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

NAME
       console_codes - Linux console escape and control sequences

DESCRIPTION
       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 trans-
       lation from the code used for processing to the code  used
       for printing.

       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
       simultaneously.

       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
       movement or other control functions.  See the  LINUX  CON-
       SOLE CONTROLS section below for discussion.

       It  is  generally  not good practice to hard-wire terminal
       controls 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).

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

   Control characters
       A  character is a control character if (before transforma-
       tion 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 charac-
       ters, regardless of any `display control characters' mode.

       If we have a control character, it is acted  upon  immedi-
       ately  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,
       possibly aborting a previous unfinished one, and  CAN  and
       SUB  abort  any  escape sequence.)  The recognized control
       characters 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
              beginning 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
              linefeed;

       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
              sequences;

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

       DEL (0x7F) is ignored;

       CSI (0x9B) is equivalent to ESC [.

   ESC- but not CSI-sequences
       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 defining G0 character set
       ESC ( B               Select default (ISO 8859-1 mapping)
       ESC ( 0               Select vt100 graphics mapping
       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
                          (followed 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 indicates
                          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
       semicolons. An empty or absent parameter is taken to be 0.
       The  sequence  of  parameters  may be preceded by a single
       question mark.

       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
       character.

       @   ICH       Insert the indicated # of blank characters.
       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
       sequence.

       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 foreground
       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 background
       47    set white background
       49    set default background color

   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
              (Terminal 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
       replacing 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
              resizecons(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
              region.

       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.  Col-
       ors are in SGR parameters: 0 = black, 1 = red, 2 =  green,
       3 = brown, 4 = blue, 5 = magenta, 6 = cyan, 7 = white.

       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.

CHARACTER SETS
       The  kernel  knows about 4 translations of bytes into con-
       sole-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
       current.

       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 distribu-
       tions there is a program reset(1)  that  just  does  "echo
       ^[c".   If  your terminfo 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 map-
       scrn(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 bitmap that corresponds to s is found  in  the
       character ROM, and can be changed using setfont(8).

MOUSE TRACKING
       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 gener-
       ated by xterm encode numeric parameters in a single  char-
       acter  as  value+040.   For example, `!' is 1.  The screen
       coordinate system is 1-based.

       The X10 compatibility mode sends  an  escape  sequence  on
       button  press  encoding  the location and the mouse button
       pressed.  It is enabled by sending ESC [ ? 9  h  and  dis-
       abled  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  pro-
       duces.

       Normal  tracking  mode  (not  implemented in Linux 2.0.24)
       sends an escape sequence on both button press and release.
       Modifier information is also sent.  It is enabled by send-
       ing 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  modifiers  were  down  when  the  button  was
       pressed  and  are added together: 4=Shift, 8=Meta, 16=Con-
       trol.  Again x and y are the x and y  coordinates  of  the
       mouse event.  The upper left corner is (1,1).

COMPARISONS WITH OTHER TERMINALS
       Many  different  terminal  types  are  described, like the
       Linux console, as being `VT100-compatible'.  Here we  dis-
       cuss  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  charac-
       ters:

       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
       driver.

       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-
       sole:

       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 control 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, ESC >, ESC =, ESC D, ESC E, ESC H, ESC M, ESC N, ESC O,
       ESC  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  spe-
       cial  character  and  line  drawing  set, UK, and USASCII,
       respectively.  It accepts ESC ] for the setting of certain
       resources:

       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 mean-
       ing:

       ESC 7  DECSC   Save cursor
       ESC 8  DECRC   Restore cursor

       It also recognizes

       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  recog-
       nize  the  blink  or invisible-mode SGRs. Stock X11R6 ver-
       sions do not recognize the color-setting SGRs.  All  other
       ECMA-48  CSI sequences recognized by Linux are also recog-
       nized by xterm, and vice-versa.

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

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

SEE ALSO
       console(4), console_ioctl(4), charsets(4)

Linux                    October 31, 1996                       1