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console_codes(4) Kernel Interfaces Manual console_codes(4)
console_codes - Linux console escape and control sequences
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.
ESC 8 (DECRC) is not able to restore the character set changed
with ESC %.
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.
ioctl_console(2), charsets(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
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Linux man-pages 6.9.1 2024-06-15 console_codes(4)
Pages that refer to this page: quilt(1), ioctl_console(2)
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