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

March  1997

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)

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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)

:set all

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

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

The second version of yank will yank the current line plus the additional number of lines you request.

"dy2     (press RETURN)

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

"Ky13y      (or omit the second y and type RETURN)

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

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.

Resources

• Last month's Unix 101
  /sunworldonline/common/swol-backissues-columns.html#unix101
• Yahoo's http://www.yahoo.com/Computers_and_Internet/Software/Text_Ed itors/vi/
  http://www.yahoo.com/Computers_and_Internet/Software/Text_Editors/vi/
• The Association for Computing Machinery's vi manual pages
  http://teche.cacs.usl.edu/tutorial/unix-vi/tableofcontents3_2.html
• A vi tutorial
  http://www.wcmh.com/uworld/archives/95/tutorial/009/009.html
• The vi lovers home page
  http://www.cs.vu.nl/~tmgil/vi.html

About the author
Mo Budlong is president of King Computer Services, Inc. and has been involved in Unix development on Sun and other platforms for over 15 years. King Computer Services, Inc. specializes in Unix and client/server consulting and training and currently publishes the COBOL Just In Time Course, a crash course for the Year 2000 problem. Reach Mo at mo.budlong@sunworld.com.

If you have technical problems with this magazine, contact webmaster@sunworld.com

URL: http://www.sunworld.com/swol-03-1997/swol-03-unix101.html
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