Shulou(Shulou.com)06/01 Report--

Echo command between single and double quotation marks between strings and variables

"weak reference, command unrecognized, variable recognition.

Strong quotes, silly symbols, and any command is a string in his eyes. The command is not recognized and the variable is not recognized.

~ Command references, the cleverest, execute commands in the display. Command recognition, variable identification.

When one command invokes another command, $() = ~

For example: tough ~ whoami~= creates a root file

The function of the echo command is to display a piece of text on the monitor, which generally acts as a prompt.

The general format of the command is: echo [- n] string

The option n means that the output text is not wrapped; the string can be in quotation marks or not. When using the echo command to output the quoted string, the string will be output as is; when using the echo command to output the string without quotation marks, each word in the string will be output as a string, and each string will be separated by a space.

Function description: display text.

Syntax: echo [- ne] [string] or echo [--help] [--version]

Additional note: echo sends the input string to standard output. The output strings are separated by blank characters and are followed by a newline number.

Parameter: echo-n output without line wrapping

For example: echo-n "123"; echo "456"

Final output

123456

Instead of

one hundred and twenty three

four hundred and fifty six

Echo-e handles special characters (escape characters)

Text output:

\ a sound of warning

\ b delete the previous character; Backspace key

\ C finally, no newline symbol is added, the recycled newline is compressed, no newline is added, and the opposite is true.

\ f Wrap line, but the cursor remains in its original position

\ nWrap and the cursor moves to the beginning of the line

\ r move the cursor to the beginning of the line, but do not wrap it; move the cursor to the front, and then replace the characters with the same number of digits

\ t insert tab

\ v is the same as\ f

\ insert\ character

\ 0nnn inserts ASCII characters represented by nnn (octal)

Echo-e'\ 0101'= A

Echo-e "\ 033 [43 × 31mred" = 43 × × × background .31 red font (41-47 background, 31-37 font)

Echo-e "\ 033 [43 × 31mred color\ 033 [0m" can end the front background and wrap to show the red background color

Each file will define a different color (.gz: .exe, etc.), enter cat / etc/DIR_COLORS, you can see the color of the file name suffix, # .exe means no color, delete # will work, there will be color. And the file suffix color can be modified by nano.

Word background color range: 40 Muhami Muhami 49

40: White characters on black background

41: White characters with crimson background

42: White characters with green background

43: × × white characters at the bottom

44: White words on blue background

45: White characters on purple background

46: White characters with dark green background

47: black words on a white background

Word color: 30Mui Mui Mui 39

30: black

31: red

32: green

33: yellow

34: blue

35: purple

36: dark green

37: White

Description of ANSI control code

\ 33 [0m turn off all properties

\ 33 [1m set high brightness

\ 33 [4m underline

\ 33 [5m flicker

\ 33 [7m reverse display

\ 33 [8m blanking

\ 33 [30m--\ 33 [37m set foreground color

\ 33 [40m--\ 33 [47m set background color

\ 33 [nA cursor up n lines

\ 33 [nB cursor down n lines

\ 33 [move the nC cursor to the right n lines

\ 33 [nD cursor move left n lines

\ 33 [ytrexh sets the cursor position

\ 33 [2J clear screen

\ 33 [K clear the contents from the cursor to the end of the line

\ 33 [s Save cursor location

\ 33 [u restore cursor position

\ 33 [? 25l hide the cursor

\ 33 [? 25h display cursor

\ xHH inserts ASCII characters represented by HH (hexadecimal)

If the code is garbled, reset resets the screen

-help display help

-version displays version information

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