sudo apt install vim
vim <filename>
# "i" key - enters insert mode
# "ESC" key - switch to command mode
# In command mode
:wq # save and quit
:q! # force quit without save
dd # delete entire line
d5 # delete next 5 lines
u # undo
A # jump to end of line and switch to insert mode
0 # jump to start of the line
$ # jump to end of the line
10G # jump to line 10
/<string> # search for string
n # jump to next match
N # search in opposite direction
:%s/old/new # replace 'old' with 'new' throughout the file