ? 9 h and  disabled
     with  ESC [ ? 9 l.  On button press, xterm sends ESC [ M bxy
     (6 characters).  Here b is button-1, and x and y are  the  x
     and  y coordinates of the mouse when the button was pressed.
     This is the same code the kernel also produces.

     Normal tracking mode (not implemented in Linux 2.0.24) sends
     an escape sequence on both button press and release.  Modif-
     ier information is also sent.  It is enabled by sending  ESC
     [  ? 1000 h and disabled with ESC [ 1000 l.  On button press
     or release, xterm sends ESC [ M bxy.  The low two bits of  b
     encode  button  information:   0=MB1 pressed, 1=MB2 pressed,
     2=MB3 pressed, 3=release.  The upper bits encode what modif-
     iers  were  down  when  the button was pressed and are added
     together: 4=Shift, 8=Meta, 16=Control.  Again x  and  y  are
     the  x and y coordinates of the mouse event.  The upper left
     corner is (1,1).


     Many different terminal types are described, like the  Linux
     console,  as  being  `VT100-compatible'.   Here  we  discuss
     differences vbetween the  Linux  console  an  the  two  most
     important others, the DEC VT102 and xterm(1).

  Control-character handling
     The vt102 also recognized the following control characters:

     NUL (0x00) was ignored;

     ENQ (0x05) triggered an answerback message;

     DC1 (0x11, ^Q, XON) resumed transmission;

     DC3 (0x13, ^S,  XOFF)  caused  vt100  to  ignore  (and  stop
          transmitting) all codes except XOFF and XON.

     VT100-like DC1/DC3 processing may  be  enabled  by  the  tty

     The xterm program (in vt100  mode)  recognizes  the  control
     characters BEL, BS, HT, LF, VT, FF, CR, SO, SI, ESC.

  Escape sequences
     VT100 console sequences not implemented on  the  Linux  con-

     l l l.  ESC N     SS2  Single shift 2. (Select G2  character
     set   for   the   next             character   only.)    ESC
     O     SS3  Single shift 3. (Select G3 character set for  the
     next            character only.)  ESC P     DCS  Device con-
     trol string (ended by ESC \) ESC X     SOS  Start of string.
     ESC   ^     PM   Privacy   message  (ended  by  ESC  \)  ESC
     \     ST   String terminator  ESC  *  ...      Designate  G2
     character set ESC + ...      Designate G3 character set

     The program xterm (in vt100 mode) recognizes ESC c, ESC # 8,
     P ... ESC , ESC Z (it answers ESC [ ? 1 ; 2 c, `I am a vt100
     with  advanced  video  option')  and ESC ^ ... ESC  with the
     same meanings as indicated above.  It accepts ESC (, ESC  ),
     ESC  *,  ESC + followed by 0, A, B for the DEC special char-
     acter and line drawing set, UK, and  USASCII,  respectively.
     It accepts ESC ] for the setting of certain resources:

     l l.  ESC ] 0 ; txt BEL   Set icon name and window title  to
     txt.   ESC  ] 1 ; txt BEL   Set icon name to txt.  ESC ] 2 ;
     txt BEL   Set window title  to  txt.   ESC  ]  4  6  ;  name
     BEL     Change log file to name (normally disabled      by a
     compile-time option) ESC ] 5 0 ; fn BEL  Set font to fn.

     It recognizes the following with slightly modified meaning:

     l l l.  ESC 7  DECSC   Save cursor  ESC  8   DECRC   Restore

     It also recognizes

     l l l.  ESC F          Cursor to lower left corner of screen
     (if  enabled by           the hpLowerleftBugCompat resource)
     ESC   l          Memory    lock    (per    HP    terminals).
               Locks    memory    above    the    cursor.     ESC
     m          Memory   unlock   (per   HP   terminals).     ESC
     n     LS2  Invoke     the    G2    character    set.     ESC
     o     LS3  Invoke    the    G3    character    set.      ESC
     |     LS3R Invoke the G3 character set as GR.            Has
     no visible effect in xterm.  ESC  }     LS2R Invoke  the  G2
     character  set  as  GR.             Has no visible effect in
     xterm.  ESC ~     LS1R Invoke the G1 character  set  as  GR.
               Has no visible effect in xterm.

     It does not recognize ESC % ...

  CSI Sequences
     The xterm program (as of XFree86 3.1.2G) does not  recognize
     the  blink  or  invisible-mode SGRs. Stock X11R6 versions do
     not recognize the color-setting SGRs.  All other ECMA-48 CSI
     sequences  recognized by Linux are also recognized by xterm,
     and vice-versa.

     The xterm program will recognize all of the DEC Private Mode
     sequences  listed  above, but none of the Linux private-mode
     sequences.   For  discussion  of  xterm's  own  private-mode
     sequences,  refer to the Xterm Control Sequences document by
     Edward Moy and Stephen Gildea, available with the X  distri-


     In 2.0.23, CSI is broken, and  NUL  is  not  ignored  inside
     escape sequences.


     console(4), console_ioctl(4), charsets(4)