This chapter introduces the vi editor and describes how to get
started using it. Although the vi editor is not the most friendly nor easiest to
use editor, it is found on almost all Unix systems. Thus, it is worthwhile to at
least become familiar with this editor so that you will have an editing tool you can use should you find yourself on a system which lacks your favorite editor.
vi
is a full-screen editor which can be used to
create and edit files in Unix environments.
Several books describe use of the vi editor and many
of the general books about Unix contain a section describing its use.
Manual pages for vi are available online and may be viewed using the
man command. A summary of the most commonly used vi commands is
included in Vi Command Key Summary and a more
comprehensive tabulation of vi commands is available in
Vi Commands.
vi is very different from most other editors -- the typewriter keys
are used both to enter text and to enter commands.
Since the vi command structure is not intuitive for most people,
several practice editing sessions may be required before you will feel
comfortable using its commands.
The basic commands provided within this users guide should provide you
with enough information to begin editing files productively with a
minimum of frustration.
Beginning vi
To begin editing a file, simply enter:
vi file_name
where "file_name" is the name of the file you wish to edit or create.
If you are not placed in full screen mode when you begin vi, it
is likely that the TERM environmental variable has not been set
correctly for full screen terminal emulation mode. The Unix
env command
(or the command printenv in some environments) can be used to display a list of
the current environmental variables.
If you are unsure what type of terminal emulation you should use,
try vt100 first as it is supported by a variety of machines.
See Defining the Terminal Type
for details of reassigning the value of the
TERM environmental variable.
vi Modes
The three primary modes in vi are: command mode, input mode, and
lastline mode.
When you begin editing a file in vi, you will be in command mode. Any
key you press will issue a command which enables you to move to a
specific location in the file, open a new line, read in an external
file, delete text, or begin entering new text.
Cursor Movement Keys
When you are in command mode on
many Unix systems, the cursor (or arrow)
keys will enable you to move from one location to another in the file.
If they do not function, you can still move around in the file using the
default movement keys which are located in the "hjkl" row on the right hand side of the keyboard.
You should be familiar with these keys so that
you will be prepared should you log onto a Unix system and find that
the cursor arrow keys are not functional on that system:
<h> move the cursor left
<j> move the cursor down
<k> move the cursor up
- <l> move the cursor right
Note:
You will also need to be familiar with these keys if
you wish to use vi for command line recall and editing capabilities of
the Korn Shell.
vi remains in command mode when the above commands are entered.
Observe that these key assignments are keyboard positional and not
mnemonic; i.e., pressing the <l> key located in the right-most position
of the "hjkl" row moves the cursor right and not left. Likewise, the
<h> key moves the cursor to the left.
The <j> and <k> keys move the
cursor down and up respectively.
If you attempt to move the cursor
above the top line on the
screen or below the bottom line, the screen will scroll upwards
or downwards so that new text lines appear.
Scrolling stops when the top or bottom of
the file is encountered. As an aid to remember which key performs the down function, note that
the tail of the letter "j" extends down below the current line.
Most vi commands can be preceded by a number which results in the command
being performed for the specified number of units, e.g.,
entering the command "9j" will result
in the cursor moving down 9 lines.
This capability
is very powerful as it enables you to move rapidly within a file with
a minimum of key strokes.
Input Mode
From command mode, press the <o> key
to add a blank line below the line
containing the cursor; press <O> (capital "o")
to add a line above the current line.
After entering either of the above commands, vi will be in input mode
which enables you to enter text.
Press the <Esc> key whenever you wish to
return to command mode. If you are ever unsure if you are in command
mode, press the <Esc> key twice.
Pressing the <Esc> once will usually be sufficient, but pressing it
twice will guarantee that you are in command mode.
Pressing the <Return> key while in input mode when at the end of a line
can also be used to open a new line for entering text.
If you press the
<Return> key in the middle of a line while in input mode, you
will split the line at the cursor position.
You will remain
in input mode after either of these operations.
The following commands can also be used to enter input mode:
<i> begin entering text immediately in front of the cursor
<I> begin entering text at the beginning of the line
<a> begin entering text immediately after the cursor
<A> begin entering text at the end of the line
While in input mode, the cursor keys may
not function as
expected. Press <Esc> to return to command mode in order to move
about in your file.
Keyboard Mappings
describes how you can map the cursor keys so that
they will function in input mode as well as in command mode.
To join two lines together, press <Esc> twice
to guarantee that you are in
command mode, locate
the cursor anywhere
within the uppermost line and press the "J" key.
The cursor need not be placed at the end of the line.
While in input mode, you may be able to
delete the character to the left of the
cursor by pressing the <Del> or <Backspace> key.
Using Command and Lastline Modes
The <Esc> key is used to return to command mode.
You may press the <Esc> key additional times; on most
systems you will simply hear a beep if you were already in command mode.
When in doubt, press: <Esc>
Exiting From vi
To save your changes and
exit from vi, enter "ZZ" or ":wq"
from command mode. If you wish to quit without
saving, enter ":q!" instead.
The command ":q" can be used to
quit from a file if no changes have been made.
Note: Commands
such as ":wq" and ":q!"
are lastline ("ed" or "ex" editor) commands which
are supported by vi. Lastline commands are invoked from command mode
by entering the character ":" followed by the desired command.
Correcting Mistakes
vi includes an undo feature. Providing you have not moved from
the line where the last change was made, you can enter the "u" command
to undo the last change; entering the "U" command will undo all changes
made since you had moved to the current line.
Modifying Text
To change (replace) a single character, enter the letter "r" from command
mode followed by the new character; to begin replacing characters from
the current cursor position to the end of the line, enter the vi
command "R". Press <Esc> to return to command mode.
To delete a character, press <Esc> twice
to guarantee that you are in command
mode, move the cursor to the character you wish to delete, and then
press "x".
Use the command "dw" to delete from the cursor position to the
end of the word; to
delete an entire
word, place the cursor on the first character of the word
and enter "dw".
Use the "D" command to erase all
text from the current cursor position to the end of the line.
To delete a line of text, enter the command "dd"; to delete 9 lines
of text downward beginning with the line containing the cursor, enter
the command "9dd".
To move a set of lines, first delete them, then move to the
line below which you wish to move the text and
enter the paste command "p".
To copy a line, instead of moving it, yank it into a
buffer using the "yy" command,
move to the new location, and
enter the command "p".
As in the procedure
used for deleting
lines, you can precede the yank command with a number to
indicate how many lines should be included in the yank buffer.
To find a text string which occurs in the file
after the current cursor position (forward search),
enter a slash (/) followed by the string of text you would like to
locate. Use the "n" command to locate the next occurrence of the
text string.
To change every occurrence of a specific string, enter:
:%s/old string/new string/g
where old string is the original string which is to be changed
and new string is the new text you wish to substitute.
The "%" indicates that the action is to be performed for
the whole work buffer. The range within which changes are to be made
can be restricted by specifying an address of lines instead of "%".
For example, to change all occurrences of the text string in lines
12 to 27, substitute "12,27" for "%" in the previous example.
The letter g in the example
is used to indicate that a global
change (all occurrences) within the specified range is desired.
To perform a selective change, that is, to verify each change before it
is made, use "gc" instead of "g" in the change command
illustrated above.
Enter "y" to make the change at the current cursor position, press
<Return> to leave the text unchanged and move to the next occurrence
of the "old text" string specified by the change command.
You can press <Ctrl-C> to terminate the selective change prior to reaching
the last occurrence of the text within the file.
Merging Files
Enter the command
:r filespec to merge another file into the one currently
being edited.
The merged text will be placed below the line containing the cursor.
Changing the Default vi Environment
The file .exrc, located in your home directory,
contains commands which define your default processing
environment for "vi". This file may include set commands to specify
file processing options, keyboard mappings, and abbreviations.
These commands can also be invoked as lastline commands by entering
the character ":" while in command mode and then typing in the command
you wish to invoke.
The set command is used to define the general environment.
Some of the most commonly used set options include:
- showmode
- enables a message in the lower right corner indicating
when the program is in INPUT or REPLACE mode; no message is displayed
when the editor is in command mode.
- number
- results in a display of the line numbers along the left
margin.
- wm=2
- sets the wrapmargin at two characters from the right margin.
This command enables wordwrap at the right margin.
- list
- results in the display of hidden characters such as control
sequences and new line.
The above options could be defined by individual set commands, or
by entering the following while in command mode:
:set showmode number wm=2 list
All of the above options may not be available in the implementation of
vi provided with your operating system.
To display
a list of the possible configuration options available on your system
and their current settings,
enter the following from command mode:
:set all
Note: Although the values of the set variable can be defined in the
environmental variable EXINIT, it is recommended that you avoid using
this variable and define the vi settings you would like to use in the
file ".exrc". On some systems,
the presence of the environmental variable EXINIT
inhibits invocation of the definitions stored in ".exrc".
Commands can be assigned to any of the keyboard characters, however, it
is advised that you not use the keys which are assigned functions by
vi itself.
Safe keys to use for assigning commands are the function
(F) keys, and when in command mode: <Ctrl-A>, <Ctrl-C>, <Ctrl-I>
<Ctrl-K>,
<Ctrl-O>,
<Ctrl-T>, <Ctrl-W>, <Ctrl-X>,
@, #, *, \, g, q, v, K, V, and Z.
The <Ctrl-V> key sequence is used to quote the function of
a key so that the escape sequence generated by the key can be used in
a keyboard map definition. For example, to include the sequence
which would be generated when the <Return> key is pressed as part of
a map definition, press the sequence <Ctrl-V><Return>.
To assign a
map definition to a key, type the command "map"
followed by a space, press
the key sequence to which you would like to assign a
command, and then enter the command you would like to have executed by
this key. Include <Ctrl-V> before any key sequences which must be
disabled in order to be included in the definition.
For example, to assign the equivalent of the Xedit Quit command (exit
from the file if no changes have been made) to the command mode
F3 key, enter:
map <Ctrl-V><F3> " <Ctrl-V><Return>
You can also use "map!" instead of "map" to assign
a command to a function key or arrow key when in insert mode.
If you would like to assign the "quit" command to the "F3" key in
input mode as well as in
command mode, duplicate the above map command and include an
exclamation point following the word "map" and an <Esc> key sequence
to return to command mode prior to issuing the """ command:
map! <Ctrl-V><F3> <Ctrl-V><Esc>" <Ctrl-V><Return>
To assign the sequence <Esc> "h" "a" (i.e., go into
command mode, use the vi "h" command to move the cursor
to the right, and then execute
the vi "a" command which places you in insert mode after the cursor)
to the LeftArrow key, include
the following line in your ".exrc" file:
map! <Ctrl-V><LeftArrow> <Ctrl-V><Esc>ha
Once this has been done, you need no longer be concerned about whether
you are or are not in insert mode when you press the left arrow key.
If you are in input mode, the definition
assigned by the "map!" command will be used; if
you are in command mode, the default definition or that assigned by
the map command will be used.
The remaining arrow keys could be assigned functions in a similar
fashion.
Note: Keyboard mappings are terminal dependent, and must be
entered from the terminal you will be using -- see the documentation for
your ssh client for infomation on keyboard mappings.
The :ab command can be included in the ".exrc" file to assign text
strings so that you can enter the abbreviation and have it expanded to
the full text string by the editor. For example, suppose you
frequently make reference to "Virginia Tech" within your writing. This
phrase
could be assigned the abbreviation VT by inclusion of the following
line in your ".exrc" file:
:ab VT Virginia Tech
vi Command Key Summary
The following table summarizes the most commonly used vi commands:
- Entering Text: a, A, i, I, o, and O
- Cursor Movement: h, j, k, and l
- Deleting Text and Lines: x and dd
- Copying Text: yy and then p
- Undo Changes: u and U
- Searching for Specific Text: / and ?
- Exiting vi:
- :wq or ZZ command to save changes and exit
- "! command to quit without saving changes
Note: You must be in command mode (press <Esc> twice
if in doubt) to issue
any of the commands in this table.
If you are logging onto a remote Unix system and vi appears to behave
erratically, you can use the <Ctrl-L> key sequence to redraw the screen.
For a more comprehensive tabulation of vi commands, see:
Vi Commands.
| 