Grasping more of the vi editor
This reference
guide to basic, yet crucial vi commands continues with quick
methods for conducting searches, setting word wrapping margins,
and cutting, copying, and pasting text
Summary
The second of this two-part series on the vi editing tool
covers setting defaults for vi behavior and discusses how to
cut and paste using the yank command as well as cut and paste
across files. (2,500 words)
The response to part 1 of our
introduction to vi (the first Unix101 column) was terrific. I'm
glad that so many of you liked the article. There were a lot of
great suggestions -- some of which are included in this article,
and some of which I will save up for when we revisit vi in a
future column.
This article covers manipulating vi's default behavior and
cutting and pasting within as well as across files. Customizing
vi's behavior and learning to manage its buffers can greatly
improve its performance.
Vi's search function is a prime example of this. Searching is
done from command mode by typing a slash followed by the search
text as in:
/Encyclopedia
This will search for the string Encyclopedia. Once an
"Encyclopedia" is found, typing an "n" will
search for the next "Encyclopedia." Having grown
accustomed to PC editors that tend to default to a
case-independent search, vi annoyed me with the fact that
/Encyclopedia would find "Encyclopedia" but not
"encyclopedia" or "ENCYCLOPEDIA." Vi has a
setting that will cause the search to ignore case. This is an ex
mode command, so from command mode you type it as a colon
followed by ic as in:
:set ic (and press RETURN)
Ic is shorthand for ignorecase. If you need to turn this off
for a case-dependent search, type:
:set noic (and press RETURN)
Another useful set option is showmode. If you
tend to type and then break for something (research or a fresh
coffee), you might walk away from the computer leaving vi in
insert or edit mode.
:set showmode
will place a message in the last line of the screen on the
right indicating that you are in INSERT MODE, APPEND MODE, or
whatever.
This can be turned off with
:set noshowmode
To turn line numbering on and off use:
:set number
and
:set nonumber
Numbers are displayed at the beginning of each line. These
numbers do not appear in the document, simply on the screen.
They can be helpful if you are trying to compose something that
must fit in 55 lines (for a printed page).
Wrapping text
Setting the wrap margin will cause the text to auto wrap while
you are typing, but the command is quirky in a vi-ish sort of
way. The command is
:set wrapmargin=nn (where nn is a number)
The odd thing about this command is that it sets the amount
of space to the right that will not contain text. It would seem
natural to set wrapmargin=60 and assume that you would have 60
characters worth of space to type in, but wrapmargin=60 sets a
margin of 60, and you only have 20 characters in which to write.
To set margins determine the width of text you want on the
screen and use the formula
:set wrapmargin=(80 - text width)
You can see all of the :set options that are available by typing
:set all
A list of set options will be displayed that allow you to set
auto indenting, auto saving, word wrapping margins, how many
lines to scroll for CTRL-D and CTRL-U commands, and to set up
the editor to use defaults for certain programming languages.
You can issue set commands at the bottom of the screen while
you are editing, or you can set them up as defaults for your
personal vi use.
A file in your home directory named .exrc is a
vi initialization file that is loaded each time you run vi. You
may have one already, or you can create one using vi by changing
to your home directory and editing the file.
cd
vi .exrc
The set commands (without the leading colon) can be set up in
this file, and all of the options listed in .exrc
will be set each time you run vi.
Listing 1 is an example of an .exrc file. This .exrc
file sets vi up to use case-independent searches, to word wrap
at 65 characters (80-15), to show INSERT MODE at the bottom of
the screen when in insert mode, and to show line numbering. It
also changes the default scrolling of 12 lines for CONTROL-D or
CONTROL-U to 20 lines.
Listing 1 /home/mjb/.exrc - a vi initialization script
set ic
set wrapmargin=15
set showmode
set number
set scroll=20
Yanking data
Cut, copy, and paste are powerful vi commands. The commands can
also be used in a variety of different ways. The delete line
command (dd) actually cuts text into a temporary paste buffer.
This makes it very easy to do cut and paste. The paste buffer is
dumped (pasted back in to the text) using the `p' command.
Suppose you are typing a letter and you realize that you need
to move a 7 line paragraph. In command mode position the cursor
to the first line of the paragraph and type: 7dd
This will delete 7 lines. They are removed from the edit
buffer and saved in the delete buffer (sometimes called the
unnamed buffer). Now move the cursor to where you want the
paragraph to be placed and type
p
This will paste the contents of the delete buffer at the
current location starting on the line just below the cursor. The
delete buffer always contains the last deleted text (text
deleted using dd, x, or X), and "p" can always be used
to paste it. This provides a quick and simple cut and paste.
Copy and paste is more versatile. There are 26 copy buffers
named with the lower case letters a through z. You copy data
into the buffer by using the yank command.
The yank command has two main forms. One yanks only the
current line (the line is not truly yanked, it is copied to the
copy buffer). The second version of yank yanks the current line
plus the additional number of lines you request. Purists will
argue that there is much more that you can do with yank, and
this is true, but these two are enough to get a great deal of
work done. An example of the first version in command mode is:
"ayy
In this command, the letter "a" is the name of the
copy buffer to use, and the yy indicates that the current line
is to be yanked. There's no real explanation for the initial
double quote -- that's just the way vi is -- a bit obscure at
times. This command yanks the current line into buffer a.
The second version of yank will yank the current line plus
the additional number of lines you request.
"dy2 (press RETURN)
This yanks the current line plus the next two lines into buffer
d, a total of three lines.
The actual sequence of a yank command is double quote
followed by the lower case letter identifying the copy buffer to
use followed by a "y" and either a second
"y" to indicate this line only or a number to indicate
the number of lines to yank in addition to the current line.
When a number of lines is used, end the command by typing
RETURN. You can also end a multi-line yank by typing another y
as in
"y15y
If you use the lowercase letters a-z for a yank, the buffer is
overwritten with the information that is yanked. If you use
uppercase A-Z, the yanked information is appended to the buffer.
"Ky13y (or omit the second y and type RETURN)
This command will yank the current line and 13 additional lines
and add them to the end of any already existing text in buffer
k.
Where to?
Now that we have yanked all this text we need to paste it
somewhere. The command for pasting a buffer uses the quotes, the
buffer character and a "p" for paste.
"np
This command will paste the contents of buffer n to the line
below the current cursor position.
Copy and paste can also be used across multiple files. To do
that, we need to look at a couple more commands that you might
already know.
The first is write, which writes the current changes for the
file you are editing to disk. This command is:
:w
It saves all your editing so far. This is a useful command to
know as it can save you from losing work in embarrassing
crashes. Just type :w once in a while and your edits are written
back to your file.
The second command is edit, which allows you to open another
file for editing. This command is:
:e filename
Using these two commands, you can move back and forth between
two files without having to leave vi. When you exit vi the
contents of the copy buffers are lost, so being able to change
files while still in vi preserves the contents of the copy
buffers and lets you copy and paste across files.
Listings 2 and 3 are simple text files shown with line
numbers (:set number). The task is to copy paragraphs 1, 3, and
5 from file1.txt to file2.txt.
Listing 2: file1.txt
1 Now is the time for every good person to come
2 to the aid of the party.
3
4 A bird in the hand is worth two in the bush.
5
6 These are the times that try men's souls. The Metropolitan
7 Transit Authority, better know as the MTA has attempted to
8 levy a burdensome tax in the form of a subway increase.
9
10 There is more than one way to skin a cat, and more than
11 one way to cut and paste.
12
13 This is the fifth paragraph to be transported
14 across the inter-file boundary.
15
Listing 3: file2.txt
1 May the road rise to meet your feet
2 May the wind push you ahead.
3 May the devil not know you're in heaven
4 Til an hour after your dead.
5
Listing 4 contains the commands you will type to copy
paragraphs 1, 3, and 5 from file1.txt to file2.txt
Listing 4: Copy and paste across files
Command Explanation
vi file1.txt (RETURN) open file1.txt for editing
:1 (RETURN) move to line 1
"ay2y yank 3 lines (current line + 2) into buffer a
:6 (RETURN) move to line 6
"by3y yank 4 lines into buffer b
:13 (RETURN) move to line 13
"cy2y yank 3 lines into buffer c
:w (RETURN) save the current file (if you've edited it)
:e file2.txt (RETURN) start editing file2.txt
:$ (RETURN) move to the end of file2.txt
"ap paste in buffer a
:$ (RETURN) move to the end of file2.txt
"bp paste in buffer b
:$ (RETURN) move to the end of file2.txt
"cp paste in buffer c
:w (RETURN) save your work
:e file1.txt (RETURN) back to file1.txt
Listing 5 is the resulting new file2.txt
Listing 5: file2.txt after editing
1 May the road rise to meet your feet
2 May the wind push you ahead.
3 May the devil not know you're in heaven
4 Til an hour after your dead.
5
6 Now is the time for every good person to come
7 to the aid of the party.
8
9 These are the times that try men's souls. The Metropolitan
10 Transit Authority, better know as the MTA has attempted to
11 levy a burdensome tax in the form of a subway increase.
12
13 This is the fifth paragraph to be transported
14 across the inter-file boundary.
15
Another way to do this would be to use append style copying.
Listing 6 achieves the same result as listing 4.
Listing 6: Copy and paste across files using append style
Command Explanation
vi file1.txt (RETURN) open file1.txt for editing
:1 (RETURN) move to line 1
"ay2y yank 3 lines (current line + 2) into buffer a
:6 (RETURN) move to line 6
"Ay3y append 4 lines into buffer a
:13 (RETURN) move to line 13
"Ay2y append 3 lines into buffer a
:w (RETURN) save the current file (if you've edited it)
:e file2.txt (RETURN) start editing file2.txt
:$ (RETURN) move to the end of file2.txt
"ap paste in buffer a
:w (RETURN) save your work
:e file1.txt (RETURN) back to file1.txt
The :e command has a memory and uses the symbol # to stand
for the name of the last file edited. In both listing 4 and 6,
the last line could have been:
:e # (RETURN)
The delete finale
Now that you know how to paste, we can take a further
interesting look at the delete command. I mentioned that deleted
text was placed in the unnamed buffer. There are actually 10
delete buffers that are given the names 0 through 9. Buffers 0
and 1 can be thought of as the same buffer. When you delete any
text it is stored in buffer 0. The contents of buffer 8 are
copied into buffer 9, buffer 7 is copied to 8, 6 to 7, and so
on. Finally buffer 0 is copied to buffer 1. This isn't exactly
how it happens, but it is easiest to think of it this way.
Remembering that the unnamed buffer is buffer 0, and buffer 1 is
a copy of buffer 0, at any point while you are in command mode,
you have the following commands available to you that allow you
to paste previous deletions back into the file.
Command Effect
p Paste the last deletion into the text
"0p Paste the last deletion into the text
"1p Paste the last deletion into the text
"2p Paste the 2nd to last deletion into the text
"3p Paste the 3rd to last deletion into the text
"4p Paste the 4th to last deletion into the text
"5p Paste the 5th to last deletion into the text
"6p Paste the 6th to last deletion into the text
"7p Paste the 7th to last deletion into the text
"8p Paste the 8th to last deletion into the text
"9p Paste the 9th to last deletion into the text
This gives you a powerful range of options for cut and paste
as well as copy and paste. Cut and paste will work across files
just as copy and paste does.
The delete buffers also give you 9 levels of undo on line
deletions.
I have only scratched the surface of vi. There are of course
complex search and replace commands, macros, quick methods of
substituting and copying text, methods of copying an entire file
into the file you are editing, or ways of executing a shell
command and having the output of the command added to your edit
buffer. You can also edit multiple files one after the other and
move between them quickly. Look for these in a future article
when I will have a chance to revisit vi.
Meanwhile I'd love to hear from you about what you would like
to see in future Unix 101 columns.
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