man > CONSOLE_CODES(4)

console_codes(4)                      Kernel Interfaces 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/IEC 6429 / ANSI
       X3.64 terminal controls, plus certain private-mode sequences for changing the color  palette,
       character-set mapping, and so on.  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 Uni‐
       code  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  discus‐
       sion.

       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 differ‐
       ent 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 sup‐
       ports 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  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, 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)
       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)
       SUB (0x1A, ^Z)
              abort 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 %              Start sequence selecting character set
       ESC % @               Select default (ISO/IEC 646 / ISO/IEC 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 (followed by one of B, 0, U, K,
                          as below)
       ESC ( B            Select default (ISO/IEC 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      Operating System Command prefix.
       ESC ] R            Reset palette.
       ESC ] P            Set palette, with parameter given in 7 hexadecimal digits nrrggbb after
                          the final P. Here n is the color (0–15), and rrggbb indicates the
                          red/green/blue values (0–255).

       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 se‐
       quence 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  ig‐
       nored.  (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.
                     ESC [ 3 J: erase whole display including scroll-back buffer (since Linux 3.0).
       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 current line.
       X   ECH       Erase the indicated # of characters on 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 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 Select Graphic Rendition

       The  ECMA-48 SGR sequence ESC [ parameters m sets display attributes.  Several attributes can
       be set in the same sequence, separated by semicolons.  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)
       3          set italic (since Linux 2.6.22; simulated with color on a color display)
       4          set underscore (simulated with color on a color display) (the colors used to simu‐
                  late 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 (ECMA-48 says
                  "primary font").
       11         select null mapping, set display control flag, reset toggle meta flag (ECMA-48
                  says "first alternate font").
       12         select null mapping, set display control flag, set toggle meta flag (ECMA-48 says
                  "second alternate font").  The toggle meta flag causes the high bit of a byte to
                  be toggled before the mapping table translation is done.
       21         set underline; before Linux 4.17, this value set normal intensity (as is done in
                  many other terminals)
       22         set normal intensity
       23         italic off (since Linux 2.6.22)
       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         256/24-bit foreground color follows, shoehorned into 16 basic colors (before Linux
                  3.16: set underscore on, set default foreground color)
       39         set default foreground color (before Linux 3.16: 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
       48         256/24-bit background color follows, shoehorned into 8 basic colors
       49         set default background color
       90..97     set foreground to bright versions of 30..37
       100..107   set background, same as 40..47 (bright not supported)

       Commands 38 and 48 require further arguments:
       ;5;x       256 color: values 0..15 are IBGR (black, red, green, ... white), 16..231  a  6x6x6
                  color cube, 232..255 a grayscale ramp
       ;2;r;g;b   24-bit color, r/g/b components are in the range 0..255

       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 loca‐
              tion.

       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  fol‐
              lowing 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; 8–15 = bright versions of 0–7.
       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.
       ESC [ 15 ]          Bring the previous console to the front (since Linux 2.6.0).
       ESC [ 16 ; n ]      Set the cursor blink interval in milliseconds (since Linux 4.2).

   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 current.

       These variables G0 and G1 point at a translation table, and can be changed by the user.  Ini‐
       tially 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 gar‐
       bled.  The oft-advised "echo ^V^O" will make only 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 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 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.

       The mouse tracking escape sequences generated by xterm(1) encode numeric parameters in a sin‐
       gle 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  but‐
       ton  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-compati‐
       ble".  Here we discuss differences between the Linux console and the two most important  oth‐
       ers, 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 terminal driver.

       The  xterm(1)  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 char‐
                         acter set for the next character
                         only.)
       ESC O       SS3   Single shift 3. (Select G3 char‐
                         acter 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(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 depending on the way it is configured and initial‐
       ized.

       It accepts ESC ] (OSC) for the setting of certain resources.   In  addition  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  op‐
                               tion).
       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  hpLowerleft‐
                      BugCompat 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.

       It  also  recognizes  ESC % and provides a more complete UTF-8 implementation than Linux con‐
       sole.

       CSI Sequences

       Old versions of xterm(1), for example, from X11R5, interpret the blink SGR  as  a  bold  SGR.
       Later  versions  which implemented ANSI colors, for example, XFree86 3.1.2A in 1995, improved
       this by allowing the blink attribute to be displayed as a color.  Modern  versions  of  xterm
       implement  blink  SGR as blinking text and still allow colored text as an alternate rendering
       of SGRs.  Stock X11R6 versions did not recognize the color-setting SGRs until the X11R6.8 re‐
       lease, which incorporated XFree86 xterm.  All ECMA-48 CSI sequences recognized by  Linux  are
       also  recognized  by  xterm,  however xterm(1) implements several ECMA-48 and DEC control se‐
       quences 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  discussion of xterm(1)'s own private-mode se‐
       quences, 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 distribution 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 Linux 2.0.23, CSI is broken, and NUL is not ignored inside escape sequences.

       Some older kernel versions (after Linux 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 incomplete and should be re‐
       garded 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 control sequences), the palette  sequence  will
       make  xterm(1) appear to hang (though pressing the return-key will fix that).  To accommodate
       applications which have been hardcoded to use Linux control sequences, set the  xterm(1)  re‐
       source 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
       ioctl_console(2), charsets(7)

Linux man-pages 6.7                          2024-01-28                             console_codes(4)