vi (already exist file name) : Go to the edit file. To begin edit we should command i or I or o or O

i edit begin from end

I edit begin from start

o edit begin from new line

O edit begin after leave one line space

When we finish editing we can click esc. After that we are in command mode. Then we should command :wq or :qa! or :w

:wq exit while saving

:qa! Exit without saving

:w save

When we are in command mode we can select text , copy that text and paste. Shift + v select (we can go with arrow keys). Click y for copy and p for paste

vi (new file name) : Creating new file and start edit that file

cat > file name : Create a new file

cat (file name) : Displays the file

head (file name) : Displays begin part of file

tail (file name) : Displays end part of file

head -5 (file name) : Displays first 5 line of file

less (file name) : It displays file only screen limit

echo $PATH : Displays the contents of variables

clear : Clear the screen

exit : Exit the shell

df -h : Shows all the disk spaces in system

uptime : Uptime of my system

hostname : My host name

uname : What is the operating system

man (command) : Details about particular command