Vi Editor

The UNIX visual editor, vi, is a command-driven screen editor. It is case-sensitive. Uppercase and lowercase letters are treated differently. WQ is interpreted differently than wq. Using the vi editor, you can create and modify text files. The initial vi screen is illustrated below:

The tildes (~) indicate nonexistent lines, which are not the same as lines that contain blanks. When you enter vi your cursor will be positioned at the upper left-hand corner of the screen and you will be in command mode.

Modes

Vi has two modes: 1) the command mode and 2) the insert or append mode.

When vi is executed you are placed in the command mode. In the command mode, you can move around the file using the directional (cursor movement) arrow keys or the forward search command (/word). To add text to the file, you must leave the command mode and go into the append mode. TO do this, ou can use commands such as A, a, I, i, O, or o. Once you enter on e of these commands, you are in the append mode. These commands operate as follows:

While you are in insert (append) mode, whatever you type is added to the file until you press ESC to return to the command mode.

The ESC key is the essential component of the visual editor. Whenever you are in doubt about where you are in vi - command or append mode - press the ESC key. In the append mode, ESC moves you to the command mode. IN the command mode, ESC produces a beep or flash, indicating you are already in the command mode.

Creating and Editing

To create a file with vi, begin the procdess by typing vi filename. (If youa re using elm to send mail, the elm program invokes vi for you.) The screen clears and the initial vi screen with tildes (~) appears. You are in command mode at this point. GO into the append mode and add your text. If you make a typing mistake while entering the line use the delete key to backup and correct it. (Remember, if you wish to use the directional arrow keys you must press ESC and get into the command mode. A common error is to try to move the cursor while you are in append mode instead of command mode. If you do this, a string of strange characters such as ^K^K^L^L or ^[A^[B will appear on the screen. Should this happen, press ESC and use the x command to delete the unwanted characters.) After you have entered your text into vi, you must instruct vi to save it. TO save the file, you must return to command mode by pressing ESC. In the command mode press the coloe (:) key. A colon (:) will appear in the lower left-hand corner of your screen. This line is called the vi command line and is reserved for entering certain vi commands such as:

To edit an existing file, begin the process by typing vi filename. The file will be displayed on the screen. The process then becomes the same as indicated above with creating - change to apend mode, make your changes, and save the file.

Saving and Exiting (Quiting)

To save a file in vi you must be in the command mode. From the command mode, type a colon (:) followed by one of the following vi commands:

To exit (quit) the editor you must be in command mode. To exit without saving changes type a colon (:) followed by one of the following vi commands:

Vi Command Summary

Mode-changing
ESC escape from text append (insert) mode and return to vi command mode
:q quit work on a file if no changes have been made
:q! quit work on a file but do not write changes
:w write the current file to filename
:wq write changes and quit work on the file

cursor positioning
<- move cursor one space left
-> move cursor one space right
0 (zero) move cursor to first position of current line
$ move cursor to last position of current line
G move cursor to last line in file
NG move cursor to line number n
:n move to line number n
- move cursor to first character of next line
+ move cursor to last line displayed on the screen
H move cursor to top line displayed on screen

Display adjusting
Ctrl f scroll forward one screen
Ctrl b scroll backward one screen
Ctrl l refresh the screen

Edit commands
A append at end of line
a append after cursor
I insert at beginning of line
i insert before cursor
O open a line above current line
o open a line below current line
ESC terminate append (insert) mode
dd delete current line
ndd delete n number of lines
D delete reminder of line
x delete current cursor position
X delete back one character

Searching commands
/word search forward for word
n repeat previous search

Miscellaneous commands
:r file read in contents of file
!! repeat last system command