VI editor

VI is useful in a CLI-only envireonment, especially when changing remote configurations in a service.

Basics

• vi sample.txt Creates a text file
• A tilde ~ represents an unused line; if there is an empty line without the tilde, there is a newline or tab character present
• :q! quits the editor (quit)
• :w! saves the change in file (write)
• :w newfile.txt save as newfile.txt
• :wq! saves the file and quits the editor

Modes in VI

VI is a model editor that has two modes: Command and Insert

1. Command mode
   • Default mode
   • Enables administrative tasks (i.e. saving the file, executing commands, moving cursor, etc)
   • Use this mode when you want to move around the file without changing it (“a safe place”)
2. Insert mode
   • Enables you to insert text into file
   • Hit i to change to insert mode
   • Hit esc to get out of insert mode`

Making changes in file

• Deleting
  • dd: delete a whole line
    • n dd: delete n lines
  • D: delete the text on the right side of the cursor
• Reverting
  • u: undo the last action
  • Ctrl r: redo the last action

Command mode

• Searching
  • Special characters must be preceded by a backslash (i.e. \n)
  • Hit Enter: take cursor to the first character of the first match
  • /pattern performs a forward search; it pattern matches the text after the cursor
    • N to continue searching
  • ?pattern performs a backward search; it pattern matches the text before the cursor
    • n to continue searching
• Search and replace
  • :%s/pattern/replace/gc
    • Replace pattern with replace
    • g changes all occurences (greedy)
    • c asks for confirmation
• Changing display using :set
  • nu: display line numbers on the left hand side
  • wm: word wrap the text
    • wm=2: set word wrap margin to 2 characters