# console_codes

## 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 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 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 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 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.
                         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 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
                      (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 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 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.  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
           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 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 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
                             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**(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 initialized.
    
           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 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.
           ESC }   LS2R   Invoke the G2 character set as GR.
           ESC ~   LS1R   Invoke the G1 character set as GR.
    
           It also recognizes ESC % and provides a more complete UTF-8
           implementation than Linux console.
    
           **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 release, 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
           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 discussion 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
           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 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 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)
           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.
    


* * *