ANSI escape code

ANSI escape sequences are a standard for in-band signaling to control the cursor location, color, and other options on video text terminals and terminal emulators. Certain sequences of bytes, most starting with Esc and '[', are embedded into the text, which the terminal looks for and interprets as commands, not as character codes.

ANSI sequences were introduced in the 1970s to replace vendor-specific sequences and became widespread in the computer equipment market by the early 1980s. They were used in development, scientific and commercial applications and later by the nascent bulletin board systems to offer improved displays compared to earlier systems lacking cursor movement, a primary reason they became a standard adopted by all manufacturers.

Although hardware text terminals have become increasingly rare in the 21st century, the relevance of the ANSI standard persists because most terminal emulators interpret at least some of the ANSI escape sequences in output text. A notable exception was DOS and older versions of the Win32 console of Microsoft Windows.

History

Almost all manufacturers of video terminals added vendor-specific escape sequences to perform operations such as placing the cursor at arbitrary positions on the screen. One example is the VT52 terminal, which allowed the cursor to be placed at an x,y location on the screen by sending the `ESC` character, a `Y` character, and then two characters representing with numerical values equal to the x,y location plus 32 (thus starting at the ASCII space character and avoiding the control characters).

As these sequences were different for different terminals, elaborate libraries such as termcap and utilities such as tput had to be created so programs could use the same API to work with any terminal. In addition many of these terminals required sending numbers (such as row and column) as the binary values of the characters; for some programming languages, and for systems that did not use ASCII internally, it was often difficult or impossible to turn a number into the correct character.

The ANSI standard attempted to address these problems by making a command set that all terminals would use and requiring all numeric information to be transmitted as ASCII numbers. The first standard in the series was ECMA-48, adopted in 1976. It was a continuation of a series of character coding standards, the first one being ECMA-6 from 1965, a 7-bit standard from which ISO 646 originates. The name "ANSI escape sequence" dates from 1979 when ANSI adopted ANSI X3.64. The ANSI X3L2 committee collaborated with the ECMA committee TC 1 to produce nearly identical standards. These two standards were merged into an international standard, ISO 6429.[1] In 1994, ANSI withdrew its standard in favor of the international standard.

The first popular video terminal to support these sequences was the Digital VT100, introduced in 1978.[2] This model was very successful in the market, which sparked a variety of VT100 clones, among the earliest and most popular of which was the much more affordable Zenith Z-19 in 1979.[3] Others included the Qume QVT-108, Televideo TVI-970, Wyse WY-99GT as well as optional "VT100" or "VT103" or "ANSI" modes with varying degrees of compatibility on many other brands. The popularity of these gradually led to more and more software (especially bulletin board systems and other online services) assuming the escape sequences worked, leading to almost all new terminals and emulator programs supporting them.

In 1981, ANSI X3.64 was adopted for use in the US government by FIPS publication 86. Later, the US government stopped duplicating industry standards, so FIPS pub. 86 was withdrawn.[4]

ECMA-48 has been updated several times and is currently at its 5th edition, from 1991. It is also adopted by ISO and IEC as standard ISO/IEC 6429.

Platform support

Unix-like systems

Although termcap/terminfo-style libraries were primarily developed on and for Unix, since about 1984 programs running on Unix-like operating systems could almost always assume they were using a terminal or emulator that supported ANSI sequences;[citation needed] this led to widespread use of ANSI by programs running on those platforms. For instance, many games and shell scripts (see below for colored prompt examples), and utilities such as color directory listings, directly write the ANSI sequences and thus cannot be used on a terminal that does not interpret them. Many programs, including text editors such as vi and GNU Emacs, still use termcap or terminfo, or use libraries such as curses that use termcap or terminfo, and thus in theory support non-ANSI terminals, but this is so rarely tested nowadays that they are unlikely to work with those terminals.[citation needed] Terminal emulators for communicating with local programs as well as remote machines and the text system console almost always support ANSI escape codes.

DOS

MS-DOS 1.x did not support the ANSI or any other escape sequences. Only a few control characters (BEL, CR, LF, BS) were interpreted by the underlying BIOS, making it almost[nb 1] impossible to do any kind of full-screen application. Any display effects had to be done with BIOS calls, which were notoriously slow, or by directly manipulating the IBM PC hardware.

DOS 2.0 introduced the ability to add a device driver for the ANSI escape sequences – the de facto standard being ANSI.SYS, but others like ANSI.COM,[5] NANSI.SYS[6] and ANSIPLUS.EXE are used as well (these are considerably faster as they bypass the BIOS). Slowness and the fact that it was not installed by default made software rarely take advantage of it; instead, applications continued to directly manipulate the hardware to get the text display needed.[citation needed] ANSI.SYS and similar drivers continued to work in Windows 9x up to Windows Me, and in NT-derived systems for 16-bit legacy programs executing under the NTVDM.

PTS-DOS[7][8] as well as Concurrent DOS, Multiuser DOS[9] and REAL/32 have built-in support for ANSI ecape sequences (plus a number of extensions) and do not require a separate ANSI driver to be loaded.

OS/2

The ANSI command in a batch file or at the command line enables the extensions.

Atari ST

The Atari ST used the command system adapted from the VT52 with some expansions for color support,[10] rather than supporting ANSI escape codes.

AmigaOS

AmigaOS not only interprets ANSI code sequences for text output to the screen, the AmigaOS printer driver also interprets them (with extensions proprietary to AmigaOS) and translates them into the codes required for the particular printer that is actually attached.[11]

Windows

The Windows Console did not originally support ANSI escape sequences. Some replacements or additions for the console window such as JP Software's TCC (formerly 4NT), Michael J. Mefford's ANSI.COM, Jason Hood's ANSICON[12] and Maximus5's ConEmu interpreted ANSI escape sequences printed by programs. A Python package[13] internally interpreted ANSI escape sequences in text being printed, translating them to calls to manipulate the color and cursor position, to make it easier to port Python code using ANSI to Windows.

In 2016, Microsoft released the Windows 10 Version 1511 update which unexpectedly implemented support for ANSI escape sequences[14]. The change was designed to complement the Windows Subsystem for Linux, adding to the Windows Console Host used by Command Prompt support for character escape codes used by terminal-based software for Unix-like systems. This is not the default behavior and must be enabled by enabled programmatically with the Win32 API via `SetConsoleMode(handle, ENABLE_VIRTUAL_TERMINAL_PROCESSING)`.[15] This was enabled by CMD.EXE but not initially by PowerShell[16] however, Windows PowerShell 5.1 now enables this by default. The ability to make a string constant containing ESC was added in PowerShell 6 with (for example) `"`e[32m"`,[17] for PowerShell 5 you had to use `[char]0x1B+"[32m"`.

Escape sequences

Sequences have different lengths. All sequences start with `ESC` (27 / hex 0x1B), followed by a second byte in the range 0x40–0x5F (ASCII `@A–Z[\]^_`).[18]:5.3.a

The standard says that in 8-bit environments these two-byte sequences can be merged into single C1 control code in the 0x80–0x9F range.[18]:5.4.a However on modern devices those codes are often used for other purposes, such as parts of UTF-8 or for CP-1252 characters, so only the 2-byte sequence is used.

Other C0 codes besides ESC — commonly BEL, BS, CR, LF, FF, TAB, VT, SO, and SI — produce similar or identical effects to some control sequences when output.

Some ANSI escape sequences (not an exhaustive list)
Sequence C1 Name Effect
ESC N 0x8E SS2 – Single Shift Two Select a single character from one of the alternative character sets. In xterm, SS2 selects the G2 character set, and SS3 selects the G3 character set.[19]
ESC O 0x8F SS3 – Single Shift Three
ESC P 0x90 DCS – Device Control String Terminated by ST. Xterm's uses of this sequence include defining User-Defined Keys, and requesting or setting Termcap/Terminfo data.[19]
ESC [ 0x9B CSI - Control Sequence Introducer Most of the useful sequences, see next section.
ESC \ 0x9C ST – String Terminator Terminates strings in other controls.[18]:8.3.143
ESC ] 0x9D OSC – Operating System Command Starts a control string for the operating system to use, terminated by ST.[18]:8.3.89 In xterm, they may also be terminated by BEL.[19] In xterm, the window title can be set by `OSC 0;this is the window title BEL`.
ESC X 0x98 SOS – Start of String Takes an argument of a string of text, terminated by ST. The uses for these string control sequences are defined by the application[18]:8.3.2,8.3.128 or privacy discipline.[18]:8.3.94 These functions are not implemented and the arguments are ignored by xterm.[19]
ESC ^ 0x9E PM – Privacy Message
ESC _ 0x9F APC – Application Program Command
ESC c RIS – Reset to Initial State Resets the device to its original state. This may include (if applicable): reset graphic rendition, clear tabulation stops, reset to default font, and more.

Pressing special keys on the keyboard, as well as outputting many xterm CSI, DCS, or OSC sequences, often produces a CSI, DCS, or OSC sequence, sent from the terminal to the computer as though the user typed it.

CSI sequences

For CSI, or "Control Sequence Introducer" commands, the `ESC [` is followed by any number (including none) of "parameter bytes" in the range 0x30–0x3F (ASCII `0–9:;<=>?`), then by any number of "intermediate bytes" in the range 0x20–0x2F (ASCII space and `!"#\$%&'()*+,-./`), then finally by a single "final byte" in the range 0x40–0x7E (ASCII `@A–Z[\]^_`a–z{|}~`).[18]:5.4

All common sequences just use the parameters as a series of semicolon-separated numbers such as `1;2;3`. Missing numbers are treated as `0` (`1;;3` acts like the middle number is `0`, and no parameters at all in `ESC[m` acts like a `0` reset code). Some sequences (such as CUU) treat `0` as `1` in order to make missing parameters useful.[18]:F.4.2 Bytes other than digits and semicolon seem to not be used.[citation needed]

A subset of arrangements was declared "private" so that terminal manufacturers could insert their own sequences without conflicting with the standard. Sequences containing the parameter bytes `<=>?` or the final bytes 0x70–0x7E (`p–z{|}~`) are private.

The behavior of the terminal is undefined in the case where a CSI sequence contains any character outside of the range 0x20–0x7E. These illegal characters are either C0 control characters (the range 0–0x1F), DEL (0x7F), or bytes with the high bit set. Possible responses are to ignore the byte, to process it immediately, and furthermore whether to continue with the CSI sequence, to abort it immediately, or to ignore the rest of it.[citation needed]

Some ANSI control sequences (not an exhaustive list)
Code Name Effect

CSI n A CUU – Cursor Up Moves the cursor n (default `1`) cells in the given direction. If the cursor is already at the edge of the screen, this has no effect.

CSI n B CUD – Cursor Down

CSI n C CUF – Cursor Forward

CSI n D CUB – Cursor Back
CSI n E CNL – Cursor Next Line Moves cursor to beginning of the line n (default `1`) lines down. (not ANSI.SYS)
CSI n F CPL – Cursor Previous Line Moves cursor to beginning of the line n (default `1`) lines up. (not ANSI.SYS)
CSI n G CHA – Cursor Horizontal Absolute Moves the cursor to column n (default `1`). (not ANSI.SYS)

CSI n ; m H CUP – Cursor Position Moves the cursor to row n, column m. The values are 1-based, and default to `1` (top left corner) if omitted. A sequence such as `CSI ;5H` is a synonym for `CSI 1;5H` as well as `CSI 17;H` is the same as `CSI 17H` and `CSI 17;1H`

CSI n J ED – Erase in Display Clears part of the screen. If n is `0` (or missing), clear from cursor to end of screen. If n is `1`, clear from cursor to beginning of the screen. If n is `2`, clear entire screen (and moves cursor to upper left on DOS ANSI.SYS). If n is `3`, clear entire screen and delete all lines saved in the scrollback buffer (this feature was added for xterm and is supported by other terminal applications).

CSI n K EL – Erase in Line Erases part of the line. If n is `0` (or missing), clear from cursor to the end of the line. If n is `1`, clear from cursor to beginning of the line. If n is `2`, clear entire line. Cursor position does not change.

CSI n S SU – Scroll Up Scroll whole page up by n (default `1`) lines. New lines are added at the bottom. (not ANSI.SYS)

CSI n T SD – Scroll Down Scroll whole page down by n (default `1`) lines. New lines are added at the top. (not ANSI.SYS)

CSI n ; m f HVP – Horizontal Vertical Position Same as CUP
CSI n m SGR – Select Graphic Rendition Sets the appearance of the following characters, see SGR parameters below.

CSI 5i AUX Port On Enable aux serial port usually for local serial printer

CSI 4i AUX Port Off Disable aux serial port usually for local serial printer

CSI 6n DSR – Device Status Report Reports the cursor position (CPR) to the application as (as though typed at the keyboard) `ESC[n;mR`, where n is the row and m is the column.)

CSI s SCP – Save Cursor Position Saves the cursor position/state.

CSI u RCP – Restore Cursor Position Restores the cursor position/state.
Some popular private sequences
Code Effect
CSI ? 25 h DECTCEM Shows the cursor, from the VT320.
CSI ? 25 l DECTCEM Hides the cursor.
CSI ? 1049 h Enable alternative screen buffer
CSI ? 1049 l Disable alternative screen buffer
CSI ? 2004 h Turn on bracketed paste mode. Text pasted into the terminal will be surrounded by `ESC [200~` and `ESC [201~`, and characters in it should not be treated as commands (for example in Vim).[20] From Unix terminal emulators.
CSI ? 2004 l Turn off bracketed paste mode.

SGR parameters

SGR (Select Graphic Rendition) sets display attributes. Several attributes can be set in the same sequence, separated by semicolons.[21] Each display attribute remains in effect until a following occurrence of SGR resets it.[1] If no codes are given, `CSI m` is treated as `CSI 0 m` (reset / normal).

In ECMA-48 SGR is called "Select Graphic Rendition".[1] In Linux manual pages the term "Set Graphics Rendition" is used.[21]

Code Effect Note
0 Reset / Normal all attributes off
1 Bold or increased intensity
2 Faint (decreased intensity)
3 Italic Not widely supported. Sometimes treated as inverse.
4 Underline
5 Slow Blink less than 150 per minute
6 Rapid Blink MS-DOS ANSI.SYS; 150+ per minute; not widely supported
7 reverse video swap foreground and background colors
8 Conceal Not widely supported.
9 Crossed-out Characters legible, but marked for deletion.
10 Primary(default) font
11–19 Alternative font Select alternative font ${\displaystyle n-10}$
20 Fraktur Rarely supported
21 Doubly underline or Bold off Double-underline per ECMA-48.[22] See discussion
22 Normal color or intensity Neither bold nor faint
23 Not italic, not Fraktur
24 Underline off Not singly or doubly underlined
27 Inverse off
28 Reveal conceal off
29 Not crossed out
30–37 Set foreground color See color table below
38 Set foreground color Next arguments are `5;n` or `2;r;g;b`, see below
39 Default foreground color implementation defined (according to standard)
40–47 Set background color See color table below
48 Set background color Next arguments are `5;n` or `2;r;g;b`, see below
49 Default background color implementation defined (according to standard)
51 Framed
52 Encircled
53 Overlined
54 Not framed or encircled
55 Not overlined
60 ideogram underline or right side line Rarely supported
61 ideogram double underline or
double line on the right side
62 ideogram overline or left side line
63 ideogram double overline or
double line on the left side
64 ideogram stress marking
65 ideogram attributes off reset the effects of all of `60``64`
90–97 Set bright foreground color aixterm (not in standard)
100–107 Set bright background color aixterm (not in standard)

Colors

3/4 bit

The original specification only had 8 colors, and just gave them names. The SGR parameters 30-37 selected the foreground color, while 40-47 selected the background. Quite a few terminals implemented "bold" (SGR code 1) as a brighter color rather than a different font, thus providing 8 additional foreground colors. Usually you could not get these as background colors, though sometimes inverse video (SGR code 7) would allow that. Examples: to get black letters on white background use `ESC[30;47m`, to get red use `ESC[31m`, to get bright red use `ESC[1;31m`. To reset colors to their defaults, use `ESC[39;49m` (not supported on some terminals), or reset all attributes with `ESC[0m`. Later terminals added the ability to directly specify the "bright" colors with 90-97 and 100-107.

When hardware started using 8-bit DACs several pieces of software assigned 24-bit color numbers to these names. The chart below shows values sent to the DAC for some common hardware and software.[citation needed]

Name FG Code BG Code VGA[nb 2] Windows Console[nb 3] Windows PowerShell[nb 4] Windows 10 Console[nb 5]
PowerShell 6
Terminal.app PuTTY mIRC xterm X[nb 6] Ubuntu[nb 7]
Black 30 40 0,0,0 12,12,12 0,0,0 1,1,1
Red 31 41 170,0,0 128,0,0 197,15,31 194,54,33 187,0,0 127,0,0 205,0,0 255,0,0 222,56,43
Green 32 42 0,170,0 0,128,0 19,161,14 37,188,36 0,187,0 0,147,0 0,205,0 0,255,0 57,181,74
Yellow 33 43 170,85,0[nb 8] 128,128,0 238,237,240 193,156,0 173,173,39 187,187,0 252,127,0 205,205,0 255,255,0 255,199,6
Blue 34 44 0,0,170 0,0,128 0,55,218 73,46,225 0,0,187 0,0,127 0,0,238[23] 0,0,255 0,111,184
Magenta 35 45 170,0,170 128,0,128 1,36,86 136,23,152 211,56,211 187,0,187 156,0,156 205,0,205 255,0,255 118,38,113
Cyan 36 46 0,170,170 0,128,128 58,150,221 51,187,200 0,187,187 0,147,147 0,205,205 0,255,255 44,181,233
White 37 47 170,170,170 192,192,192 204,204,204 203,204,205 187,187,187 210,210,210 229,229,229 255,255,255 204,204,204
Bright Black 90 100 85,85,85 128,128,128 118,118,118 129,131,131 85,85,85 127,127,127 127,127,127 128,128,128
Bright Red 91 101 255,85,85 255,0,0 231,72,86 252,57,31 255,85,85 255,0,0 255,0,0 255,0,0
Bright Green 92 102 85,255,85 0,255,0 22,198,12 49,231,34 85,255,85 0,252,0 0,255,0 144,238,144 0,255,0
Bright Yellow 93 103 255,255,85 255,255,0 249,241,165 234,236,35 255,255,85 255,255,0 255,255,0 255,255,224 255,255,0
Bright Blue 94 104 85,85,255 0,0,255 59,120,255 88,51,255 85,85,255 0,0,252 92,92,255[24] 173,216,230 0,0,255
Bright Magenta 95 105 255,85,255 255,0,255 180,0,158 249,53,248 255,85,255 255,0,255 255,0,255 255,0,255
Bright Cyan 96 106 85,255,255 0,255,255 97,214,214 20,240,240 85,255,255 0,255,255 0,255,255 224,255,255 0,255,255
Bright White 97 107 255,255,255 255,255,255 242,242,242 233,235,235 255,255,255 255,255,255 255,255,255 255,255,255

8-bit

As 256-color lookup tables became common on graphic cards, escape sequences were added to select from a pre-defined set of 256 colors:[citation needed]

```   ESC[ 38;5;⟨n⟩ m Select foreground color
ESC[ 48;5;⟨n⟩ m Select background color
0-  7:  standard colors (as in ESC [ 30–37 m)
8- 15:  high intensity colors (as in ESC [ 90–97 m)
16-231:  6 × 6 × 6 cube (216 colors): 16 + 36 × r + 6 × g + b (0 ≤ r, g, b ≤ 5)
232-255:  grayscale from black to white in 24 steps
```

The ITU's T.416 Information technology - Open Document Architecture (ODA) and interchange format: Character content architectures[25] uses ':' as separator characters instead:

```   ESC[ 38:5:⟨n⟩ m Select foreground color
ESC[ 48:5:⟨n⟩ m Select background color
```
256-color mode — foreground: ESC[38;5;#m   background: ESC[48;5;#m
Standard colors High-intensity colors
 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
216 colors
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87
88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123
124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231
Grayscale colors
 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255

24-bit

As "true color" graphic cards with 16 to 24 bits of color became common, Xterm,[19] KDE's Konsole,[26] as well as all libvte based terminals[27] (including GNOME Terminal) support 24-bit foreground and background color setting[better source needed][28]

```   ESC[ 38;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB foreground color
ESC[ 48;2;⟨r⟩;⟨g⟩;⟨b⟩ m Select RGB background color
```

The ITU's T.416 Information technology - Open Document Architecture (ODA) and interchange format: Character content architectures[25] which was adopted as ISO/IEC International Standard 8613-6 gives an alternative version that seems to be less supported:

```   ESC[ 38:2:⟨Color-Space-ID⟩:⟨r⟩:⟨g⟩:⟨b⟩:⟨unused⟩:⟨CS tolerance⟩:⟨Color-Space associated with tolerance: 0 for "CIELUV"; 1 for "CIELAB"⟩; m Select RGB foreground color
ESC[ 48:2:⟨Color-Space-ID⟩:⟨r⟩:⟨g⟩:⟨b⟩:⟨unused⟩:⟨CS tolerance⟩:⟨Color-Space associated with tolerance: 0 for "CIELUV"; 1 for "CIELAB"⟩; m Select RGB background color
```

Note that this uses the otherwise reserved ':' character to separate the sub-options which may have been a source of confusion for real-world implementations. It also documents using '3' as the second parameter to specify colors using a Cyan-Magenta-Yellow scheme and '4' for a Cyan-Magenta-Yellow-Black one, the latter using the position marked as "unused" in the above examples for the Black component.

Also note that many implementation that recognize ':' as the separator erroneously forget about the color space identifier parameter and hence shift the position of the remaining ones.[clarification needed]

Examples

`CSI 2 J` — This clears the screen and, on some devices, locates the cursor to the y,x position 1,1 (upper left corner).

`CSI 32 m` — This makes text green. The green may be a dark, dull green, so you may wish to enable Bold with the sequence `CSI 1 m` which would make it bright green, or combined as `CSI 32 ; 1 m`. Some implementations use the Bold state to make the character Bright.

`CSI 0 ; 6 8 ; "DIR" ; 13 p` — This reassigns the key F10 to send to the keyboard buffer the string "DIR" and ENTER, which in the DOS command line would display the contents of the current directory. (MS-DOS ANSI.SYS only) This was sometimes used for ANSI bombs. This is a private-use code (as indicated by the letter p), using a non-standard extension to include a string-valued parameter. Following the letter of the standard would consider the sequence to end at the letter D.

`CSI s` — This saves the cursor position. Using the sequence `CSI u` will restore it to the position. Say the current cursor position is 7(y) and 10(x). The sequence `CSI s` will save those two numbers. Now you can move to a different cursor position, such as 20(y) and 3(x), using the sequence `CSI 20 ; 3 H` or `CSI 20 ; 3 f`. Now if you use the sequence CSI u the cursor position will return to 7(y) and 10(x). Some terminals require the DEC sequences `ESC 7` / `ESC 8` instead which is more widely supported.

Example of use in shell scripting

ANSI escape codes are often used in UNIX and UNIX-like terminals to provide syntax highlighting. For example, on compatible terminals, the following list command color-codes file and directory names by type.

`ls --color`

Users can employ escape codes in their scripts by including them as part of standard output or standard error. For example, the following GNU sed command embellishes the output of the make command by displaying lines containing words starting with "WARN" in reverse video and words starting with "ERR" in bright yellow on a dark red background (letter case is ignored). The representations of the codes are highlighted.[29]

```make 2>&1 | sed -e 's/.*\bWARN.*/\x1b[7m&\x1b[0m/i' -e 's/.*\bERR.*/\x1b[93;41m&\x1b[0m/i'
```

The following Bash function flashes the terminal (by alternately sending reverse and normal video mode codes) until the user presses a key.[30]

```flasher () { while true; do printf \\e[?5h; sleep 0.1; printf \\e[?5l; read -s -n1 -t1 && break; done; }
```

This can be used to alert a programmer when a lengthy command terminates, such as with `make ; flasher` .[31]

```printf \\033c
```

This will reset the console, similar to the command `reset` on modern Linux systems; however it should work even on older Linux systems and on other (non-Linux) UNIX variants.

Invalid and ambiguous sequences in use

• The Linux console uses `OSC P n rr gg bb` to change the palette, which, if hard-coded into an application, may hang other terminals. However, appending `ST` will be ignored by Linux and form a proper, ignorable sequence for other terminals.[citation needed]
• On the Linux console, certain function keys generate sequences of the form `CSI [ char`. The CSI sequence should terminate on the [.
• Old versions of Terminator generate `SS3 1; modifiers char` when F1–F4 are pressed with modifiers. The faulty behavior was copied from GNOME Terminal.[citation needed]
• xterm replies `CSI row ; column R` if asked for cursor position and `CSI 1 ; modifiers R` if the F3 key is pressed with modifiers, which collide in the case of row == 1. This can be avoided by using the ? private modifier, which will be reflected in the response.[clarification needed]
• many terminals prepend `ESC` to any character that is typed with the alt key down. This creates ambiguity for uppercase letters and symbols @[\]^_, which would form C1 codes.[clarification needed]
• Konsole generates `SS3 modifiers char` when F1–F4 are pressed with modifiers.[clarification needed]

Notes

1. ^ The screen display could be replaced by drawing the entire new screen's contents at the bottom, scrolling the previous screen up sufficiently to erase all the old text. The user would see the scrolling, and the hardware cursor would be left at the very bottom. Some early batch files achieved rudimentary "full screen" displays in this way.
2. ^ Typical colors that are used when booting PCs and leaving them in text mode, which used a 16-entry color table. The colors are different in the EGA/VGA graphic modes.
3. ^ As of Windows XP
4. ^ Until PowerShell 6
5. ^ Campbell theme.
Used as of Windows 10 1709
6. ^ Above color name from X11 rgb.txt color database, with "light" prefixed for the bright colors.
7. ^ For virtual terminals, from /etc/vtrgb.
8. ^ On terminals based on CGA compatible hardware, such as ANSI.SYS running on DOS, this normal intensity foreground color is rendered as Orange. CGA RGBI monitors contained hardware to modify the dark yellow color to an orange/brown color by reducing the green component. See this ansi art Archived 25 July 2011 at the Wayback Machine as an example.

References

1. ^ a b c "Standard ECMA-48: Control Functions for Character-Imaging I/O Devices" (PDF) (Second ed.). Ecma International. August 1979.
2. ^ Williams, Paul (2006). "Digital's Video Terminals". VT100.net. Retrieved 17 August 2011.
3. ^ Heathkit Company (1979). "Heathkit Catalog 1979". Heathkit Company. Archived from the original on 13 January 2012. Retrieved 4 November 2011.
4. ^ "Withdrawn FIPS Listed by Number" (PDF). National Institute of Standards and Technology. 15 December 2016.
5. ^ Mefford, Michael (7 February 1989). "ANSI.com: Download It Here". PC Magazine. Retrieved 10 August 2011.
6. ^ Kegel, Dan; Auer, Eric (28 February 1999). "Nansi and NNansi – ANSI Drivers for MS-DOS". Dan Kegel's Web Hostel. Retrieved 10 August 2011.
7. ^ "PTS-DOS 2000 Pro User Manual" (PDF). Buggingen, Germany: Paragon Technology GmbH. 1999. Archived (PDF) from the original on 12 May 2018. Retrieved 12 May 2018.
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