"echo" Command

Learn all about echo command

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echo - display a line of text

It is one of the way to display message and convey information to user which can be used in bash scripts.

root:~# man echo

Example-1

1.1 Default Output

By Default, echo adds new line to the message and prints it on the terminal.

root:~# echo "Hello World !"
Hello World !
root:~#
root:~# echo 'Hello World !'
Hello World !
root:~#

1.2 Removing New Line (-n)

As mentioned, echo appends newline to the message but it can be avoided by using -n option.

root:~# echo -n "Hello World !"
Hello World !root:~#
root:~#
root:~#
root:~# echo -n 'Hello World !'
Hello World !root:~#

Example-2

2.1 Difference between Single(') and Double Quote(")

when single quote is given, echo command takes message as literal string but when double quote is given, variable or command substitution can happen.

root:~# echo "Current Directory [$PWD]"
Current Directory [/root]
root:~# echo 'Current Directory [$PWD]'
Current Directory [$PWD]
root:~#
root:~# echo "Current Directory [`echo Hello $PWD`]"
Current Directory [Hello /root]
root:~# echo 'Current Directory [`echo Hello $PWD`]'
Current Directory [`echo Hello $PWD`]
root:~# NAME=parth
root:~# echo "Hello $NAME"
Hello parth
root:~# echo 'Hello $NAME'
Hello $NAME
root:~#

2.2 Escape Characters (-e) By Default, echo will not understand escape characters but if -e option is given then following sequences are recognized as shown in table.

Sequence	Name
\\	backslash
\a	alert (BEL)
\b	backspace
\c	produce no further output
\e	escape
\f	form feed
\n	new line
\r	carriage return
\t	horizontal tab
\v	vertical tab
\0NNN	byte with octal value NNN (1 to 3 digits)
\xHH	byte with hexadecimal value HH (1 to 2 digits)

root:~# echo "Hello\n\tWorld"
Hello\n\tWorld
root:~# echo -e "Hello\n\tWorld"
Hello
    World


root:~# echo 'This line is not completely \cprinted.'
This line is not completely \cprinted.
root:~# echo -e 'This line is not completely \cprinted.'
This line is not completely root:~#

root:~# echo -e "\vCandidInformation \vis \vall \vabout \vLinux"

CandidInformation
                  is
                     all
                         about
                               Linux
root:~#

Example-3

Characters	Description
*	Anything
[a-z]	Any single character between a to z
[A-Z]	Any single character between A to Z
[0-9]	Any single digit between 0 to 9
?	Any single character

3.1 Special Characater (*)

echo command supports special characters; by doing that echo can work as a ls command. It can be handy in recovery mode.

root:~# echo "/tmp/*"
/tmp/*
root:~# echo /tmp/*
/tmp/1 /tmp/1231131 /tmp/AAA /tmp/BcD /tmp/b /tmp/c /tmp/ffprobe_output /tmp/file1.txt /tmp/file2.txt /tmp/file3.txt /tmp/file4.txt /tmp/hsperfdata_root /tmp/multi-lang-movie.mp4

3.2 Special Characater (*) with some string

root:~# echo /tmp/*.txt
/tmp/file1.txt /tmp/file2.txt /tmp/file3.txt /tmp/file4.txt
root:~# echo /tmp/*.txt1
/tmp/*.txt1

As shown, no files are present with txt1 extension so echo will print string as it is.

3.3 List Files whose name is just single character

root@:~# echo /tmp/?
/tmp/1 /tmp/b /tmp/c

3.4 List Files whose name starts with digit

root@:~# ls /tmp/[0-9]*
/tmp/1    /tmp/1231131

3.5 List Files whose name starts with letters

root@:~# echo /tmp/[a-z]*
/tmp/b /tmp/c /tmp/ffprobe_output /tmp/file1.txt /tmp/file2.txt /tmp/file3.txt /tmp/file4.txt /tmp/hsperfdata_root /tmp/multi-lang-movie.mp4
root@:~# echo /tmp/[A-Z]*
/tmp/AAA /tmp/BcD
root@:~# echo /tmp/[a-zA-Z]*
/tmp/AAA /tmp/BcD /tmp/b /tmp/c /tmp/ffprobe_output /tmp/file1.txt /tmp/file2.txt /tmp/file3.txt /tmp/file4.txt /tmp/hsperfdata_root /tmp/multi-lang-movie.mp4

Example-4

4.1 Colored Output

Color	ForeGround Normal Code	ForeGround Bright Code	Background Code
Black	0;30	N.A.	40
Red	0;31	1;31	41
Green	0;32	1;32	42
Yellow	0;33	1;33	43
Blue	0;34	1;34	44
magenta	0;35	1;35	45
Cyan	0;36	1;36	46
Gray	1;30	0;37	47
White	1;37	N.A.	0

N.A. - Not Applicable

Use the following template for writing colored text on a colored background.

echo -e '\ESC[COLOR1;COLOR2mYOUR TEXT GOES HERE.\ESC[00m'

The \ESC[ begins the escape sequence. Based on ASCII table value should be \033. The semicolon-separated numbers COLOR1 and COLOR2 specify a foreground and a background color, according to the table above. The order of the numbers does not matter, since the foreground and background numbers fall in non-overlapping ranges.Next, the m terminates the escape sequence, and the text begins immediately after that.

Info! Dont forget to end your Text with \033[00m; otherwise output will change your terminal background color too. \033[00m means, we are terminating with no color !

root@:~# echo -e "\033[0;31;44mThis prints text in red color with blue background\033[00m"
This prints text in red color with blue background

root@:~# echo -e "\033[1;33;42mThis prints text in yellow color with green background\033[00m"
This prints text in yellow color with green background