UNIX - The VI Editor Tutorial

There are many ways to edit files in Unix and for me one of the best ways is using screen-oriented text editor vi.
This editor enable you to edit lines in context with other lines in the file.
Now a days you would find an improved version of vi editor which is called VIM. Here VIM stands for Vi
IMproved.
The vi is g enerally considered the de facto standard in Unix editors because:

• It's usually available on all the flavors of Unix system.
• Its implementations are very similar across the board.
• It requires very few resources.
• It is more user friendly than any other editors like ed or ex.

You can use vi editor to edit an existing file or to create a new file from scratch. You can also use this editor to
just read a text file.

Starting the vi Editor:

There are following way you can start using vi editor:

Following is the example to create a new file testfile if it already does not exist in the current working directory:

As a result you would see a screen something like as follows:

You will notice a tilde (~) on each line following the cursor. A tilde represents an unused line. If a line does not

beg in with a tilde and appears to be blank, there is a space, tab, newline, or some other nonviewable character

present.

So now you have opened one file to start with. Before proceeding further let us understanding few minor but

important concepts explained below.

Operation Modes:

While working withvi editor youwould come across following two modes:

      1. Command mode: This mode enables you to perform administrative tasks such as saving files,

executing commands, moving the cursor, cutting (yanking ) and pasting lines or words, and finding and

replacing . In this mode, whatever you type is interpreted as a command.

      2. Insert mode: This mode enables you to insert text into the file. Everything that's typed in this mode is

interpreted as input and finally it is put in the file .

The vi always starts in command mode. To enter text, you must be in insert mode. To come in insert mode you

simply type i. To g et out of insert mode, press the Esc key, which will put you back into command mode.

Hint: If you are not sure which mode you are in, press the Esc key twice, and then you'll be in command mode.

You open a file using vi editor and start type some characters and then come in command mode to understand the

difference.

Getting Out of vi:

The command to quit out of vi is :q. Once in command mode, type colon, and 'q', followed by return. If your file has

been modified in any way, the editor will warn you of this, and not let you quit. To ignore this messag e, the

command to quit out of vi without saving is :q!. This lets you exit vi without saving any of the chang es.

The command to save the contents of the editor is :w. You can combine the above command with the quit

command, or :wq and return.

The easiest way to save your chang es and exit out of vi is the ZZ command. When you are in command mode,

type ZZ and it will do the equivalent of :wq.

You can specify a different file name to save to by specifying the name after the :w. For example, if you wanted to

save the file you were working as another filename called filename2, you would type :w filename2 and return.

Try it once.

Moving within a File:

To move around within a file without affecting your text, you must be in command mode (press Esc twice). Here

are some of the commands you can use to move around one character at a time:

There are following two important points to be noted:

• The vi is case-sensitive, so you need to pay special attention to capitalization when using commands.
• Most commands in vi can be prefaced by the number of times you want the action to occur. For example,

2j moves cursor two lines down the cursor location.

There are many other ways to move within a file in vi. Remember that you must be in command mode (press Esc

twice). Here are some more commands you can use to move around the file:

Control Commands:

There are following useful command which you can use along with Control Key:

Editing Files:

To edit the file, you need to be in the insert mode. There are many ways to enter insert mode from the commandmode:

Deleting Characters:

Here is the list of important commands which can be used to delete characters and lines in an opened file:

As mentioned above, most commands in vi can be prefaced by the number of times you want the action to occur.

For example, 2x deletes two character under the cursor location and 2dd deletes two lines the cursor is on.

I would highly recommend to exercise allthe above commands properly before proceeding further.

Change Commands:

You also have the capability to chang e characters, words, or lines in vi without deleting them. Here are the

relevant commands:

Copy and Past Commands:

You can copy lines or words from one place and then you can past them at another place using following

commands:

Advanced Commands:

There are some advanced commands that simplify day-to-day editing and allow for more efficient use of vi:

Word and Character Searching:

The vi editor has two kinds of searches: string and character. For a string search, the / and ? commands are

used. When you start these commands, the command just typed will be shown on the bottom line, where you type

the particular string to look for.

These two commands differ only in the direction where the search takes place:

• The / command searches forwards (downwards) in the file.
• The ? command searches backwards (upwards) in the file.

The n and N commands repeat the previous search command in the same or opposite direction, respectively.

Some characters have special meaning s while using in search command and preceded by a backslash (\) to be

included as part of the search expression.

The character search searches within one line to find a character entered after the command. The f and F

commands search for a character onthe current line only. f searches forwards and F searches backwards and

the cursor moves to the position of the found character.

The t and T commands search for a character on the current line only, but for t, the cursor moves to the position

before the character, and T searches the line backwards to the position after the character.

Set Commands:

You can chang e the look and feel of your vi screen using the following :set commands. To use these commands

you have to come in command mode then type :set followed by any of the following options:

Running Commands:

The vi has the capability to run commands from within the editor. To run a command, you only need to g o into

command mode and type :! command.

For example, if you want to check whether a file exists before you try to save your file to that filename, you can

type :! ls and you will see the output of ls on the screen.

When you press any key (or the command's escape sequence), you are returned to your vi session.

Replacing Text:

The substitution command (:s/) enables you to quickly replace words or g roups of words within your files. Here

is the simple syntax:

The g stands for g lobally. The result of this command is that all occurrences on the cursor's line are changed.

IMPORTANT:

Here are the key points to your success with vi:

• You must be in command mode to use commands. (Press Esc twice at any time to ensure that you are in command mode.)
• You must be careful to use the proper case (capitalization) for all commands.
• You must be in insert mode to enter text.