Linux - Useful vi function

Input : a、i、o
First Line : gg
Last Line : G
Goto Line : xxG
Goto neginning of line : 0
Goto end of line : $
Copy line : yy
Paste : p
Undo : u
Delete word : x
Delete line : dd
Show Line No. : :set nu
Hide Line no. : :set nonu
Goto shell : :sh（back to vi : exit）