Editing a File on Unix with vi - Basic Commands.

What is  vi?

The default editor that comes with the UNIX operating system is called  vi ( visual editor). [Alternate editors for UNIX environments include  pico and  emacs, a product of GNU.]

The UNIX  vi editor is a full screen editor and has two modes of operation:

  1. Command mode commands which cause action to be taken on the file, and
  2. Insert mode in which entered text is inserted into the file.

In the command mode, every character typed is a command that does something to the text file being edited; a character typed in the command mode may even cause the  vi editor to enter the insert mode. In the insert mode, every character typed is added to the text in the file; pressing the  <Esc> ( Escape) key turns off the Insert mode.

While there are a number of  vi commands, just a handful of these is usually sufficient for beginning  vi users. To assist such users, this Web page contains a sampling of basic  vi commands. The most basic and useful commands are marked with an asterisk ( * or star) in the tables below. With practice, these commands should become automatic.

NOTE: Both UNIX and  vi are  case-sensitive. Be sure not to use a capital letter in place of a lowercase letter; the results will not be what you expect.

To Get Into and Out Of  vi

To Start  vi

To use  vi on a file, type in  vi filename. If the file named  filename exists, then the first page (or screen) of the file will be displayed; if the file does not exist, then an empty file and screen are created into which you may enter text.

* vi filename edit  filename starting at line 1
  vi -r filename recover  filename that was being edited when system crashed

To Exit  vi

Usually the new or modified file is saved when you leave  vi. However, it is also possible to quit  vi without saving the file.

Note: The cursor moves to bottom of screen whenever a colon ( :) is typed. This type of command is completed by hitting the  <Return> (or  <Enter>) key.

Basic Command Command Description
here :x <Return> quit  vi, writing out modified file to file named in original invocation
  :wq <Return> quit  vi, writing out modified file to file named in original invocation
  :q <Return> quit (or exit)  vi
 *  :q! <Return> quit  vi even though latest changes have not been saved for this  vi call

Moving the Cursor

Unlike many of the PC and MacIntosh editors,  the mouse does not move the cursor within the  vi editor screen (or window). You must use the the key commands listed below. On some UNIX platforms, the arrow keys may be used as well; however, since  vi was designed with the Qwerty keyboard (containing no arrow keys) in mind, the arrow keys sometimes produce strange effects in  vi and should be avoided.

If you go back and forth between a PC environment and a UNIX environment, you may find that this dissimilarity in methods for cursor movement is the most frustrating difference between the two.

In the table below, the symbol  ^ before a letter means that the  <Ctrl> key should be held down while the letter key is pressed.

Basic Command Command Description
* j  or  <Return>   [ or down-arrow] move cursor down one line
* k [ or up-arrow] move cursor up one line
* h  or  <Backspace>   [ or left-arrow] move cursor left one character
* l  or  <Space>   [ or right-arrow] move cursor right one character
* 0 (zero) move cursor to start of current line (the one with the cursor)
* $ move cursor to end of current line
  w move cursor to beginning of next word
  b move cursor back to beginning of preceding word
  :0 <Return>  or 1G move cursor to first line in file
  :n <Return>  or nG move cursor to line  n
  :$ <Return>  or G move cursor to last line in file

Screen Manipulation

The following commands allow the  vi editor screen (or window) to move up or down several lines and to be refreshed.

Basic Command Command Description
  ^f move forward one screen
  ^b move backward one screen
  ^d move down (forward) one half screen
  ^u move up (back) one half screen
  ^l redraws the screen
  ^r redraws the screen, removing deleted lines

Adding, Changing, and Deleting Text

Unlike PC editors, you cannot replace or delete text by highlighting it with the mouse. Instead use the commands in the following tables.

Perhaps the most important command is the one that allows you to back up and  undo your last action. Unfortunately, this command acts like a toggle, undoing and redoing your most recent action. You cannot go back more than one step.

* u UNDO WHATEVER YOU JUST DID; a simple toggle

The main purpose of an editor is to create, add, or modify text for a file.

Inserting or Adding Text

The following commands allow you to insert and add text. Each of these commands puts the  vi editor into insert mode; thus, the  <Esc> key must be pressed to terminate the entry of text and to put the  vi editor back into command mode.

Basic Command Command Description
* i insert text before cursor, until  <Esc> hit
  I insert text at beginning of current line, until  <Esc> hit
* a append text after cursor, until  <Esc> hit
  A append text to end of current line, until  <Esc> hit
* o open and put text in a new line below current line, until  <Esc> hit
* O open and put text in a new line above current line, until  <Esc> hit

Changing Text

The following commands allow you to modify text.

Basic Command Command Description
* r replace single character under cursor (no  <Esc> needed)
  R replace characters, starting with current cursor position, until  <Esc> hit
  cw change the current word with new text, starting with the character under cursor, until  <Esc> hit
  cNw change  N words beginning with character under cursor, until  <Esc> hit;   e.g.,  c5w changes 5 words
  C change (replace) the characters in the current line, until  <Esc> hit
  cc change (replace) the entire current line, stopping when  <Esc> is hit
  Ncc  or  cNc change (replace) the next N lines, starting with the current line, stopping when  <Esc> is hit

Deleting Text

The following commands allow you to delete text.

Basic Command Command Description
* x delete single character under cursor
  Nx delete N characters, starting with character under cursor
  dw delete the single word beginning with character under cursor
  dNw delete  N words beginning with character under cursor;   e.g.,  d5w deletes 5 words
  D delete the remainder of the line, starting with current cursor position
* dd delete entire current line
  Ndd  or  dNd delete  N lines, beginning with the current line;   e.g.,  5dd deletes 5 lines

Cutting and Pasting Text

The following commands allow you to copy and paste text.

Basic Command Command Description
  yy copy (yank, cut) the current line into the buffer
  Nyy  or  yNy copy (yank, cut) the next N lines, including the current line, into the buffer
  p put (paste) the line(s) in the buffer into the text after the current line

Other Commands

Searching Text

A common occurrence in text editing is to replace one word or phase by another. To locate instances of particular sets of characters (or strings), use the following commands.

Basic Command Command Description
  /string search forward for occurrence of  string in text
  ?string search backward for occurrence of  string in text
  n move to next occurrence of search string
  N move to next occurrence of search string in opposite direction

Determining Line Numbers

Being able to determine the line number of the current line or the total number of lines in the file being edited is sometimes useful.

Basic Command Command Description
  :.= returns line number of current line at bottom of screen
  := returns the total number of lines at bottom of screen
  ^g provides the current line number, along with the total number of lines, In the file at the bottom of the screen

Saving and Reading Files

These commands permit you to input and output files other than the named file with which you are currently working.

Basic Command Command Description
  :r filename <Return> read file named  filename and insert after current line (the line with cursor)
  :w <Return> write current contents to file named in original  vi call
  :w newfile <Return> write current contents to a new file named  newfile
  :12,35w smallfile <Return> write the contents of the lines numbered 12 through 35 to a new file named  smallfile
  :w! prevfile <Return> write current contents over a pre-existing file named  prevfile
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