CS 3723
Programming Languages 
  vi Editor   

The vi editor: This is an old-fashioned text-file editor in the Unix world. It uses the full screen (or full window), but it does not use a mouse. It is useful because it should always be available and should always work. vi is enormously complicated -- whole books cover just this editor. It is notoriously confusing for beginners, but you can get by very well with just the 18 commands given in the next section.

For common editing tasks, a mouse-based editor is often more appropriate. Very intricate editing might better be done with a shell script or with a scripting language such as Python or Ruby or even (ugh!) Perl.

The vi editor has been superseded by vim, which is mostly downward compatible with vi. There's a lot on-line about these editors.

Unix commands below are in bold green.

The basics:

Basics of vi: 18 commands, most of what you need
To enter the vi editor, type vi on the command line followed by a file name to create or open:

    % vi file.c

Produces a clear screen if it's a new file, with ~ running down the left side.

You can get by with a very short list of commands (18 of them):

    i, I: -insert or insert at start of line, and enter input mode
    a, A: -append or append at end of line, and enter input mode
    Esc: -leave input mode, enter command mode
    x, dd: -delete a char, delete a line (in command mode only)
    h, l, j, k: -move left, right, up, down (in command mode only)
    ZZ: -save changes, exit vi (in command mode only)
    :w, :w filename: -write, write to "filename", no exit (in command mode)
    :q, :q!: -quit and don't save, quit and don't save even if changes (in command mode)
    /sometext: -search for "sometext" (in command mode)
    :23: -go to line 23 (in command mode)

If in doubt, press "Esc". Then type ":q!" (to exit vi without saving changes), and start over.

Remember, in input mode (after an i, I, a, or A command), all key strokes except Esc become a character in the file.

Carrying on: Below are useful commands to make editing more convenient. Try to relate these to the word processing techniques you use in the gui world with a mouse.

"Command mode"

  • cursor movements:

    • To replace the arrow keys
        h  -left one character
        l   -right one character
        j   -down one line
        k  -up one line

    • In windows you can use ctrl and the arrows to move words by words, here it's
        w  -right one word
        b   -back one word

    • Home key and End key are
        $   -to the end of line
        0   -to the beginning of the line

    • Other useful keys
        )   -right one sentence
        (   -left one sentence
        }   -right one paragraph
        {   -left one paragraph

    • Page down and page up
        <Ctrl-F>   -forward one page
        <Ctrl-B>   -back one page

  • deleting (or cutting to the clipboard):
      d  - delete (then add one of the cursor movement symbols toshow what should be deleted)
      d$ -delete to end of line
      d0  -delete to the beginning of the line
      dw  -delete the current or next word
      dd  -delete delete (delete the whole line)
      x  -delete character cursor is on

  • other basic commands:
        r  -replace one character
        ZZ  -save and exit (hold down shift and press "z" twice)
        u -undo last editing command (only once)
        /sometext  -search for "sometext", a very useful command

    • Copy
        y -yank (otherwise known as copy)
        yy - copy the current line
        yw  -copy the current word and the 4 to the right
        y0  -copy to the beginning of the line
        Y  -yank line cursor is on

    • Paste
        p -paste below the current line if buffer contains a newline character, otherwise, paste to left of current character
        P -paste above the current line if buffer contains a newline character, otherwise, paste to right of current character

  • any command can take numeric argument before the name of "object", i.e.
      5dd  -delete 5 lines beginning with cursor line (or)
      d5d  - same as above
      2dw  -delete two words to right
      d2b  - delete two words to left
      c3w>  -change 3 words
      3<Ctrl-B>  -move up three pages

  • command line (sometimes called "ex mode"):
      :

  • in ex mode "set" command can be executed to customize editing environment, i.e.:
      :set all   -will show the state of all options
      :set number  -will show on the screen numbers of all lines
      :set autoindent  -holds previous line's indention

  • in ex mode any ex command can be performed on the range of lines, i.e.:
      :18,24 del -delete from line 18 to line 24
      :23,48 copy 17 -block from line 23 to 48 copy to line 17
      :2,17 move 92 -block from line 2 to 17 move to line 92

  • file commands in ex mode:
      :r somefile  -read in "somefile"
      :x  -save and exit (if file is "Read Only", this command will exit without saving)
      :wq  -write and quit (same as above)
      :w  -write (save)
      :w somefile  -save this file as "somefile"
      :q  -quit without saving
      :q!  -quit without saving if changes were made
      :23  -go to line 23, very useful when debugging

"Input Mode" - editing your code...

  • text input commands (all require "Esc" to terminate):
      i  -insert text before the character cursor is on
      I  -insert text at the beginning of the line
      a  -append (insert text after the character cursor is on)
      A  -append text to the end of the line
      c  -change (replace previous text with new one) example:
      c3w  -change 3 words to the right of cursor
      R  -start overwriting text
      o  -start entering text at the beginning of the new line below the cursor
      O  -start entering text at the beginning of the new line above the cursor

  • if in doubt, press "Esc"

Regular Expressions and Substitution: Regular expressions are not mentioned above, but they can be used within vi with great effectiveness. especially in combination with the s (substitution) command, which is also not mentioned above. However, it probably makes more sense now to use a scripting language that supports regular expressions.

( Revision date: 2014-05-21. Please use ISO 8601, the International Standard.)