Vim handy commands

Vim

1. Copy/duplicate current line (on the next line)
- In normal mode,
  :t.
2. Duplicate line on line 7
- In normal mode,
  :t 7

3. Save changed file as sudo which was opened as a user with less access
  :w !sudo tee %

  Explanation
  :w – write
  !sudo – call shell sudo command
  tee – the output of write (:w) command is redirected using tee
  % – current file name
  
4. undo
 - Normal mode
  press 'u'
  
5. redo
  - Normal mode
  ctrl + 'r'
  
6. Search and replace
  - Normal mode
  
  :%s/foo/bar/gc
  
  Change each(g) 'foo' to 'bar', but ask for confirmation(c) first.