Math 171 Spring 2005, Lab 2

Due Tuesday, January 25 11:59 P.M.

1. Overview
2. Editing Textfiles with vi
3. Vi Links
4. Assignment

Overview

This lab is intended to introduce you to vi, a programmer's text editor. While vi is much less intuitive to use than most other text editors, you will find that becoming proficient with vi allows you to perform common editing tasks more quickly.

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Editing textfiles with vi

• The most important thing to remember when editing files with vi is that unlike most other text editors, vi has a command mode and an insert mode. When you first start editing a file, you will be in command mode. Some vi commands place you in insert mode, allowing you to enter text. You can always return to command mode by hitting the escape key until you hear a beep or the screen flashes. You should also be aware that since vi is a console-mode text editor, you will not be able to use the mouse to position the cursor or scroll through text.
• Copy my lab2 directory into your home area using the command

  
  cp -R ~gbutler/m171/spring_2005/lab2 ~
  
  

  This directory should contain two files called practice and assignment.
• Begin editing the file practice by moving into the lab2 directory, and then typing vi, followed by the filename:

  
  cd ~/lab2
  vi practice
  
  

• Unless otherwise specified, you should make sure you are in command mode when entering any of the vi commands below. Also, make sure you pay attention to whether you enter commands in upper or lower case: for example, j and J are two different commands. Finally, note everything you should actually type into vi has been formatted using a red, fixed-width font.
• When you first start editing a file, the cursor should be located at the first row and column. Use the CTRL-G command to display your current position in the file.
• Practice moving around in the file for awhile using some of the motion commands in the following table:

  Command	Movement
  h	left one column
  l	right one column
  j	down one line
  k	up one line
  w	forward one word
  b	back one word
  {	move to start of paragraph
  }	move to end of paragraph
  (	move to start of sentence
  )	move to end of sentence
  $	end of the current line
  ^	first non-blank character on the current line
  |	start of current line
  %	move to matching parenthesis/curly brace/square bracket
  CTRL-F	forward one page
  CTRL-D	forward one-half of a page
  CTRL-B	back one page
  CTRL-U	back one-half of a page
  H	moves to first line currently visible on screen
  L	moves to last line currently visible on screen
  G	skips to end of file
  f<letter>	finds first occurence of <letter> to the right of the cursor on this line
  F<letter>	finds first occurence of <letter> to the left of the cursor on this line
  /<phrase>Enter	finds first occurence of <phrase> after cursor
  ?<phrase>Enter	finds first occurence of <phrase> before cursor
  n	skips to next occurrence of search phrase
  N	skips to previous occurrence of search phrase

• Most vi commands can be modified by preceding them with a number, which ususally has the effect of executing the command multiple times. One exception to this rule is the G command, which skips to the specified line when preceded by a number. For example, move to the ninth line of the file. Typing 5w will move forward 5 words, and typing 3fe will find the third occurrence of the letter e to the right of the cursor position. Practice combining various numbers with the motion commands listed above.
• Now we'll practice using insert mode. Return to the top of the file by typing 1G, followed by ^. Now move to the closing parenthesis five lines down by typing 5j, then f). Type i to enter insert mode. Type your name, and return to command mode by pressing the Escape key. There are several text entry commands, all of which place vi into insert mode. Try each of the text entry commands listed in the table below before proceeding to the next step.

  Text Entry Command	Purpose
  i	insert text before cursor on current line
  I	insert text at beginning of current line
  a	insert text after cursor on current line (i.e. append at cursor)
  A	insert text at end of current line (i.e. append to current line)
  o	insert text on new line below current
  O	insert text on new line above current

  As with motion commands, text entry commands may be preceded by a number to execute them repeatedly. For example, try moving to the fifth line of the file, then typing 5ohello, and then hitting the escape key. This will create five lines below the current one containing the word hello.
• Vi has several editing commands that can be used to quickly perform common text manipulations. For example, try moving to the line containing the phrase "This line should be joined". Merge this line with the next using the J command. Now make a copy of this line by typing yy, followed by p. Try some more of the editing commands in the table before continuing:

  Editing Command	Purpose	Places vi in insert mode?
  x	deletes character	no
  cc	overwrites entire line	yes
  dd	deletes line	no
  yy	copies line to buffer	no
  p	pastes buffer contents at current cursor position	no
  u	undo	no
  CTRL-R	redo	no
  .	repeat last editing command	no

• In addition to the editing commands listed above, vi has several editing commands that may be combined with motion commands to manipulate text. Typically, each of these commands is applied to the range of text between the current cursor position and the cursor position after the indicated motion command. For example, try moving the cursor to the beginning of the word 'extraneous'. The d command is used to delete text, so typing d5l deletes 5 letters to the right of the current cursor position, and typing d4w deletes the first four words after the cursor. Now move to the beginning of the next line. Typing 2fx moves to the second occurrence of the letter x on the line. The c command changes text, so typing c6fxtwo occurrences of , followed by the escape key, will change everything up to the sixth occurence of an x after the cursor to the phrase "two occurrences of ". Note how the editor indicates you are using insert mode after you finish typing the motion command. Lastly, go to the beginning of the next line and type !$date, followed by Enter. This takes all the text in the range of lines specified by the motion command and sends it to the shell command date, then replaces these lines by the shell command's output. The $ command does not change the current line, and date ignores its input and gives the current date and time as output. The result is that the current line is replaced by the current date and time. Try some more of the editing commands given in the table below before continuing. Note that all these commands must be followed by a motion command.

  Editing Command	Purpose	Places vi in insert mode?
  d	delete text	no
  c	change text	yes
  y	yank text to buffer	no
  !	prompts for shell command to filter text	no

• Vi's basic search and replace functionality is accessed by typing :g/.*/s/, followed by the search text, followed by /, followed by the replacement text, followed by /g, followed by Enter. For example, if I wanted to replace every occurrence of "Lenore" in the practice file with "Lenoir", I would type :g/.*/s/Lenore/Lenoir/g, then hit Enter. Vi uses a special type of language called a regular expression for describing text. Together with vi's search and replace, regular expressions provide a powerful text processing tool. See the link below for more information.
• Once you have finished practicing with vi, terminate your editing session using one or more of the following commands, followed by the Enter key.

  Command	Purpose
  :q	quits vi
  :q!	quits vi without saving current file
  :w	saves file
  :w <filename>	saves file as <filename>
  :w! <filename>	overwrites file as <filename>
  :wq	saves and quits
  :n	edit next file specified on command line
  :n!	edit next file specified on command line without saving current file
  :n <filename>	edit file named <filename>
  :n! <filename>	edit file named <filename> without saving current file

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Vi Links

• If you need a quick reference for vi commands, have a look at the Vi Cheat Sheet.
• If you want to get the most out of vi's search and replace facility, read Vim Regular Expressions 101.

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Assignment

• Edit the file assignment in your lab2 directory.
• Note that with the exception of part 1, there is a tedious way and a quick way to perform the requested editing.
• The file is divided into sections labeled ---PART 1---, ---PART 2---, etc. Each step below should be performed on the corresponding section of the file.
  1. I have written a few sentences about myself. Change these to describe yourself, and put all sentences on a single line.
  2. Edit this section to contain 1000 copies of the initial text.
  3. Replace the Gettysburg Address with the burial speech from Julius Caesar.
  4. Delete every word starting with a vowel.
  5. Justify this text to a maximum line width of 75 characters.
  6. Alphabetize this list of pizza toppings, and remove any extra blank lines.
• When you have finished the steps above, save your file and send it as an attachment to gbutler@math.utk.edu.

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