console_codes


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 translation 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 trans-
       formed 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 Uni-
       code (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 cur-
       rently 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
       Console 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  capabili-
       ties.   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.,  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.


       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, and
              if LF/NL (new-line mode) is set also a carriage return;

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

       SO (0x0E, ^N) activates the G1 character set;

       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 pointed at by G0, G1).
       ESC 8     DECRC    Restore state most recently saved by ESC 7.
       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  (0-15),  and  rrggbb  indicates  the
                          red/green/blue  values  (0-255).   ESC  ] R: reset

       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, separated by  semi-
       colons.   An empty parameter (between semicolons or string initiator or
       terminator) is interpreted as a zero.

       param   result
       0       reset all attributes to their defaults
       1       set bold
       2       set half-bright (simulated with color on a color display)
               toggle meta flag causes the high bit of a byte to be tog-
               gled before the mapping table translation is done.
       21      set normal intensity (ECMA-48 says "doubly underlined")
       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 [ ? 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 autorepeat on.

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

       ESC [ ? 25 h
              DECTECM (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.

       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 console-screen sym-
       bols.  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), respec-
       tively.   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.
       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(1)-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 con-
       sole  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.

       The  mouse  tracking  escape  sequences  generated  by  xterm(1) 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 button 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(1) 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.  Modifier information is
       also sent.  It is enabled by sending ESC [ ? 1000 h and  disabled  with
       ESC  [  ?  1000  l.  On button press or release, xterm(1) 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=Control.  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  discuss  differences between the
       Linux console and 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 driver.

       The xterm(1) program (in VT100 mode) recognizes the control  characters
       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(1) (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
       special character and line drawing set, UK, and US-ASCII, respectively.

       The user can configure xterm(1) to respond  to  VT220-specific  control
       sequences, and it will identify itself as a VT52, VT100, and up depend-
       ing on the way it is configured and initialized.

       It accepts ESC ] (OSC) for the setting of certain resources.  In  addi-
       tion  to  the ECMA-48 string terminator (ST), xterm(1) accepts a BEL to
       terminate an OSC string.  These are a few of the OSC control  sequences
       recognized by xterm(1):

       ESC ] 0 ; txt ST        Set icon name and window title to txt.
       ESC ] 1 ; txt ST        Set icon name to txt.
       ESC ] 2 ; txt ST        Set window title to txt.
       ESC ] 4 ; num; txt ST   Set ANSI color num to txt.
       ESC ] 10 ; txt ST       Set dynamic text color to txt.
       ESC ] 4 6 ; name ST     Change log file to name (normally disabled
                               by a compile-time option)
       ESC ] 5 0 ; fn ST       Set font to fn.

       It recognizes the following with slightly modified meaning (saving more
       state, behaving closer to VT100/VT220):

       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
                      xterm(1)'s 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 also recognizes ESC % and provides a more complete UTF-8 implementa-
       recognized  by  xterm,  however xterm(1) implements several ECMA-48 and
       DEC control sequences not recognized by Linux.

       The xterm(1) program recognizes all of the DEC Private  Mode  sequences
       listed  above,  but none of the Linux private-mode sequences.  For dis-
       cussion of xterm(1)'s own private-mode sequences, refer  to  the  Xterm
       Control Sequences document by Edward Moy, Stephen Gildea, and Thomas E.
       Dickey available with the X distribution.  That document, though terse,
       is much longer than this manual page.  For a chronological overview,

           http://invisible-island.net/xterm/xterm.log.html

       details changes to xterm.

       The vttest program

           http://invisible-island.net/vttest/

       demonstrates many of these control sequences.  The xterm(1) source dis-
       tribution also contains sample scripts which exercise other features.

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

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

       Some  older  kernel  versions  (after  2.0)  interpret  8-bit   control
       sequences.   These  "C1  controls"  use  codes  between  128 and 159 to
       replace ESC [, ESC ] and similar two-byte control sequence  initiators.
       There  are  fragments  of  that in modern kernels (either overlooked or
       broken by changes to support UTF-8), but the implementation  is  incom-
       plete and should be regarded as unreliable.

       Linux  "private  mode" sequences do not follow the rules in ECMA-48 for
       private mode control sequences.  In particular, those ending with ]  do
       not  use  a  standard  terminating  character.   The  OSC (set palette)
       sequence is a greater problem, since xterm(1) may interpret this  as  a
       control  sequence  which requires a string terminator (ST).  Unlike the
       setterm(1) sequences which will be ignored (since they are invalid con-
       trol sequences), the palette sequence will make xterm(1) appear to hang
       (though pressing the return-key will fix that).  To accommodate  appli-
       cations  which  have been hardcoded to use Linux control sequences, set
       the xterm(1) resource brokenLinuxOSC to true.

       An older version of this document implied  that  Linux  recognizes  the
       ECMA-48 control sequence for invisible text.  It is ignored.

SEE ALSO
       console(4), console_ioctl(4), charsets(7)

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