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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  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 transformed according to the current mapping  table
       (which  translates  it to a Unicode value).  See the CHARACTER SETS section below for dis-
       cussion.

       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 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 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. 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 ta-
       ble) 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 dis-
       played  as  glyphs.  On the other hand, in UTF-8 mode all codes 00-1f are regarded as con-
       trol 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 charac-
       ter.  (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 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 palette

   ECMA-48 CSI sequences
       CSI  (or ESC [) is followed by a sequence of parameters, at most NPAR (16), that are deci-
       mal 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 cor-
	      ner 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.  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 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 cur-
       rent.

       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),  respec-
       tively.	 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  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 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  set-
       font(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 generated by xterm encode numeric
       parameters in a single character as value+040.  For example, `!' is 1.  The screen coordi-
       nate 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 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 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-com-
       patible'.  Here we discuss differences vbetween the Linux console an the two  most  impor-
       tant 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 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 console:

       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  special
       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 meaning:

       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 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 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(7)

Linux					    1996-10-31				 CONSOLE_CODES(4)
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