NAME 名稱

控制終端代碼 - Linux 控制終端轉(zhuǎn)義和控制序列  

DESCRIPTION 描述

Linux控制臺(tái)實(shí)現(xiàn)了VT102和ECMA-48/ISO 6429/ANSI X3.64終端控制的子集, 這個(gè)子集很龐大,當(dāng)然還有Linux自己私有的控制序列,以改變顏色配置,字符集映像,等等.在下面將要給出的表格中,第二列為指定的功能給出了ECMA-48 或者DEC助記符(如果是后者會(huì)在前面加有DEC前綴).沒有給出助記符的序列既不是ECMA-48也不是VT102字符.

在所有標(biāo)準(zhǔn)輸出進(jìn)程執(zhí)行完畢,并且一個(gè)字符流被送到控制臺(tái)驅(qū)動(dòng)程序準(zhǔn)備顯示出來的時(shí)候,所發(fā)生的第一件事就是將進(jìn)程使用的代碼轉(zhuǎn)換成顯示使用的代碼.

如果控制臺(tái)工作于 UTF-8 模式,那么輸入的字節(jié)會(huì)首先編碼成16位的 Unicode 代碼.如果不是UTF-8模式,那么每個(gè)字節(jié)會(huì)按照當(dāng)前的字符映射表完成轉(zhuǎn)換(轉(zhuǎn)換成Unicode編碼的值). 參看下面將要討論的 CHARACTER SETS 一章. 在一般情況下,Unicode 代碼被轉(zhuǎn)換成為存儲(chǔ)在視頻存儲(chǔ)器中的字體索引,這樣對(duì)應(yīng)的具體字符(字符存儲(chǔ)在視頻ROM中)就顯示在屏幕上了. 注意使用 Unicode 編碼允許我們同時(shí)使用 512 種不同的字體(和計(jì)算機(jī)硬件有關(guān)).

如果當(dāng)前的 Unicode 代碼是一個(gè)控制字符,或者系統(tǒng)目前正在處理一個(gè)轉(zhuǎn)義序列,處理的方式有些特別.它不會(huì)被轉(zhuǎn)換成字體索引,也不會(huì)直接顯示在屏幕上.它可能控制光標(biāo)的移動(dòng),或者實(shí)現(xiàn)其它控制功能.參看下面的 LINUX CONSOLE CONTROLS 一節(jié)所進(jìn)行的討論.

一般來說直接在程序中插入終端控制字符并不是很好.Linux 支持終端兼容的 terminfo(5) 數(shù)據(jù)庫. 除了直接插入控制和轉(zhuǎn)義序列,也可以使用象 ncurses(3), tput(1), 或者 reset(1). 這樣的顯示庫或者工具.

LINUX CONSOLE CONTROLS Linux終端控制

這一段描述了所有在Linux控制臺(tái)下使用的調(diào)用特殊功能的控制字符和轉(zhuǎn)義序列(例如.任何不在當(dāng)前光標(biāo)處插入可見字符的序列).  

Control characters 控制字符

當(dāng)一個(gè)字符在通過字符映射表轉(zhuǎn)換之前含有以下14個(gè)代碼之一的時(shí)候表明它是一個(gè)控制字符. 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). 我們可以通過設(shè)置 `顯示控制字符' 模式(見下文)以允許07,09,0b, 18,1a,7f 像普通字符一樣顯示在屏幕上.另一方面,在UTF-8模式下所有位于 00-1f之間的代碼都被認(rèn)為是控制字符,而不管是否處于 `顯示控制字符'模式.

一個(gè)控制字符會(huì)立刻生效,然后被丟棄(即使是在轉(zhuǎn)義序列中間), 之后轉(zhuǎn)義序列才繼續(xù)處理下一個(gè)字符. (在任何情況下,ESC都表示一個(gè)新的轉(zhuǎn)義序列的開始,可能導(dǎo)致 前一個(gè)序列的非正常終止,CAN和SUB 終止任何轉(zhuǎn)義序列.) 可識(shí)別的控制字符是BEL,BS,HT,LF,VT,FF,CR,SO,SI,CAN, SUB,ESC,DEL,CSI.他們的功能如下.:

BEL(0x07,^G)鈴聲;

BS(0x08,^H)后退一格(在行首不起作用);

HT(0x09,^I)跳至下一個(gè)制表位.如果后面已沒有制表位則跳至行尾;

LF(0x0A,^J),VT(0x0B,^K),FF(0x0C,^L)三者都表示換行;

CR(0x0D,^M)回車并換行;

SO(0x0E,^N)激活 G1 字符集, 如果設(shè)置了 LF/NL(新行模式)還要加上回車換行;

SI(0x0F,^O)激活 G0 字符集;

CAN(0x18,^X),SUB(0x1A,^Z)兩者都表示中斷轉(zhuǎn)義序列;

ESC(0x1B,^[)開始一個(gè)新的轉(zhuǎn)義序列;

DEL(0x7F)忽略;

CSI(0x9B)等同于 ESC [;

ESC- but not CSI-sequences 非控制轉(zhuǎn)義序列

ECMA-48 CSI sequence ECMA-48 CSI 序列

CSI(或者 ESC [)后面跟的參數(shù)序列大部分是NPAR(16), 就是由分號(hào)隔開的十進(jìn)制數(shù).空參數(shù)或缺少的參數(shù)以0處理. 可以用一個(gè)問號(hào)代替參數(shù)序列.

在任何情況下,系統(tǒng)讀取 CSI [(或者 ESC [ [)后的單個(gè)字符, 而忽略整個(gè)序列.(用于忽略回顯功能鍵.)

CSI 序列的動(dòng)作由其最后一個(gè)字符決定.

ECMA-48 Set Graphics Rendition 設(shè)置圖形屬性

ECMA-48 SGR 序列 ESC [ <parameters> m 設(shè)置顯示屬性. 同樣的序列可以設(shè)置一個(gè)或多個(gè)屬性.

ECMA-48 Mode Switches ECMA-48模式選擇

ESC [ 3 h

DECCRM(默認(rèn)關(guān)閉): 顯示控制字符.

ESC [ 4 h

DECIM(默認(rèn)關(guān)閉): 設(shè)置插入模式.

ESC [ 20 h

LF/NL(默認(rèn)關(guān)閉): 自動(dòng)在CR后加上 LF,VT 或者 FF.

ECMA-48 狀態(tài)報(bào)告命令.

ESC [ 5 n

設(shè)備狀態(tài)報(bào)告(DSR): 以 ESC [ 0 n 應(yīng)答(終端準(zhǔn)備好).

ESC [ 6 n

光標(biāo)位置報(bào)告(CPR): 以ESC [ y ; x R 應(yīng)答, 這里 x,y 指光標(biāo)位置.

DEC Private Mode(DECSET/DECRST)sequences DEC私有模式序列.

這里給出的序列在 ECMA-48中沒有描述.我們列出了設(shè)置模式序列; 用l替換最后一個(gè)h就是重設(shè)模式序列.

ESC [ ? 1 h

DECCKM(默認(rèn)關(guān)閉): 打開時(shí)光標(biāo)鍵送出 ESC O 前綴, 而不是 ESC [.

ESC [ ? 3 h

DECCOLM(默認(rèn) = 80 行): 交替選擇 80/132 行模式.當(dāng)原顯示模式不足以滿足要求的時(shí)候,象 resizecons(8) 這樣的用戶程序會(huì)改變終端顯示卡的硬件注冊(cè).

ESC [ ? 5 h

DECSCNM(默認(rèn)關(guān)閉): 設(shè)置視頻反轉(zhuǎn)模式.

ESC [ ? 6 h

DECOM(默認(rèn)關(guān)閉): 打開時(shí),光標(biāo)位置用相對(duì)于滾動(dòng)條左上角的位置表示.

ESC [ ? 7 h

DECAWM(默認(rèn)關(guān)閉): 打開自動(dòng)換行.在這種模式下,一行中超過80列的字符將自動(dòng)換行(在DECCOLM打開時(shí)是132列).

ESC [ ? 8 h

DECARM(默認(rèn)關(guān)閉): 打開鍵盤自動(dòng)重復(fù).

ESC [ ? 9 h

X10 鼠標(biāo)報(bào)告(默認(rèn)關(guān)閉): 設(shè)置報(bào)告模式 1(或者重設(shè)為 0)- 見下文.

ESC [ ? 25 h

DECCM(默認(rèn)打開): 設(shè)置光標(biāo)可見.

ESC [ ? 1000 h

X11 鼠標(biāo)報(bào)告(默認(rèn)關(guān)閉): 設(shè)置報(bào)告模式 2(或者重設(shè)為 0)- 見下文.

Linux Console Private CSI Sequences Linux控制臺(tái)私有控制序列

下面的序列既不屬于 ECMA-48 字符也不屬于 VT102.它們只在 Linux控制臺(tái)上使用.顏色采用 SGR 參數(shù): 0 = 黑色,1 = 紅色,2 = 綠色,3 =褐色 ,4 = 藍(lán)色,5 = 洋紅,6 = 孔雀藍(lán),7 = 白色.

CHARACTER SETS 字符集

內(nèi)核可以完成以下四種字符轉(zhuǎn)換,使字符能在屏幕上顯示. a)Latin1 -> PC,b)VT100 graphics -> PC,c)PC -> PC, d)user-defined(用戶自定義).

有兩種字符集設(shè)置,以 G0 和 G1定義,當(dāng)前字符集必定是其中之一.(初始化為G0.)鍵入 ^N 使 G1 成為當(dāng)前字符集,鍵入 ^O 使 G0 成為當(dāng)前設(shè)置.

變量 G0 and G1 指向字符映射關(guān)系表,并且這種指向關(guān)系可以由用戶改變. 系統(tǒng)初始化時(shí)它們分別指向表 a)and b). 序列 ESC( B ,ESC( 0 ,ESC( U 和 ESC( K 分別使 G0 指向字符映射表
 a),b),c)和 d). 序列 ESC )B ,ESC )0 ,ESC )U 和 ESC )K 分別使 G1 指向字符映射表 a),b),c)和 d).

序列 ESC c 重置一個(gè)終端,當(dāng)屏幕顯示出現(xiàn)混亂時(shí)可以使用這個(gè)序列. 另一個(gè)序列 "echo ^V^O" 僅僅將G0設(shè)為當(dāng)前字符集,但并不保證 G0 指向映射表 a). 有的Linux發(fā)行版中提供一個(gè)叫做 reset(1) 的程序用來送出序列 "echo ^[c". 如果你的系統(tǒng)終端變量沒有錯(cuò)誤( rs1=\Ec), 那么使用"tput reset"也可以達(dá)到同樣效果.

用戶自定義映射表可以用程序 mapscrn(8). 定義.這個(gè)程序工作時(shí)會(huì)將送入的字符c通過關(guān)系式s=map[c]映射到字符s然后送入顯存.字符s所對(duì)應(yīng)的位圖放在字符ROM里面,可以使用程序 setfont(8).

來改變.

MOUSE TRACKING 鼠標(biāo)軌跡

鼠標(biāo)軌跡工具可以返回與 xterm 兼容的鼠標(biāo)狀態(tài)報(bào)告.因?yàn)榭刂婆_(tái)驅(qū)動(dòng)沒有辦法知道鼠標(biāo)類型,只有當(dāng)虛擬終端驅(qū)動(dòng)接收到鼠標(biāo)輸入輸出消息更新時(shí)才會(huì)將這些報(bào)告返回給控制臺(tái)輸入流..這些鼠標(biāo)輸入輸出消息由 gpm(8) 守護(hù)進(jìn)程產(chǎn)生.

所有鼠標(biāo)軌跡轉(zhuǎn)義序列參數(shù)由xterm 編碼成象value+040 這樣的單一字符形式的數(shù)字參數(shù).比如,`!' 編碼成 1.屏幕坐標(biāo)系統(tǒng)以'1'為基準(zhǔn).

X10 兼容模式在鼠標(biāo)鍵按下時(shí)將按下的鍵和鼠標(biāo)位置編碼后送出. ESC [ ? 9 h 允許這一動(dòng)作,ESC [ ? 9 l禁止這一動(dòng)作. 有鍵按下時(shí),xterm 送出ESC [ M bxy(6 個(gè)字符).這里 b 代表 鍵-1,而 x 和 y 是鼠標(biāo)的 x 和 y 坐標(biāo).這和內(nèi)核產(chǎn)生的序列相同.

常規(guī)的軌跡模式(Linux 2.0.24不再支持)在左右兩鍵同時(shí)按下然后釋放時(shí)送出轉(zhuǎn)義序列.組合鍵編碼也被送出.ESC [ ? 1000 h 允許這個(gè)動(dòng)作而ESC [ 1000 l 禁止這個(gè)動(dòng)作.當(dāng)有鍵按下或者釋放時(shí), xterm 送出 ESC [ M bxy.b 的低兩位對(duì)按鍵信息編碼: 0=鼠標(biāo)鍵1按下,1=鼠標(biāo)鍵2 按下,2=鼠標(biāo)鍵3 按下,3=釋放. 高位編碼代表組合鍵,和上述編碼一起送出: 4=Shift,8=Meta(Alt),16=Control(Ctrl).x 和y為發(fā)生鼠標(biāo)事件的x和y坐標(biāo).以左上角為(1,1).

和其它終端的比較

我們已經(jīng)討論了幾種終端類型,比如Linux 控制臺(tái).這類終端稱為 "VT100兼容"的終端.這里我們?cè)俳榻B其他兩種重要的終端類型: DEC VT102 和 xterm(1) 以及他們和Linux控制終端的區(qū)別.

Control-character handling 控制字符處理

vt102 也使用以下控制序列:

NUL(0x00)忽略;

ENQ(0x05)觸發(fā)應(yīng)答消息;

DC1(0x11,^Q,XON)繼續(xù)傳送;

DC3(0x13,^S,XOFF)使 vt100 忽略(并停止傳送) 除 XOFF and XON 以外的一切字符.

VT100-like DC1/DC3 進(jìn)程可以由 tty 驅(qū)動(dòng)激活.

程序 xterm (在 vt100 模式 中)使用控制序列 BEL,BS,HT,LF,VT,FF,CR,SO,SI,ESC.

Escape sequences 轉(zhuǎn)義序列

VT100 控制臺(tái)序列不完全支持Linux控制臺(tái)序列:

程序 xterm (vt100 模式)承認(rèn) ESC c,ESC # 8,ESC >,ESC =, ESC D,ESC E,ESC H,ESC M,ESC N,ESC O,ESC P ...ESC , ESC Z(以 [ ? 1 ; 2 c,`I am a vt100 with advanced video option'回應(yīng)) 以及 ESC ^ ...ESC ,意義同上. 接受 ESC(,ESC ),ESC *,ESC + 后跟 0,A,B 的字符序列,分別代表的DEC 特殊字符,畫線設(shè)置,UK 和 US ASCII碼. 接受 ESC ] 作為特定資源設(shè)置:

以下字符的含義略有不同::

它還接受以下序列:

它不識(shí)別 ESC % ...

CSI Sequences CSI 序列

程序 xterm (直到 XFree86 3.1.2G)不能識(shí)別閃爍或者不可見模式的 SGR值.X11R6 也不能識(shí)別以 SGRs 為參數(shù)設(shè)置的色彩. xterm 可以識(shí)別其他的 ECMA-48 CSI 序列,只要Linux可以識(shí)別. 反之亦然.

xterm 可以識(shí)別以上列出的所有 DEC 私有序列,但是不包括 Linux 私有模式序列. 在 Xterm Control Sequences 中有關(guān)于 xterm 的私有模式序列的討論.

document by Edward Moy and Stephen Gildea,available with the X distribution.

BUGS

在版本為 2.0.23 的內(nèi)核中,CSI 序列的識(shí)別有些問題: 不能識(shí)別轉(zhuǎn)義序列中的NUL.

參見

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

#p#

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. 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;

CR (0x0D, ^M) gives a carriage return;

SO (0x0E, ^N) activates the G1 character set, and if LF/NL (new line mode) is set also a carriage return;

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

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.

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.

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 autorepreat on.

ESC [ ? 9 h

X10 Mouse Reporting (default off): Set reporting mode to 1 (or reset to 0) - see below.

ESC [ ? 25 h

DECCM (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.

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-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.

Parameters for all mouse tracking escape sequences generated by xterm 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 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 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 vbetween the Linux console an 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 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:

The program xterm (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 USASCII, respectively. It accepts ESC ] for the setting of certain resources:

It recognizes the following with slightly modified meaning:

It also recognizes

It does not recognize ESC % ...  

CSI Sequences

The xterm program (as of XFree86 3.1.2G) does not recognize the blink or invisible-mode SGRs. Stock X11R6 versions do not recognize the color-setting SGRs. All other ECMA-48 CSI sequences recognized by Linux are also recognized by xterm, and vice-versa.

The xterm program will recognize all of the DEC Private Mode sequences listed above, but none of the Linux private-mode sequences. For discussion of xterm's own private-mode sequences, refer to the Xterm Control Sequences document by Edward Moy and Stephen Gildea, available with the X distribution.

BUGS

In 2.0.23, CSI is broken, and NUL is not ignored inside escape sequences.

SEE ALSO

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