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Basic UNIX Commands for Beginners: vi Tutorial - Part I
Regardless of what you use a UNIX or Linux system
for, you will sooner or later need to create a new text file or edit
the text in an existing file. In order to accomplish this task you
will need to know how to use a text editor. This tutorial will teach
you the basics of using the vi text editor.
The vi editor is available on most systems running the UNIX or Linux
operating system (it's also commonly found on computers running other
operating systems), is widely used by UNIX and Linux users, and is
perfect for editing files over remote or low-speed connections.
[ If you are new to UNIX and need an overview of
important UNIX commands and concepts, check out our Basic UNIX Commands and Concepts Tutorial for
Beginners ]
Since vi has a large number of features to support its extensive
functionality, this vi tutorial is designed to just introduce you to
the basics so that you can start using vi immediately.
(1) Entering vi
When you start the vi editor, you can…
(a) open an existing file for editing:
$ vi existing-filename
(b) open a new file for editing:
$ vi new-filename
(c) start editing a file without specifying the name of a file:
$ vi
If you open an existing file, you will see the contents of the file.
The lines following the file's contents will contain a single ~
(tilde) character at the beginning of each line. These lines will not
become part of the file's contents until text is added to them. When
you start vi with the name of a new file or without specifying a name,
every line except the first (top) line will have a ~ in the first
position of the line.
The vi editor does all of its work in a work buffer. This means that
the editing you do is not written to disk until you exit vi or
explicitly instruct vi to write (save) the buffer's contents to disk.
When you start a vi session, the default mode of operation is Command
Mode. This means that vi is ready to receive and act on the commands
you give it. This may at first be a little strange to you because word
processors by default start in Input Mode, ready to add text
immediately.
In Command Mode you can maneuver the cursor through the work buffer,
delete or copy and paste text, save the work buffer's contents to
disk, and exit the vi session. All keystrokes in this mode are
interpreted as commands, are not displayed to the screen, and do not
require you to press the Enter key for them to be executed.
(2) Exiting (Quiting) vi
There are several different ways you can exit a vi editor session. To
exit (quit) vi from Command Mode, you would use the ZZ (two uppercase
z's) command. As mentioned in the previous section the two Z's will
not be displayed to the screen. The contents of the work buffer will
be written to disk prior to exiting the editing session and then you
will be returned to the command prompt.
You can also exit the editor from what's called Last Line Mode. All
commands starting with a : (colon) character puts vi in Last Line
Mode. When you press the colon (:) key on your keyboard the cursor
will move to the bottom left-hand side of the screen where you will
enter the command you want to execute. Unlike Command Mode commands,
you need to press the enter key on your keyboard to execute the Last
Line Mode commands.
The Last Line Mode command used to write your changes to disk and then
quit vi is:
:wq
To quit without writing your changes to disk, you would enter:
:q
If you did not make any changes during your editing session, vi will
return you to the shell prompt immediately. If you made changes during
your session, vi will inform you of this and ask you to confirm your
desire to quit without saving the changes. Adding a ! (exclamation
point) to the end of the quit command will inform vi that you want to
quit even though you haven't saved your changes:
:q!
As you have seen, pressing the colon (:) key will change the mode from
Command Mode to Last Line Mode. If you wanted to go from Last Line
Mode to Command Mode, you would just need to press the Esc key on your
keyboard.
HINT: If you are not sure about which mode you are
in, just press the Esc key on your keyboard a few times to verify you
are in Command Mode and go forward from there.
(3) Saving your Work Without Exiting (Quitting)
If you edit a file for a long period of time it would be a good idea
to save the work buffer's contents to disk occasionally.
The Last Line Mode command used to write your changes to disk without
quitting vi is:
:w
If you did not specify a filename when you started your vi editing
session, you could specify a file to save to using the following Last
Line Mode command:
:w filename
(4) Switching to Input Mode to Add Text
The only way to add text to the work buffer is by switching
from Command Mode to Input Mode. If text does not appear in the editor
as you type, you are not in Input Mode. There are a few different ways
to enter Input Mode.
Insert Mode
The first is by pressing the i key (lowercase i) to insert text. Text
will be inserted exactly where the cursor was when you pressed the i
key. If you enter an I (uppercase i), text will be inserted at the
start of the line the cursor is on.
Pressing the space bar on your keyboard will put a space between text,
and pressing the Backspace key on your keyboard will erase over what
you have typed. It is important to know that the Backspace key will
only erase text that is on the current line of the buffer (you can not
backspace up to the previous line of text). You also can only
backspace over text that was inserted during the current Input Mode
session.
Pressing the Enter key on your keyboard while in Insert Mode will
cause the cursor to advance to the next line. You should avoid letting
text lines automatically wrap from one line to the next by pressing
the Enter key before you get to the end of a line.
The Input Mode session ends when you press the Esc key on your
keyboard, which returns you to Command Mode. When you press the Esc
key the cursor will move to the left one position.
Append Mode
You can also enter Input Mode by pressing the a key (lowercase a) to
append text. Text will be appended one position to the right of where
the cursor was when you pressed the a key. If you enter an A
(uppercase a), text will be appended at the end of the line the cursor
is on.
Other
The last method we will cover for entering Input Mode is by pressing
the o key (lowercase o) to open a line for adding text below the line
the cursor is on. The cursor will be moved to the beginning of the
line and you are ready to enter text. If you enter an O (uppercase o),
a line for adding text will be opened above the line the cursor is
one. This would be useful if you wanted to add a new line of text to
the beginning of the buffer (file).
(5) Diagram of vi Editor Modes
This diagram shows the different vi editor modes of operation and the
methods for changing from one mode to another:
