vim

Main commands:

# open file
vi /file_folder/filename

# open file and go to line 25
vi /file_folder/filename ++25

# ON modify mode
i

# OFF modify mode
[Esc]

# undo
u

# save changes
:w [Enter]

# exit without saving
:q! [Enter]

# save changes and exit
:wq [Enter]

# delete line
dd

# delete symbol
x

# copy line
[y]
# paste line
[P]

# find 'text'
/text [Enter]

# find and replace
:%s/OLD/NEW/gc

# show line numbers
:set nu
# hide line numbers
:set nonu