How do I split the Vim window to view two files at once?
:split
The :split command (or s) splits the current window horizontally, creating a new window above with the same file.
All Vim Tricks
How do I show or hide line numbers in Vim?
:set number!
The :set number! command toggles line numbers on or off.
How do I delete all lines matching a pattern?
:g/pattern/d
The :g/pattern/d command deletes every line in the file that matches the given pattern.