NAME | DESCRIPTION | NOTES | BUGS | SEE ALSO | COLOPHON

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

NAME         top

       console_codes - Linux console escape and control sequences

DESCRIPTION         top

       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,
       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) 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
                          palette

       ECMA-48 CSI sequences

       CSI (or ESC [) is followed by a sequence of parameters, at most NPAR
       (16), that are decimal numbers separated by semicolons.  An empty or
       absent parameter is taken to be 0.  The sequence of parameters may be
       preceded by a single question mark.

       However, after CSI [ (or ESC [ [) a single character is read and this
       entire sequence is ignored.  (The idea is to ignore an echoed
       function key.)

       The action of a CSI sequence is determined by its final character.

       @   ICH       Insert the indicated # of blank characters.
       A   CUU       Move cursor up the indicated # of rows.
       B   CUD       Move cursor down the indicated # of rows.
       C   CUF       Move cursor right the indicated # of columns.
       D   CUB       Move cursor left the indicated # of columns.
       E   CNL       Move cursor down the indicated # of rows, to column 1.
       F   CPL       Move cursor up the indicated # of rows, to column 1.
       G   CHA       Move cursor to indicated column in current row.
       H   CUP       Move cursor to the indicated row, column (origin at 1,1).
       J   ED        Erase display (default: from cursor to end of display).
                     ESC [ 1 J: erase from start to cursor.
                     ESC [ 2 J: erase whole display.
                     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 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
       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)

       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 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 [ ? 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.

       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 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 fea‐
       tures.

NOTES         top

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

BUGS         top

       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 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.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 3.71 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux                            2012-08-05                 CONSOLE_CODES(4)