1. Chapter Three
The UNIX Editors

2. Lesson A
The vi Editor

3. Objectives Describe an ASCII text file
Explain why operating system editors use ASCII files
Create and edit simple documents using the vi editor

4. Understanding UNIX Files
Almost everything you create in UNIX is stored in a file
All information stored in files is in the form of binary digits
Binary digits are also known as bits
Bits have two states: 1 (on) and 0 (off)
0’s and 1’s as a way to communicate with a computer is known as machine language

5. Understanding UNIX Files
Machine language (or bit combinations) is translated into plain English using ASCII
ASCII stands for American Standard Code for Information Interchange
ASCII uses a byte (a string of 8 bits) to represent keyboard characters such as letters and numbers
Text files contain printable, ASCII characters
Binary files contain nonprintable characters, or machine language

7. Understanding UNIX Files
Programmers develop source code for their programs as text files which are compiled before being executed
Programmers also create scripts which are files containing commands. Scripts are not compiled, rather executed through an interpreter at run time
Executable Program Files are compiled and interpreted files that can be run on the computer to cause actions to be taken

8. Using Editors Editors let you create and edit ASCII files
UNIX normally includes two editors:
vi and emacs
vi and emacs are screen editors:
they display the text you are creating (or editing) one screen at a time

9. Using the vi Editor
Called vi because it is visual – it immediately displays on screen the changes that you make to text
It is also modal – works in three modes
Insert mode - lets you enter text
Command mode - lets you enter commands to perform editing tasks
Extended (ex) command set mode - lets you use an extended set of editing commands

10. Using the vi Editor
To create a new file in the vi editor, type vi and the name of the new file at the command prompt

11. Using the vi Editor When started, the vi editor is in command mode
In order to insert text, you must issue the “i” command to enter insert mode
You can repeat the line just entered with the repeat command (.)
To edit what you’ve just typed, move the cursor with the various keyboard cursor movement keys

12. Using the vi Editor
In insert mode, every character you type appears on the screen

13. Using the vi Editor
The repeat command repeats the last insertion, or line. Now, edit the new line in order to create the next item

14. Using the vi Editor

15. Using the vi Editor While still in command mode:
To delete text, move to a character and then type “x”
You can undo a command (reverse its effects) by typing “u”
To search for a text pattern, type a forward slash (/), type the pattern, and press Enter

16. Using the vi Editor

17. Using the vi Editor
Use the delete commands and the cursor movement keys to edit the text

18. Using the vi Editor

19. Using the vi Editor

20. Using the vi Editor
The status line at the bottom of the screen displays information, including line-oriented commands and error messages

21. Using the vi Editor
During text searches, you can replace, too. Use line-oriented commands in ex mode to perform this action

22. Using the vi Editor Saving a File and Exiting vi
You should always save the file before exiting vi, otherwise changes are lost
To save a file and continue working on it, type the :w (write) command
While in command mode, use the :wq (write and quit) command to save and exit, or the :zz command to exit after saving

23. Using the vi Editor In vi, you can also: Add text from another file
Leave vi temporarily to perform other UNIX tasks, then return to your file
Change your display while editing, such as adding line numbering to help editing
Copy, cut, and paste text to help editing
Print text files
Cancel an editing session

24. Using the vi Editor

25. Using the vi Editor

26. Lesson B
The Emacs Editor

27. Objectives
Compare and contrast the features of Emacs and the vi editor
Become familiar with the most important Emacs editor commands
Create and edit simple documents using Emacs editor

28. Using the Emacs Editor
More complex than vi, so not as popular, but it is more consistent and most commands begin with Alt or Ctrl key combinations
It is not modal like vi
Supports a sophisticated macro language and lets you extend beyond the Emacs program and read , for instance
Emacs is reputed to have more features than any other UNIX program

31. Using the Emacs Editor Creating a New File in Emacs
Type the Emacs command with the name of the new file after it at the command line
If you are using the GNOME interface, start Emacs by clicking the Main Menu icon, clicking Programs, clicking Applications, and then clicking Emacs

32. Using the Emacs Editor
The Emacs editor opens in a GUI, with menus containing command choices

33. Using the Emacs Editor
Notice the extensive command choices within the menu structure

34. Using the Emacs Editor
To save and exit, perform these key sequences: Ctrl+x and Ctrl+s to save, then Ctrl+x and Ctrl+c to exit

35. Using the Emacs Editor Editing an Emacs File
To navigate the cursor location, use the arrow keys, or Ctrl key combinations
Text is inserted by typing
Ctrl+x and then “u” is the undo command
You can cut, copy and paste text
There is a text search feature as well
Emacs lets you format your documents with the word wrap feature

36. Chapter Summary
Bytes are computer characters stored using numeric code, the numeric code is then formatted to plain English via ASCII, and the ASCII characters are stored in text files
The vi editor is a popular choice among UNIX users to edit text files
In the vi editor’s insert mode, characters you type are inserted in the file
With vi, you initially edit a copy of the file in the computer’s memory and the existing file itself is not altered until saved to disk

37. Chapter Summary
The Emacs editor is popular as an alternative to the vi editor and is included with UNIX systems, including Linux
Emacs has a powerful command syntax, is extensible, and supports a sophisticated language of macro commands
You start Emacs by typing the emacs command at the command line
You navigate an Emacs file by using cursor movement keys or Ctrl key combinations

38. Chapter Summary
In Emacs, you can undo your editing changes in sequence, even after you’ve made many changes
In Emacs, you insert text simply by typing it in, plus you have the editing features of copy, cut and paste, as well as text searching features