A Quick Guide to vi

por | 9 agosto, 2008

by Wei-Meng Lee
02/21/2003Jaguar includes a few text editors for your editing work. Of these applications, many experienced Unix users will prefer vi (Visual Editor). While users of GUI systems are more familiar with «user friendly» word processors and text editors, vi is a powerful and feature-rich text editor that is lean and efficient.

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However, learning vi requires patience and a little practice; hence, the learning curve is steeper than that of a text editor such as BBEdit. But programmers who regularly use vi swear by it. For some, using vi is a symbol of strength, differentiating the men from the boys.

But what if you need to edit a file quickly in Terminal and don’t have the time to learn and practice vi? In this article, I will present a quick guide to getting you started using vi. Do remember though, topics on vi are enough to fill an entire book, and hence this article is just a tip of the iceberg. Hopefully, it will shed some light on this powerful editor and tempt you to learn more.

Starting vi

To use vi, you need to launch Terminal and at the prompt. Type:

vi textfile

When vi is launched, you should see a window such as the following:

Screen shot.
Figure 1. Starting vi.

The first important thing you should know is that vi operates in two modes–Command mode and Insert mode. Use Command mode to issue commands, such as to delete a line or character. To start typing, you need to use Insert mode. When you first run vi, you will be in Command mode.

Navigating the Cursor

While most terminals support the use of the cursor arrow keys to move the on-screen cursor around, you might want to know that you can also use the normal keys to move the cursor. As shown in Figure 2, you can use the h, j, k and l keys to navigate the cursor:

Screen shot.
Figure 2. Navigating the cursor using the h, j, k and l keys.

At first, this key assignment might feel odd. But with some practice, you’ll get more comfortable. And best of all, you can navigate the cursor without lifting your hand!

Interestingly, to move the cursor five spaces to the right, you can type 5l. To move down three lines, you type 3j, and so on.

To jump to the beginning of a line, press 0 (numeric zero). To jump to the end of a line, press $.

Let’s try to type some text into our file.

Inserting Text

To start typing, we need to go into Insert mode. Press i (to insert a character) and type in the following:

vi is an editor in Unix

hat happens if you make a mistake and want to change it? Chances are, you’ll want to position your cursor at the character to be edited, and by doing so, you use your cursor keys and some strange characters appear. If so, do not panic. Simply press the Esc key to return to Command mode. Pressing the Esc key will switch from Insert mode to Command mode.

Appending Text

Now that you have typed in your first sentence, let’s edit this sentence. I want to sentence to read: «vi is a powerful editor in Unix». So, position your cursor at «a» (the underline indicates the position of your cursor):

vi is an editor in Unix

Press a (for append) and type » powerful». You should now have:

vi is a powerfuln editor in Unix

So what is the difference between a and i? If you pressed i at «a» and type » powerful» you will get:

vi is powerfulan editor in Unix

See the difference?

To insert a new line, simple press the enter key or use o to insert a new line between two lines.

Deleting Text

To delete a character, position the cursor over the character and press x.

To delete an entire word, say, «powerful», position the cursor over the start of the word and press dw, such as:

vi is a powerful editor in Unix

To delete an entire line, position the cursor on the line that you want to delete and press dd. To delete multiple lines, press dnd, where n is the number of lines to delete. For example, d2d will delete two lines.

Saving a File

If you start vi by specifying a filename, you can simply save the file by pressing :w and return. Note that pressing «:» when in Command mode will bring you to the bottom of the screen. This is where you can issue further commands.

If you start vi without any parameters, you need to provide a filename:

:w newfile.txt

You can also use this method to save the file into another file. Note that if the filename you specify already exists, vi will not overwrite the existing file. Instead, use :w! to overwrite the existing file.

Screen shot.
Figure 3. Use ! to overwrite a file.

Inserting a File

There may be times where you need to add the content of another file into your current file. In this case, you can use :r, like this:

:r anotherfile.txt

Simply first position the cursor at the line where you want to insert the file and then press :r.

Quitting vi

To exit from vi, use the :q command. If the file has been modified and you have not saved the changes, vi will not allow you to quit. To quit without saving, use :q!.

Opening a File

If you want to edit another file while you are still in vi, you can use :e to open another file for editing:

:e textfile.txt

Copying, Cutting, and Pasting Text

To copy a block of text, you can use the y (for yank) command. To yank the whole line, press yy.

vi is an editor in Unix
Real programmers use vi!
Have you tried it?
yy copies the line «vi is an editor in Unix»

To copy a word, use yw.

vi is an editor in Unix
Real programmers use vi! 
Have you tried it?
yw copies the word «editor»

To copy from the cursor to the end of the line, use y$.

vi is an editor in Unix
Real programmers use vi!
Have you tried it?
y$ copies the line «editor in Unix»

To paste yanked text, use the p (for put) command.

vi is an editor in Unix
Real programmers use vi!
Have you tried it?
Continuing from the previous y$ example, P (capital p) results in:

vi is an editor in Unixeditor in Unix
Real programmers use vi!
Have you tried it?

p (small p) becomes:

vi is an eeditor in Unixditor in Unix
Real programmers use vi! 
Have you tried it?

Note that for cut operations, you can use the d command (see «Deleting Text») to cut a block of text and p to paste the block of text.

Undoing and Redoing

You can undo your action by pressing u. Note that you can only undo the last action. To redo the same action, use the period (.).

Changing and Replacing Text

You can change the text in your file by using the c command. For example, cw allows you to change the entire word:

vi is an editor in Unix 
Real programmers use vi! 
Have you tried it?
cw Solid (and then press escape) will replace the word «Real» with the word «Solid»

To change the last three words, use c3b.

To change the words starting from the current cursor position to the end of the line, use c$.

To change the words starting from the beginning of the line to the current cursor position, use c0 (numeric zero).

To replace a single character, position the cursor at the character you want to replace and type r, followed by a character.

Searching for Text

To search for a particular piece of text in vi, use the / command followed by the text for which to search. For example, /in will look for the first occurrence of the word «in». To repeat the search, press / and then Enter.

To replace all occurrence of a word in a document, you can use the s command. For example, :s/in/on will replace the first occurrence of the word «in» with the word «on».

:s/in/on/g will replace all occurrences of the word «in» with the word «on» on the current line.

:1,45s/in/on/g will replace all occurrences of the word «in» with the word «on» from line 1 to line 45.

:%s/in/on/g will replace all occurrences of the word «in» with the word «on» in the entire file.

Jumping to a Line

If you are editing a large file, you can jump directly to a line by typing the line number. For example, :4 will position the cursor directly on line four. This is useful when you are debugging a program and the compiler has indicated an error on a particular line.

I hope you find this quick tutorial to vi a useful one. Remember, the more you use vi the more you will enjoy it. Have fun!

Wei-Meng Lee (weimenglee.blogspot.com) is a technologist and founder of Developer Learning Solutions, a technology company specializing in hands-on training of the latest Microsoft technologies.

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