Tuesday, January 8, 2019

Cheat sheet for echo


The syntax for echo is:
echo [option(s)] [string(s)]
1. Input a line of text and display on standard output
$ echo Tecmint is a community of Linux Nerds 
Outputs the following text:
Tecmint is a community of Linux Nerds 
2. Declare a variable and echo its value. For example, Declare a variable of x and assign its value=10.
$ x=10
echo its value:
$ echo The value of variable x = $x 
The value of variable x = 10 
Note: The ‘-e‘ option in Linux acts as interpretation of escaped characters that are backslashed.
3. Using option ‘\b‘ – backspace with backslash interpretor ‘-e‘ which removes all the spaces in between.
$ echo -e "Tecmint \bis \ba \bcommunity \bof \bLinux \bNerds" 
TecmintisacommunityofLinuxNerds 
4. Using option ‘\n‘ – New line with backspace interpretor ‘-e‘ treats new line from where it is used.
$ echo -e "Tecmint \nis \na \ncommunity \nof \nLinux \nNerds" 
Tecmint 
is 
a 
community 
of 
Linux 
Nerds 
5. Using option ‘\t‘ – horizontal tab with backspace interpretor ‘-e‘ to have horizontal tab spaces.
$ echo -e "Tecmint \tis \ta \tcommunity \tof \tLinux \tNerds" 
Tecmint  is  a  community  of  Linux  Nerds 
6. How about using option new Line ‘\n‘ and horizontal tab ‘\t‘ simultaneously.
$ echo -e "\n\tTecmint \n\tis \n\ta \n\tcommunity \n\tof \n\tLinux \n\tNerds" 
Tecmint 
is 
a 
community 
of 
Linux 
Nerds 
7. Using option ‘\v‘ – vertical tab with backspace interpretor ‘-e‘ to have vertical tab spaces.
$ echo -e "\vTecmint \vis \va \vcommunity \vof \vLinux \vNerds" 
Tecmint 
is 
a 
community 
of 
Linux 
Nerds 
8. How about using option new Line ‘\n‘ and vertical tab ‘\v‘ simultaneously.
$ echo -e "\n\vTecmint \n\vis \n\va \n\vcommunity \n\vof \n\vLinux \n\vNerds" 
Tecmint 
is 
a 
community 
of 
Linux 
Nerds 
Note: We can double the vertical tab, horizontal tab and new line spacing using the option two times or as many times as required.
9. Using option ‘\r‘ – carriage return with backspace interpretor ‘-e‘ to have specified carriage return in output.
$ echo -e "Tecmint \ris a community of Linux Nerds" 
is a community of Linux Nerds 
10. Using option ‘\c‘ – suppress trailing new line with backspace interpretor ‘-e‘ to continue without emitting new line.
$ echo -e "Tecmint is a community \cof Linux Nerds" 
Tecmint is a community avi@tecmint:~$ 
11. Omit echoing trailing new line using option ‘-n‘.
$ echo -n "Tecmint is a community of Linux Nerds" 
Tecmint is a community of Linux Nerdsavi@tecmint:~/Documents$ 
12. Using option ‘\a‘ – alert return with backspace interpretor ‘-e‘ to have sound alert.
$ echo -e "Tecmint is a community of \aLinux Nerds" 
Tecmint is a community of Linux Nerds
Note: Make sure to check Volume key, before firing.
13. Print all the files/folder using echo command (ls command alternative).
$ echo * 
103.odt 103.pdf 104.odt 104.pdf 105.odt 105.pdf 106.odt 106.pdf 107.odt 107.pdf 108a.odt 108.odt 108.pdf 109.odt 109.pdf 110b.odt 110.odt 110.pdf 111.odt 111.pdf 112.odt 112.pdf 113.odt linux-headers-3.16.0-customkernel_1_amd64.deb linux-image-3.16.0-customkernel_1_amd64.deb network.jpeg 
14. Print files of a specific kind. For example, let’s assume you want to print all ‘.jpeg‘ files, use the following command.
$ echo *.jpeg 
network.jpeg 
15. The echo can be used with redirect operator to output to a file and not standard output.
$ echo "Test Page" > testpage 
## Check Content
avi@tecmint:~$ cat testpage 
Test Page 
echo Options
 Options Description
 -n do not print the trailing newline.
 -e enable interpretation of backslash escapes.
 \b backspace
 \\ backslash
 \n new line
 \r carriage return
 \t horizontal tab
 \v vertical tab

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