ANSI escape sequences

ANSIEscape sequencesAre characters embedded in the text used to control formatting, color, and other output options on video text terminals. almost all terminal emulators designed to show text output from a remote computer, and (portable t for Windows) to show text output from local software, interpret at least some of the ANSI escape sequences.

By default what ever you send to console it is printed as its. For e.g. Consider following echo statement,
$ Echo "Hello World"
Hello World
AboveEchoStatement
Prints sequence of character on screen, but if there is any special
Escape Sequence (control character) in sequence, then first some action
Is taken according to escape sequence (or control character) and then
Normal character is printed on console. For e.g. Following echo command
Prints message in blue color on Console
$ Echo-e "\ 033 [34 m Hello colorful world! "
Hello colorful world!

Above echo statement uses ANSI escape sequence (\ 033 [34 m), Abve entire string (I. e."\ 033 [34 m Hello colorful world! ") Is process as follows

1) first\ 033, Is escape character, which causes to take some action
2) Here it set screen foreground color to blue using[34 mEscape code.
3) then it prints our normal messageHello colorful world!In blue color.

 

Escape sequences start with the characterESC(ASCII decimal 27/Hex 0x1b/Octal 033). You can useEchoStatement to print message, to use ANSI escape sequence you must use-EOption (switch) with ECHO statement, general syntax is as follows Syntax:
Echo-e "\ 033 [Escape-codeYour-message"

 

In above syntax you have to use\ 033 [As its with differentEscape-codeFor
Different operations. As soon as console when es the message it start
To process/read it, and if it found escape character (\ 033) It moves to escape mode, then it read"["Character and movesCommand Sequence Introduction
(CSI) mode. In CSI mode Console reads a series of ascii-coded decimal
Numbers (know as parameter) which are separated by semicolon (;). This numbers are read until console action letter or character is not found (which determines what action to take ).

 

Character or letter	Use in CSI	Examples
H	Set the ANSI Mode	Echo-e "\ 033 [H"
L	Clears the ANSI Mode	Echo-e "\ 033 [l"
M	Useful to show characters in differentColorsOr effects suchBoldAnd blink, see below for parameter taken by M.	Echo-e "\ 033 [35 m Hello World"
Q	Turns keyboard Num Lock, Caps Lock, scroll lock led on or off, see below.	Echo-e "\ 033 [2q"
S	Stores the current cursor X, Y position (COL, row position) and attributes	Echo-e "\ 033 [7 S"
U	Restores cursor position and attributes	Echo-e "\ 033 [8u"

 

And M understood following parameters:

 

0	Reset all attributes to their defaults
1	Set bold
2	Set half-bright (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 normal intensity (ECMA-48 says "doubly underlined ")
22	Set normal intensity
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	Set underscore on, set default foreground color
39	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
49	Set Default background color

 

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