NAME 名稱

控制終端代碼 - Linux 控制終端轉義和控制序列  

DESCRIPTION 描述

Linux控制臺實現了VT102和ECMA-48/ISO 6429/ANSI X3.64終端控制的子集, 這個子集很龐大,當然還有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.

在所有標準輸出進程執行完畢,并且一個字符流被送到控制臺驅動程序準備顯示出來的時候,所發生的第一件事就是將進程使用的代碼轉換成顯示使用的代碼.

如果控制臺工作于 UTF-8 模式,那么輸入的字節會首先編碼成16位的 Unicode 代碼.如果不是UTF-8模式,那么每個字節會按照當前的字符映射表完成轉換(轉換成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 代碼被轉換成為存儲在視頻存儲器中的字體索引,這樣對應的具體字符(字符存儲在視頻ROM中)就顯示在屏幕上了. 注意使用 Unicode 編碼允許我們同時使用 512 種不同的字體(和計算機硬件有關).

如果當前的 Unicode 代碼是一個控制字符,或者系統目前正在處理一個轉義序列,處理的方式有些特別.它不會被轉換成字體索引,也不會直接顯示在屏幕上.它可能控制光標的移動,或者實現其它控制功能.參看下面的 LINUX CONSOLE CONTROLS 一節所進行的討論.

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) 數據庫. 除了直接插入控制和轉義序列,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控制臺下使用的調用特殊功能的控制字符和轉義序列(例如.任何不在當前光標處插入可見字符的序列).  

Control characters 控制字符

當一個字符在通過字符映射表轉換之前含有以下14個代碼之一的時候表明它是一個控制字符. 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之間的代碼都被認為是控制字符,而不管是否處于 `顯示控制字符'模式.

一個控制字符會立刻生效,然后被丟棄(即使是在轉義序列中間), 之后轉義序列才繼續處理下一個字符. (在任何情況下,ESC都表示一個新的轉義序列的開始,可能導致 前一個序列的非正常終止,CAN和SUB 終止任何轉義序列.) 可識別的控制字符是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)兩者都表示中斷轉義序列;

ESC(0x1B,^[)開始一個新的轉義序列;

DEL(0x7F)忽略;

CSI(0x9B)等同于 ESC [;

ESC- but not CSI-sequences 非控制轉義序列

ECMA-48 CSI sequence ECMA-48 CSI 序列

CSI(或者 ESC [)后面跟的參數序列大部分是NPAR(16), 就是由分號隔開的十進制數.空參數或缺少的參數以0處理. 可以用一個問號代替參數序列.

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

CSI 序列的動作由其最后一個字符決定.

ECMA-48 Set Graphics Rendition 設置圖形屬性

ECMA-48 SGR 序列 ESC [ <parameters> m 設置顯示屬性. 同樣的序列可以設置一個或多個屬性.

ECMA-48 Mode Switches ECMA-48模式選擇

ESC [ 3 h

DECCRM(默認關閉): 顯示控制字符.

ESC [ 4 h

DECIM(默認關閉): 設置插入模式.

ESC [ 20 h

LF/NL(默認關閉): 自動在CR后加上 LF,VT 或者 FF.

ECMA-48 狀態報告命令.

ESC [ 5 n

設備狀態報告(DSR): 以 ESC [ 0 n 應答(終端準備好).

ESC [ 6 n

光標位置報告(CPR): 以ESC [ y ; x R 應答, 這里 x,y 指光標位置.

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.我們列出了設置模式序列; 用l替換最后一個h就是重設模式序列.

ESC [ ? 1 h

DECCKM(默認關閉): 打開時光標鍵送出 ESC O 前綴, 而不是 ESC [.

ESC [ ? 3 h

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

ESC [ ? 5 h

DECSCNM(默認關閉): 設置視頻反轉模式.

ESC [ ? 6 h

DECOM(默認關閉): 打開時,光標位置用相對于滾動條左上角的位置表示.

ESC [ ? 7 h

DECAWM(默認關閉): 打開自動換行.在這種模式下,一行中超過80列的字符將自動換行(在DECCOLM打開時是132列).

ESC [ ? 8 h

DECARM(默認關閉): 打開鍵盤自動重復.

ESC [ ? 9 h

X10 鼠標報告(默認關閉): 設置報告模式 1(或者重設為 0)- 見下文.

ESC [ ? 25 h

DECCM(默認打開): 設置光標可見.

ESC [ ? 1000 h

X11 鼠標報告(默認關閉): 設置報告模式 2(或者重設為 0)- 見下文.

Linux Console Private CSI Sequences Linux控制臺私有控制序列

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

CHARACTER SETS 字符集

內核可以完成以下四種字符轉換,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).

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

變量 G0 and G1 指向字符映射關系表,并且這種指向關系可以由用戶改變. 系統初始化時它們分別指向表 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 重置一個終端,當屏幕顯示出現混亂時可以使用這個序列. 另一個序列 "echo ^V^O" 僅僅將G0設為當前字符集,但并不保證 G0 指向映射表 a). 有的Linux發行版中提供一個叫做 reset(1) 的程序用來送出序列 "echo ^[c". 如果你的系統終端變量沒有錯誤( rs1=\Ec), 那么使用"tput reset"也可以達到同樣效果.

用戶自定義映射表可以用程序 mapscrn(8). 定義.這個程序工作時會將送入的字符c通過關系式s=map[c]映射到字符s然后送入顯存.字符s所對應的位圖放在字符ROM里面,可以使用程序 setfont(8).

來改變.

MOUSE TRACKING 鼠標軌跡

鼠標軌跡工具可以返回與 xterm 兼容的鼠標狀態報告.因為控制臺驅動沒有辦法知道鼠標類型,只有當虛擬終端驅動接收到鼠標輸入輸出消息更新時才會將這些報告返回給控制臺輸入流..這些鼠標輸入輸出消息由 gpm(8) 守護進程產生.

所有鼠標軌跡轉義序列參數由xterm 編碼成象value+040 這樣的單一字符形式的數字參數.比如,`!' 編碼成 1.屏幕坐標系統以'1'為基準.

X10 兼容模式在鼠標鍵按下時將按下的鍵和鼠標位置編碼后送出. ESC [ ? 9 h 允許這一動作,ESC [ ? 9 l禁止這一動作. 有鍵按下時,xterm 送出ESC [ M bxy(6 個字符).這里 b 代表 鍵-1,而 x 和 y 是鼠標的 x 和 y 坐標.這和內核產生的序列相同.

常規的軌跡模式(Linux 2.0.24不再支持)在左右兩鍵同時按下然后釋放時送出轉義序列.組合鍵編碼也被送出.ESC [ ? 1000 h 允許這個動作而ESC [ 1000 l 禁止這個動作.當有鍵按下或者釋放時, xterm 送出 ESC [ M bxy.b 的低兩位對按鍵信息編碼: 0=鼠標鍵1按下,1=鼠標鍵2 按下,2=鼠標鍵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為發生鼠標事件的x和y坐標.以左上角為(1,1).

和其它終端的比較

我們已經討論了幾種終端類型,比如Linux 控制臺.這類終端稱為 "VT100兼容"的終端.這里我們再介紹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)觸發應答消息;

DC1(0x11,^Q,XON)繼續傳送;

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 進程可以由 tty 驅動激活.

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 轉義序列

VT100 控制臺序列不完全支持Linux控制臺序列:

程序 xterm (vt100 模式)承認 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) 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,畫線設置,UK 和 US ASCII碼. 接受 ESC ] 作為特定資源設置:

以下字符的含義略有不同::

它還接受以下序列:

它不識別 ESC % ...

CSI Sequences CSI 序列

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

xterm 可以識別以上列出的所有 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 的內核中,CSI 序列的識別有些問題: 不能識別轉義序列中的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)