Man Pages

console_codes(4) - phpMan console_codes(4) - phpMan

Command: man perldoc info search(apropos)  


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.  Other-
       wise  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 trig-
       ger 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 recog-
       nized 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.
       K   EL        Erase line (default: from cursor to end of line).
                     ESC [ 1 K: erase from start of line to cursor.
                     ESC [ 2 K: erase whole line.
       L   IL        Insert the indicated # of blank lines.
       M   DL        Delete the indicated # of lines.
       P   DCH       Delete the indicated # of characters on the current line.
       X   ECH       Erase the indicated # of characters on the current line.
       a   HPR       Move cursor right the indicated # of columns.
       c   DA        Answer ESC [ ? 6 c: "I am a VT102".
       d   VPA       Move cursor to the indicated row, current column.
       e   VPR       Move cursor down the indicated # of rows.
       f   HVP       Move cursor to the indicated row, column.
       g   TBC       Without parameter: clear tab stop at the current position.
                     ESC [ 3 g: delete all tab stops.
       h   SM        Set Mode (see below).
       l   RM        Reset Mode (see below).
       m   SGR       Set attributes (see below).
       n   DSR       Status report (see below).
       q   DECLL     Set keyboard LEDs.
                     ESC [ 0 q: clear all LEDs
                     ESC [ 1 q: set Scroll Lock LED
                     ESC [ 2 q: set Num Lock LED
                     ESC [ 3 q: set Caps Lock LED
       r   DECSTBM   Set scrolling region; parameters are top and bottom row.
       s   ?         Save cursor location.
       u   ?         Restore cursor location.
       `   HPA       Move cursor to indicated column in current row.

       ECMA-48 Set Graphics Rendition

       The ECMA-48 SGR sequence ESC [ parameters m sets display attributes.  Several attributes can be set in the same
       sequence,  separated  by 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 tog-
               gle 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 tog-
               gled before the mapping table translation is done.
       21      set normal intensity (ECMA-48 says "doubly underlined")
       22      set normal intensity
       24      underline off
       25      blink off
       27      reverse video off
       30      set black foreground
       31      set red foreground
       32      set green foreground
       33      set brown foreground
       34      set blue foreground
       35      set magenta foreground
       36      set cyan foreground
       37      set white foreground

       38      set underscore on, set default foreground color
       39      set underscore off, set default foreground color
       40      set black background
       41      set red background
       42      set green background
       43      set brown background
       44      set blue background
       45      set magenta background
       46      set cyan background
       47      set white background
       49      set default background color

       ECMA-48 Mode Switches

       ESC [ 3 h
              DECCRM (default off): Display control chars.

       ESC [ 4 h
              DECIM (default off): Set insert mode.

       ESC [ 20 h
              LF/NL (default off): Automatically follow echo of LF, VT or FF with CR.

       ECMA-48 Status Report Commands

       ESC [ 5 n
              Device status report (DSR): Answer is ESC [ 0 n (Terminal OK).

       ESC [ 6 n
              Cursor position report (CPR): Answer is ESC [ y ; x R, where x,y is the cursor location.

       DEC Private Mode (DECSET/DECRST) sequences

       These  are  not described in ECMA-48.  We list the Set Mode sequences; the Reset Mode sequences are obtained by
       replacing the final 'h' by 'l'.

       ESC [ ? 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 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 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  con-
       sole 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 informa-
       tion: 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 dis-
       cuss differences between the Linux console and the two most important others, the DEC VT102 and xterm(1).

       Control-character handling

       The VT102 also recognized the following control characters:

       NUL (0x00) was ignored;

       ENQ (0x05) triggered an answerback message;

       DC1 (0x11, ^Q, XON) resumed transmission;

       DC3 (0x13, ^S, XOFF) caused VT100 to ignore (and stop transmitting) all codes except XOFF and XON.

       VT100-like DC1/DC3 processing may be enabled by the tty driver.

       The  xterm(1)  program  (in  VT100 mode) recognizes the control characters 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 recog-
       nized 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 pri-
       vate-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 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  frag-
       ments  of that in modern kernels (either overlooked or broken by changes to support UTF-8), but the implementa-
       tion 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  par-
       ticular,  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 accommo-
       date  applications  which have been hardcoded to use Linux control sequences, set the xterm(1) resource broken-
       LinuxOSC to true.

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

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

COLOPHON
       This  page  is part of release 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-01-01                  CONSOLE_CODES(4)