Echo command

Echo command: Write arguments to the standard output. (write parameters to dimension output)

Echo sends the input string to standard output. The output string is separated by a blank character with a newline number at the end

Echo [- ne] [string]

NAME

Echo-display a line of text

SYNOPSIS

Echo [SHORT-OPTION]... [STRING]...

Echo LONG-OPTION

Options:

-n: cancel the last automatic line wrapping

-e: if the following character appears in the string, it will be specially treated instead of outputting it as a normal character

\ a sound of warning

\ b Delete the previous character

[root@centos7 ~] # echo-e "he\ bllo"

Hllo

\ c No newline character is added at last

[root@centos7 ~] # echo-e "he\ cllo"

He [root@centos7 ~] # echo-e "hello\ c"

Hello [root@centos7 ~] # ^ C

\ f wrap but the cursor remains in its original position

[root@centos7 ~] # echo-e "he\ fllo"

He

Llo

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

[root@centos7 ~] # echo-e "he\ nllo"

He

Llo

\ r move the cursor to the beginning of the line, but do not wrap

[root@centos7 ~] # echo-e "hello\ rman"

Manlo

\ t insert Tab

[root@centos7 ~] # echo-e "hello\ tman"

Hello man

\ v is the same as\ f

[root@centos7 ~] # echo-e "he\ vllo"

He

Llo

\ insert\ character

[root@centos7 ~] # echo-e "he\\ llo"

He\ llo

\ nnn inserts ASCII characters represented by nnn (octal)

[root@centos7 ~] # echo-e "hello\ 052"

Hello*

Echo display color output:

Echo can change the color of the output text, and the desired-e option can be used to generate the display color of the text using the "ANSI unconventional character sequence".

Such as

Use echo to display a triangle with flashing, underlining, color (optional)

[root@centos7 ~] # echo-e "\ 033 [40 × 31 * 4 * 5m *\ n *\ n * *\ n *\ 033 [0m"

\ 033 [40 position 31x 4x 5m means to set the black background to the red foreground, turn on the underline and flash.

\ nindicates a line break and skip to the beginning of the line

\ 033 [0m means to reset the attribute and end the unconventional character sequence

Note:\ 033 guides the unconventional character sequence,\ 033 [indicates the beginning of the terminal escape character;\ 033 is the ASCII code of the exit key ESC, m indicates setting the attribute, and then ends the unconventional character sequence. In this example, 40 represents a black background, 31 represents a red foreground, 4 indicates underlining on, and 5 indicates flicker on. The numerical value has nothing to do with the order in which it is encoded. Specific values can be viewed in the ANSI standard color table.