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An Introduction to Display Editing with Vi USD:11-1

An Introduction to Display Editing with Vi William Joy Mark Horton Computer Science Division Department of

Electrical Engineering and Computer Science University of California, Berkeley Berkeley, Ca. 94720

Vi (visual) is a display oriented interactive text editor. When using vi the screen of your terminal acts as a

window into the ﬁle which you are editing. Changes which you make to the ﬁle are reﬂected in what you see.

Using vi you can insert new text any place in the ﬁle quite easily. Most of the commands to vi move the cur-

sor around in the ﬁle. There are commands to move the cursor forward and backward in units of characters, words,

sentences and paragraphs. A small set of operators, like d for delete and c for change, are combined with the motion

commands to form operations such as delete word or change paragraph, in a simple and natural way. This regularity

and the mnemonic assignment of commands to keys makes the editor command set easy to remember and to use.

Vi will work on a large number of display terminals, and new terminals are easily driven after editing a termi-

nal description ﬁle. While it is advantageous to have an intelligent terminal which can locally insert and delete lines

and characters from the display, the editor will function quite well on dumb terminals over slow phone lines. The

editor makes allowance for the low bandwidth in these situations and uses smaller window sizes and different dis-

play updating algorithms to make best use of the limited speed available.

It is also possible to use the command set of vi on hardcopy terminals, storage tubes and ‘‘glass tty’s’’ using a

one line editing window; thus vi’s command set is available on all terminals. The full command set of the more tra-

ditional, line oriented editor ex is available within vi; it is quite simple to switch between the two modes of editing.

1. Getting started

This document provides a quick introduction to vi. (Pronounced vee-eye.) You should be running vi on a ﬁle

you are familiar with while you are reading this. The ﬁrst part of this document (sections 1 through 5) describes the

basics of using vi. Some topics of special interest are presented in section 6, and some nitty-gritty details of how the

editor functions are saved for section 7 to avoid cluttering the presentation here.

There is also a short appendix here, which gives for each character the special meanings which this character

has in vi. Attached to this document should be a quick reference card. This card summarizes the commands of vi in

a very compact format. You should have the card handy while you are learning vi.

1.1. Specifying terminal type

Before you can start vi you must tell the system what kind of terminal you are using. Here is a (necessarily

incomplete) list of terminal type codes. If your terminal does not appear here, you should consult with one of the

staff members on your system to ﬁnd out the code for your terminal. If your terminal does not have a code, one can

be assigned and a description for the terminal can be created.

Code Full name Type

2621 Hewlett-Packard 2621A/P Intelligent

2645 Hewlett-Packard 264x Intelligent

act4 Microterm ACT-IV Dumb

act5 Microterm ACT-V Dumb

adm3a Lear Siegler ADM-3a Dumb

adm31 Lear Siegler ADM-31 Intelligent

c100 Human Design Concept 100 Intelligent

dm1520 Datamedia 1520 Dumb

dm2500 Datamedia 2500 Intelligent

dm3025 Datamedia 3025 Intelligent

fox Perkin-Elmer Fox Dumb

h1500 Hazeltine 1500 Intelligent

h19 Heathkit h19 Intelligent

i100 Infoton 100 Intelligent

The ﬁnancial support of an IBM Graduate Fellowship and the National Science Foundation under grants

MCS74-07644-A03 and MCS78-07291 is gratefully acknowledged.

-- --

USD:11-2 An Introduction to Display Editing with Vi

mime Imitating a smart act4 Intelligent

t1061 Teleray 1061 Intelligent

vt52 Dec VT-52 Dumb

Suppose for example that you have a Hewlett-Packard HP2621A terminal. The code used by the system for

this terminal is ‘2621’. In this case you can use one of the following commands to tell the system the type of your

terminal:

% setenv TERM 2621

This command works with the csh shell. If you are using the standard Bourne shell sh then you should give the

commands

$ TERM=2621

$ export TERM

If you want to arrange to have your terminal type set up automatically when you log in, you can use the tset

program. If you dial in on a mime , but often use hardwired ports, a typical line for your .login ﬁle (if you use csh)

would be

setenv TERM `tset − −d mime`

or for your .proﬁle ﬁle (if you use sh)

TERM=`tset − −d mime`

Tset knows which terminals are hardwired to each port and needs only to be told that when you dial in you are prob-

ably on a mime . Tset is usually used to change the erase and kill characters, too.

1.2. Editing a ﬁle

After telling the system which kind of terminal you have, you should make a copy of a ﬁle you are familiar

with, and run vi on this ﬁle, giving the command

% vi name

replacing name with the name of the copy ﬁle you just created. The screen should clear and the text of your ﬁle

should appear on the screen. If something else happens refer to the footnote.‡

1.3. The editor’s copy: the buffer

The editor does not directly modify the ﬁle which you are editing. Rather, the editor makes a copy of this ﬁle,

in a place called the buffer, and remembers the ﬁle’s name. You do not affect the contents of the ﬁle unless and until

you write the changes you make back into the original ﬁle.

1.4. Notational conventions

In our examples, input which must be typed as is will be presented in bold face. Text which should be

replaced with appropriate input will be given in italics. We will represent special characters in SMALL CAPITALS.

‡ If you gav e the system an incorrect terminal type code then the editor may have just made a mess out of your screen.

This happens when it sends control codes for one kind of terminal to some other kind of terminal. In this case hit the keys

:q (colon and the q key) and then hit the RETURN key. This should get you back to the command level interpreter. Figure

out what you did wrong (ask someone else if necessary) and try again.

Another thing which can go wrong is that you typed the wrong ﬁle name and the editor just printed an error diagnostic.

In this case you should follow the above procedure for getting out of the editor, and try again this time spelling the ﬁle

name correctly.

If the editor doesn’t seem to respond to the commands which you type here, try sending an interrupt to it by hitting the

DEL or RUB key on your terminal, and then hitting the :q command again followed by a carriage return.

-- --

An Introduction to Display Editing with Vi USD:11-3

1.5. Arrow keys

The editor command set is independent of the terminal you are using. On most terminals with cursor position-

ing keys, these keys will also work within the editor. If you don’t hav e cursor positioning keys, or even if you do,

you can use the hjkand l keys as cursor positioning keys (these are labelled with arrows on an adm3a).*

(Particular note for the HP2621: on this terminal the function keys must be shifted (ick) to send to the

machine, otherwise they only act locally. Unshifted use will leave the cursor positioned incorrectly.)

1.6. Special characters: ESC, CR and DEL

Several of these special characters are very important, so be sure to ﬁnd them right now. Look on your

keyboard for a key labelled ESC or ALT. It should be near the upper left corner of your terminal. Try hitting this key

a few times. The editor will ring the bell to indicate that it is in a quiescent state.‡ Partially formed commands are

cancelled by ESC, and when you insert text in the ﬁle you end the text insertion with ESC. This key is a fairly harm-

less one to hit, so you can just hit it if you don’t know what is going on until the editor rings the bell.

The CR or RETURN key is important because it is used to terminate certain commands. It is usually at the right

side of the keyboard, and is the same command used at the end of each shell command.

Another very useful key is the DEL or RUB key, which generates an interrupt, telling the editor to stop what it is

doing. It is a forceful way of making the editor listen to you, or to return it to the quiescent state if you don’t know

or don’t like what is going on. Try hitting the ‘/’ key on your terminal. This key is used when you want to specify a

string to be searched for. The cursor should now be positioned at the bottom line of the terminal after a ‘/’ printed as

a prompt. You can get the cursor back to the current position by hitting the DEL or RUB key; try this now.* From

now on we will simply refer to hitting the DEL or RUB key as ‘‘sending an interrupt.’’**

The editor often echoes your commands on the last line of the terminal. If the cursor is on the ﬁrst position of

this last line, then the editor is performing a computation, such as computing a new position in the ﬁle after a search

or running a command to reformat part of the buffer. When this is happening you can stop the editor by sending an

interrupt.

1.7. Getting out of the editor

After you have worked with this introduction for a while, and you wish to do something else, you can give the

command ZZ to the editor. This will write the contents of the editor’s buffer back into the ﬁle you are editing, if you

made any changes, and then quit from the editor. You can also end an editor session by giving the command :q!CR;†

this is a dangerous but occasionally essential command which ends the editor session and discards all your changes.

You need to know about this command in case you change the editor’s copy of a ﬁle you wish only to look at. Be

very careful not to give this command when you really want to save the changes you have made.

2. Moving around in the ﬁle

2.1. Scrolling and paging

The editor has a number of commands for moving around in the ﬁle. The most useful of these is generated by

hitting the control and D keys at the same time, a control-D or ‘ˆD’. We will use this two character notation for

referring to these control keys from now on. You may have a key labelled ‘ˆ’ on your terminal. This key will be

represented as ‘↑’ in this document; ‘ˆ’ is exclusively used as part of the ‘ˆx’ notation for control characters.‡

* As we will see later, h moves back to the left (like control-h which is a backspace), j moves down (in the same column),

k moves up (in the same column), and l moves to the right.

‡ On smart terminals where it is possible, the editor will quietly ﬂash the screen rather than ringing the bell.

* Backspacing over the ‘/’ will also cancel the search.

** On some systems, this interruptibility comes at a price: you cannot type ahead when the editor is computing with the

cursor on the bottom line.

† All commands which read from the last display line can also be terminated with a ESC as well as an CR.

‡ If you don’t hav e a ‘ˆ’ key on your terminal then there is probably a key labelled ‘↑’; in any case these characters are one

and the same.

-- --

USD:11-4 An Introduction to Display Editing with Vi

As you know now if you tried hitting ˆD, this command scrolls down in the ﬁle. The D thus stands for down.

Many editor commands are mnemonic and this makes them much easier to remember. For instance the command to

scroll up is ˆU. Many dumb terminals can’t scroll up at all, in which case hitting ˆU clears the screen and refreshes it

with a line which is farther back in the ﬁle at the top.

If you want to see more of the ﬁle below where you are, you can hit ˆE to expose one more line at the bottom

of the screen, leaving the cursor where it is. The command ˆY (which is hopelessly non-mnemonic, but next to ˆU

on the keyboard) exposes one more line at the top of the screen.

There are other ways to move around in the ﬁle; the keys ˆF and ˆB move forward and backward a page, keep-

ing a couple of lines of continuity between screens so that it is possible to read through a ﬁle using these rather than

ˆD and ˆU if you wish.

Notice the difference between scrolling and paging. If you are trying to read the text in a ﬁle, hitting ˆF to

move forward a page will leave you only a little context to look back at. Scrolling on the other hand leaves more

context, and happens more smoothly. You can continue to read the text as scrolling is taking place.

2.2. Searching, goto, and previous context

Another way to position yourself in the ﬁle is by giving the editor a string to search for. Type the character /

followed by a string of characters terminated by CR. The editor will position the cursor at the next occurrence of this

string. Try hitting n to then go to the next occurrence of this string. The character ? will search backwards from

where you are, and is otherwise like /.†

If the search string you give the editor is not present in the ﬁle the editor will print a diagnostic on the last line

of the screen, and the cursor will be returned to its initial position.

If you wish the search to match only at the beginning of a line, begin the search string with an ↑. To match

only at the end of a line, end the search string with a $. Thus /↑searchCR will search for the word ‘search’ at the

beginning of a line, and /last$CR searches for the word ‘last’ at the end of a line.*

The command G, when preceded by a number will position the cursor at that line in the ﬁle. Thus 1G will

move the cursor to the ﬁrst line of the ﬁle. If you give G no count, then it moves to the end of the ﬁle.

If you are near the end of the ﬁle, and the last line is not at the bottom of the screen, the editor will place only

the character ‘˜’ on each remaining line. This indicates that the last line in the ﬁle is on the screen; that is, the ‘˜’

lines are past the end of the ﬁle.

You can ﬁnd out the state of the ﬁle you are editing by typing a ˆG. The editor will show you the name of the

ﬁle you are editing, the number of the current line, the number of lines in the buffer, and the percentage of the way

through the buffer which you are. Try doing this now, and remember the number of the line you are on. Give a G

command to get to the end and then another G command to get back where you were.

You can also get back to a previous position by using the command `` (two back quotes). This is often more

convenient than G because it requires no advance preparation. Try giving a G or a search with / or ? and then a `` to

get back to where you were. If you accidentally hit n or any command which moves you far away from a context of

interest, you can quickly get back by hitting ``.

2.3. Moving around on the screen

Now try just moving the cursor around on the screen. If your terminal has arrow keys (4 or 5 keys with arrows

going in each direction) try them and convince yourself that they work. If you don’t hav e working arrow keys, you

can always use h, j, k, and l. Experienced users of vi prefer these keys to arrow keys, because they are usually right

underneath their ﬁngers.

† These searches will normally wrap around the end of the ﬁle, and thus ﬁnd the string even if it is not on a line in the di-

rection you search provided it is anywhere else in the ﬁle. You can disable this wraparound in scans by giving the com-

mand :se nowrapscanCR, or more brieﬂy :se nowsCR.

*Actually, the string you give to search for here can be a regular expression in the sense of the editors ex (1) and ed(1). If

you don’t wish to learn about this yet, you can disable this more general facility by doing :se nomagicCR; by putting this

command in EXINIT in your environment, you can have this always be in effect (more about EXINIT later.)

-- --

An Introduction to Display Editing with Vi USD:11-5

Hit the + key. Each time you do, notice that the cursor advances to the next line in the ﬁle, at the ﬁrst non-

white position on the line. The − key is like + but goes the other way.

These are very common keys for moving up and down lines in the ﬁle. Notice that if you go off the bottom or

top with these keys then the screen will scroll down (and up if possible) to bring a line at a time into view. The

RETURN key has the same effect as the + key.

Vi also has commands to take you to the top, middle and bottom of the screen. H will take you to the top

(home) line on the screen. Try preceding it with a number as in 3H. This will take you to the third line on the

screen. Many vi commands take preceding numbers and do interesting things with them. Try M, which takes you

to the middle line on the screen, and L, which takes you to the last line on the screen. L also takes counts, thus 5L

will take you to the ﬁfth line from the bottom.

2.4. Moving within a line

Now try picking a word on some line on the screen, not the ﬁrst word on the line. move the cursor using

RETURN and − to be on the line where the word is. Try hitting the w key. This will advance the cursor to the next

word on the line. Try hitting the b key to back up words in the line. Also try the e key which advances you to the

end of the current word rather than to the beginning of the next word. Also try SPACE (the space bar) which moves

right one character and the BS (backspace or ˆH) key which moves left one character. The key h works as ˆH does

and is useful if you don’t hav e a BS key. (Also, as noted just above, l will move to the right.)

If the line had punctuation in it you may have noticed that that the w and b keys stopped at each group of

punctuation. You can also go back and forwards words without stopping at punctuation by using W and B rather

than the lower case equivalents. Think of these as bigger words. Try these on a few lines with punctuation to see

how they differ from the lower case w and b.

The word keys wrap around the end of line, rather than stopping at the end. Try moving to a word on a line

below where you are by repeatedly hitting w.

2.5. Summary

SPACE advance the cursor one position

ˆB backwards to previous page

ˆD scrolls down in the ﬁle

ˆE exposes another line at the bottom

ˆF forward to next page

ˆG tell what is going on

ˆH backspace the cursor

ˆN next line, same column

ˆP previous line, same column

ˆU scrolls up in the ﬁle

ˆY exposes another line at the top

+ next line, at the beginning

− previous line, at the beginning

/ scan for a following string forwards

? scan backwards

B back a word, ignoring punctuation

G go to speciﬁed line, last default

H home screen line

M middle screen line

L last screen line

W forward a word, ignoring punctuation

b back a word

e end of current word

n scan for next instance of / or ? pattern

w word after this word

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