Features of VI Editor - System Software Lab - Lab 4

Introduction

vi is a powerful editor with many features. It can handle very large files much easier than a program like Microsoft Word. Unlike Word, vi is only a TEXT EDITOR and you cannot include graphics or fancy fonts in your file.

Although there are lots of different commands in vi, it is possible to get started using vi knowing only a small subset of them. As you feel more comfortable with vi, you can learn the more advanced features.

vi has 3 modes:

1. write mode, used for entering text
2. command mode and
3. command line mode, used for entering commands to vi.

Remember, in vi, the mouse cannot be used to issue editor commands or move the cursor.

Write Mode

When you first enter the editor, you are in the command mode. To enter the write mode, type the letter a for append. This is one of the four possible commands for entering the write mode. vi is Case Sensitive. Lower case commands are different from upper case commands.

Command Mode

You are in command mode whenever you hit esc to leave the write mode. In command mode, you can move the cursor anywhere in the file.

The x key deletes individual characters, while dd deletes an entire line. To enter the insert mode type the i key. When you're done inserting, hit the "esc" key to return to the command mode.

Command-Line Mode

Command-line mode is used for such things as writing changes and exiting the editor. To enter command-line mode, type : while in command mode. The : will now appear at the bottom of the screen and the command which you type will appear on that line.

1. How to create a new file or modify an existing file:

EXAMPLE:

% vi practice

In this example, the new file "practice" is created if it doesn't already exist.

The screen will look like this after opening a new file entitled, "practice".

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"practice" [New File]

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The Edit Mode

Once in vi, you are placed in the command mode. You cannot enter text in this mode. If you try, the letters you try to type will not appear on the screen. This is because ordinary letters are interpreted as commands.

You must enter the edit mode to type text.

To do so, use one of the following commands. The vi text editor is case sensitive, which means the same letters in upper and lower case have different command responses.

2. How to add information to a file:

What to Type	Result
a	append after the cursor
i	insert before the cursor

The "esc" key must be used to end any of the above commands or to begin any of the following commands (depending on which way you look at it). You must also hit the "esc" key prior to any cursor movement. When in doubt, hit the "esc" key and proceed.

3. How to delete information from a file:

What to Type	Result
x	deletes the character the cursor is under
dd	deletes the line the cursor is on

4. More edit commands

In the command mode, it is possible to move the cursor up, down, left or, right by using the arrow keys on the keyboard. However, no matter what type of keyboard you have, it is possible to use the vi commands, h, j, k, and l, all in lowercase, to control the cursor.

These commands move the cursor as follows:

What to Type	Result
j	moves the cursor up one line
k	moves the cursor down one line
h	moves the cursor backwards on a line
l	moves the cursor forward on a line

5. How to save your work and exit from vi

First you need to enter the command mode by pressing the Escape key.
Now you are ready to give any one of a number of line commands.

What to Type	Result
:wq	saves the current changes and exits vi
:w!	saves the current changes but does not exit vi
:q!	exits vi without saving any change

6. More command lines

Other popular command include

What to type	What it does
ndd (for example 3 dd)	Deletes n number of lines
^	Go to start of line
nY	Copy n number of lines
$	go to end of line
:1	goes to top of file
:5	goes to fifth line of file
:$	goes to bottom of file
:set nu	will number all your lines
:set nonu	turn off line numbering
:1,$s/oldtext/newtext/g	Global substitutions

Vi Quick Reference

ENTERING vi

        vi name        start vi editor with file   name   .

                       The file is created if it doesn't exist.

LEAVING vi

        ZZ             exit from vi, saving changes.

        :q!            exit from vi, discarding changes.

CURSOR POSITIONING

        h              moves left one character position.

        j              moves down one line.

        k              moves up one line.

        l              moves right one character position.

        0       (zero)  moves to the beginning of a line.

        w              moves right one word.

        b              moves left one word.

        CTRL-u         moves up 1/2 screen full.

        CTRL-d         moves down 1/2 screen full.

        G              moves to the bottom of the file.

        nG             moves to line number   n   .

        CTRL-l         clear screen and re-draw.

TEXT MODIFICATION

        itextESC     inserts   text   to the left of the cursor.

                    Insert doesn't cause the cursor to move;

                    text appears as it is typed, terminate with

                    ESC.

        atextESC     appends (inserts) text to the right of

                    the cursor, terminate with ESC.

        RtextESC     Replaces (overprints) characters at the 

                    cursor position, terminate with ESC.

        dd           deletes the line the cursor is on.

        ndd          deletes  n  lines from the cursor position.

        D            deletes characters from the cursor position

                     to the end of the line.

        x            deletes the character at the cursor.

        nx           deletes n characters to the right of the

                     cursor.

        u            undo the last change.

PATTERN SEARCHING

        /pat/        positions the cursor at the next 

                    occurrence of the string pattern.

NOTES:

        ESC     represents the ESC key.  Press the ESC key when 

                it is called for in the above commands.

        CTRL-   represents the CTRL key.  Hold the CTRL key and 

               press the following key simultaneously.

CURSOR POSITIONING

        }       move down one paragraph.

        {       move up one paragraph.

        mx      save the current cursor position and label it

               with the letter x. (x is any letter)

        'x      return to the cursor position labeled x.

TEXT MODIFICATION

        dw      delete the next word.

        .      (period) repeat last change.

        A       append at the end of the current line.

        P       put back deleted line(s).  Text deleted with D

               and dd commands may be pasted back with the P

               command.  Text is pasted in before the cursor

               position.

        :a,bs/old/new/ 

               From line number 'a' to line number 'b', 

               substitute the pattern 'old' with the pattern

               'new'.  You may use any text string which 

               doesn't contain a carriage return in place of 

               the 'old' and 'new' strings.  Use CTRL-G to tell

               what line the cursor is on.

PATTERN SEARCHING

        //      search for the next occurrence of a previously

               specified search string.  

MISCELLANEOUS

        :w      write out current changes.  The vi editor works

               on a copy of your file.  The :w command causes

               the editor to write its copy over the original

               which is on the disk.

        :w name write out changes to the file  name  .  This is

               like the :w command but the changes are written

               into the file you specify.  (good for making

               intermediate copies)

Cut and Paste  Move to the begining of the text to cut.  Use

               dd to delete (cut) several lines.  Use D to cut

               only the end of one line.  Move to the place

               where you wish to paste the text.  Use P to 

               put back the text. You may need to clean up

               the spacing after pasting.