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[thirdparty/man-pages.git] / man4 / console_codes.4

.\" Copyright (c) 1996 Andries Brouwer <aeb@cwi.nl>, Mon Oct 31 22:13:04 1996
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" This is combined from many sources.
.\" For Linux, the definitive source is of course console.c.
.\" About vt100-like escape sequences in general there are
.\" the ISO 6429 and ISO 2022 norms, the descriptions of
.\" an actual vt100, and the xterm docs (ctlseqs.ms).
.\" Substantial portions of this text are derived from a write-up
.\" by Eric S. Raymond <esr@thyrsus.com>.
.\"
.\" Tiny correction, aeb, 961107.
.\"
.\" 2006-05-27, Several corrections - Thomas E. Dickey
.\"
.TH CONSOLE_CODES 4 2021-03-22 "Linux man-pages (unreleased)"
.SH NAME
console_codes \- Linux console escape and control sequences
.SH 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, 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.
.PP
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.
.PP
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 \fBCharacter Sets\fP section below for discussion.
.PP
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.
.PP
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 \fBLinux Console Controls\fP section below for discussion.
.PP
It is generally not good practice to hard-wire terminal controls into
programs.
Linux supports a
.BR 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
.BR ncurses (3),
.BR tput (1),
or
.BR reset (1).
.SS 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.
.PP
.B "Control characters"
.PP
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\(en1f are regarded
as control characters, regardless of any "display control characters"
mode.
.PP
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:
.TP
BEL (0x07, \fB\(haG\fP)
beeps;
.TP
BS (0x08, \fB\(haH\fP)
backspaces one column
(but not past the beginning of the line);
.TP
HT (0x09, \fB\(haI\fP)
goes to the next tab stop or to the end of the line
if there is no earlier tab stop;
.TP
LF (0x0A, \fB\(haJ\fP)
.TQ
VT (0x0B, \fB\(haK\fP)
.TQ
FF (0x0C, \fB\(haL\fP)
all give a linefeed,
and if LF/NL (new-line mode) is set also a carriage return;
.TP
CR (0x0D, \fB\(haM\fP)
gives a carriage return;
.TP
SO (0x0E, \fB\(haN\fP)
activates the G1 character set;
.TP
SI (0x0F, \fB\(haO\fP)
activates the G0 character set;
.TP
CAN (0x18, \fB\(haX\fP)
.TQ
SUB (0x1A, \fB\(haZ\fP)
abort escape sequences;
.TP
ESC (0x1B, \fB\(ha[\fP)
starts an escape sequence;
.TP
DEL (0x7F)
is ignored;
.TP
CSI (0x9B)
is equivalent to ESC [.
.PP
.B "ESC- but not CSI-sequences"
.ad l
.TS
l l lx.
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	T{
DEC private identification. The kernel
returns the string  ESC [ ? 6 c, claiming
that it is a VT102.
T}
ESC 7	DECSC	T{
Save current state (cursor coordinates,
attributes, character sets pointed at by G0, G1).
T}
ESC 8	DECRC	T{
Restore state most recently saved by ESC 7.
T}
ESC %		Start sequence selecting character set
ESC % @		\0\0\0Select default (ISO 646 / ISO 8859-1)
ESC % G		\0\0\0Select UTF-8
ESC % 8		\0\0\0Select UTF-8 (obsolete)
ESC # 8	DECALN	T{
DEC screen alignment test \- fill screen with E's.
T}
ESC (		T{
Start sequence defining G0 character set
(followed by one of B, 0, U, K, as below)
T}
ESC ( B		T{
Select default (ISO 8859-1 mapping).
T}
ESC ( 0		T{
Select VT100 graphics mapping.
T}
ESC ( U		T{
Select null mapping \- straight to character ROM.
T}
ESC ( K		T{
Select user mapping \- the map that is loaded by the utility \fBmapscrn\fP(8).
T}
ESC )		T{
Start sequence defining G1 (followed by one of B, 0, U, K, as above).
T}
ESC >	DECPNM	Set numeric keypad mode
ESC =	DECPAM	Set application keypad mode
ESC ]	OSC	T{
Operating System Command prefix.
T}
ESC ] R		Reset palette.
ESC ] P		T{
Set palette, with parameter given in 7 hexadecimal digits \fInrrggbb\fP after
the final P. Here \fIn\fP is the color (0\(en15), and \fIrrggbb\fP indicates
the red/green/blue values (0\(en255).
T}
.TE
.ad
.PP
.B "ECMA-48 CSI sequences"
.PP
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.
.PP
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.)
.PP
The action of a CSI sequence is determined by its final character.
.ad l
.TS
l l lx.
@	ICH	T{
Insert the indicated # of blank characters.
T}
A	CUU	T{
Move cursor up the indicated # of rows.
T}
B	CUD	T{
Move cursor down the indicated # of rows.
T}
C	CUF	T{
Move cursor right the indicated # of columns.
T}
D	CUB	T{
Move cursor left the indicated # of columns.
T}
E	CNL	T{
Move cursor down the indicated # of rows, to column 1.
T}
F	CPL	T{
Move cursor up the indicated # of rows, to column 1.
T}
G	CHA	T{
Move cursor to indicated column in current row.
T}
H	CUP	T{
Move cursor to the indicated row, column (origin at 1,1).
T}
J	ED	T{
Erase display (default: from cursor to end of display).
T}
		T{
ESC [ 1 J: erase from start to cursor.
T}
		T{
ESC [ 2 J: erase whole display.
T}
		T{
ESC [ 3 J: erase whole display including scroll-back
buffer (since Linux 3.0).
T}
.\" ESC [ 3 J: commit f8df13e0a901fe55631fed66562369b4dba40f8b
K	EL	T{
Erase line (default: from cursor to end of line).
T}
		T{
ESC [ 1 K: erase from start of line to cursor.
T}
		T{
ESC [ 2 K: erase whole line.
T}
L	IL	T{
Insert the indicated # of blank lines.
T}
M	DL	T{
Delete the indicated # of lines.
T}
P	DCH	T{
Delete the indicated # of characters on current line.
T}
X	ECH	T{
Erase the indicated # of characters on current line.
T}
a	HPR	T{
Move cursor right the indicated # of columns.
T}
c	DA	T{
Answer ESC [ ? 6 c: "I am a VT102".
T}
d	VPA	T{
Move cursor to the indicated row, current column.
T}
e	VPR	T{
Move cursor down the indicated # of rows.
T}
f	HVP	T{
Move cursor to the indicated row, column.
T}
g	TBC	T{
Without parameter: clear tab stop at current position.
T}
		T{
ESC [ 3 g: delete all tab stops.
T}
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	T{
Set scrolling region; parameters are top and bottom row.
T}
s	?	Save cursor location.
u	?	Restore cursor location.
\`	HPA	T{
Move cursor to indicated column in current row.
T}
.TE
.ad
.PP
.B ECMA-48 Select Graphic Rendition
.PP
The ECMA-48 SGR sequence ESC [ \fIparameters\fP 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.
.ad l
.TS
l lx.
param	result
0	T{
reset all attributes to their defaults
T}
1	set bold
2	T{
set half-bright (simulated with color on a color display)
T}
3	set italic (since Linux 2.6.22; simulated with color on a color display)
4	T{
set underscore (simulated with color on a color display)
(the colors used to simulate dim or underline are set
using ESC ] ...)
T}
5	set blink
7	set reverse video
10	T{
reset selected mapping, display control flag,
and toggle meta flag (ECMA-48 says "primary font").
T}
11	T{
select null mapping, set display control flag,
reset toggle meta flag (ECMA-48 says "first alternate font").
T}
12	T{
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.
T}
21	T{
set underline; before Linux 4.17, this value
set normal intensity (as is done in many other terminals)
T}
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	T{
256/24-bit foreground color follows, shoehorned into 16 basic colors
(before Linux 3.16: set underscore on, set default foreground color)
T}
39	T{
set default foreground color
(before Linux 3.16: set underscore off, set default foreground color)
T}
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	T{
256/24-bit background color follows, shoehorned into 8 basic colors
T}
49	set default background color
90..97	T{
set foreground to bright versions of 30..37
T}
100..107	T{
set background, same as 40..47 (bright not supported)
T}
.TE
.ad
.PP
Commands 38 and 48 require further arguments:
.TS
l lx.
;5;x	T{
256 color: values 0..15 are IBGR (black, red, green, ... white),
16..231 a 6x6x6 color cube, 232..255 a grayscale ramp
T}
;2;r;g;b	T{
24-bit color, r/g/b components are in the range 0..255
T}
.TE
.PP
.B ECMA-48 Mode Switches
.TP
ESC [ 3 h
DECCRM (default off): Display control chars.
.TP
ESC [ 4 h
DECIM (default off): Set insert mode.
.TP
ESC [ 20 h
LF/NL (default off): Automatically follow echo of LF, VT, or FF with CR.
.\"
.PP
.B ECMA-48 Status Report Commands
.\"
.TP
ESC [ 5 n
Device status report (DSR): Answer is ESC [ 0 n (Terminal OK).
.TP
ESC [ 6 n
Cursor position report (CPR): Answer is ESC [ \fIy\fP ; \fIx\fP R,
where \fIx,y\fP is the cursor location.
.\"
.PP
.B DEC Private Mode (DECSET/DECRST) sequences
.PP
.\"
These are not described in ECMA-48.
We list the Set Mode sequences;
the Reset Mode sequences are obtained by replacing the final \(aqh\(aq
by \(aql\(aq.
.TP
ESC [ ? 1 h
DECCKM (default off): When set, the cursor keys send an ESC O prefix,
rather than ESC [.
.TP
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
.BR resizecons (8)
has to change the hardware registers on the console video card.
.TP
ESC [ ? 5 h
DECSCNM (default off): Set reverse-video mode.
.TP
ESC [ ? 6 h
DECOM (default off): When set, cursor addressing is relative to
the upper left corner of the scrolling region.
.TP
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.
.TP
ESC [ ? 8 h
DECARM (default on): Set keyboard autorepeat on.
.TP
ESC [ ? 9 h
X10 Mouse Reporting (default off): Set reporting mode to 1 (or reset to
0)\(emsee below.
.TP
ESC [ ? 25 h
DECTECM (default on): Make cursor visible.
.TP
ESC [ ? 1000 h
X11 Mouse Reporting (default off): Set reporting mode to 2 (or reset
to 0)\(emsee below.
.\"
.PP
.B Linux Console Private CSI Sequences
.PP
.\"
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\(en15 = bright versions of 0\(en7.
.TS
l lx.
ESC [ 1 ; \fIn\fP ]	T{
Set color \fIn\fP as the underline color.
T}
ESC [ 2 ; \fIn\fP ]	T{
Set color \fIn\fP as the dim color.
T}
ESC [ 8 ]       	T{
Make the current color pair the default attributes.
T}
ESC [ 9 ; \fIn\fP ]	T{
Set screen blank timeout to \fIn\fP minutes.
T}
ESC [ 10 ; \fIn\fP ]	T{
Set bell frequency in Hz.
T}
ESC [ 11 ; \fIn\fP ]	T{
Set bell duration in msec.
T}
ESC [ 12 ; \fIn\fP ]	T{
Bring specified console to the front.
T}
ESC [ 13 ]      	T{
Unblank the screen.
T}
ESC [ 14 ; \fIn\fP ]   	T{
Set the VESA powerdown interval in minutes.
T}
ESC [ 15 ]	T{
Bring the previous console to the front
(since Linux 2.6.0).
T}
ESC [ 16 ; \fIn\fP ]	T{
Set the cursor blink interval in milliseconds
(since Linux 4.2).
T}
.\" commit bd63364caa8df38bad2b25b11b2a1b849475cce5
.TE
.SS 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.
.PP
There are two character sets, called G0 and G1, and one of them
is the current character set.
(Initially G0.)
Typing \fB\(haN\fP causes G1 to become current,
\fB\(haO\fP causes G0 to become current.
.PP
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.
.PP
The sequence ESC c causes a terminal reset, which is what you want if the
screen is all garbled.
The oft-advised "echo \(haV\(haO" will make only G0 current,
but there is no guarantee that G0 points at table a).
In some distributions there is a program
.BR reset (1)
that just does "echo \(ha[c".
If your terminfo entry for the console is correct
(and has an entry rs1=\eEc), then "tput reset" will also work.
.PP
The user-defined mapping table can be set using
.BR 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
.BR setfont (8).
.SS Mouse tracking
The mouse tracking facility is intended to return