Chapter 3
Mastering Editors
Guide To UNIX Using Linux
Fourth Edition
Chapter 3 (40 slides)
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Objectives
• Explain the basics of UNIX/Linux files,
including ASCII, binary, and executable
files
• Understand the types of editors
• Create and edit files using the vi editor
• Create and edit files using the Emacs
editor
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Understanding UNIX/Linux Files
• Almost everything you create in
UNIX/Linux is stored in a file
• Bit: binary digit
– In one of two states: 0 or 1
• Machine language: exclusive use of
0s and 1s as a way to communicate
with computer
– Used by earliest programmers
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ASCII Text Files
•
•
•
•
Byte (binary term): string of eight bits
A byte can be configured into fixed patterns of bits
– ASCII: American Standard Code for Information
Interchange
▫ 256 different characters
– Unicode
▫ Supports up to 65,536 characters
Text files: contain nothing but printable characters
Binary files: contain nonprintable characters
– Example: machine instructions
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Look at Page 113
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Binary Files
• Some things cannot be represented
with ASCII codes
• Binary files are used instead
– Example: graphic files include bit
patterns
▫ Bitmap: made of rows and columns of dots
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Executable Program Files
• Text files containing program code
are compiled into machine-readable
language
• Scripts are files containing commands
– Typically interpreted, not compiled
• Executables: compiled and
interpreted files that can be run
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Using Editors
•
•
Editor: program for creating and modifying
files containing source code, text, data,
memos, etc.
Text editor: a simplified word-processing
program
–
•
Two text editors normally included in
UNIX/Linux are screen editors
–
–
•
Used to create and edit documents
vi
Emacs
Line editor: works with one line (or group of
lines) at a time
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Using the vi Editor
• vi is a visual editor
• vi is also a modal editor
– Supports three modes
▫
Insert mode
›
▫
Command mode
›
▫
Accessed by typing “i”
Accessed by typing Esc
Extended (ex) command set mode
›
Accessed by typing “:” in command mode
• Download the vi editor document on
Blackboard for reference
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Creating a New File in the vi Editor
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Inserting Text
• When you start vi, you are in
command mode
• To insert text in your file, switch to
insert mode
– Use i (insert) command
• To return to command mode, press
Esc
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Repeating a Change
• Use a period (.) to repeat the most
recent change you made
– Repeat command
– Works in command mode
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Moving the Cursor
•
To move cursor use arrow keys (command/insert mode)
or (in command mode) use:
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Deleting Text
•
Deletion commands available (command mode)
•
dd is used for “cutting” text
–
Use “yank” (yy) command for “copying” text
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Undoing a Command
• Type u to use the undo command
• Example:
– If you delete a few lines from a file by
mistake, type u to restore the text
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Searching for a Pattern
• To search forward for a pattern of characters:
– Type a forward slash (/)
– Type the pattern you are seeking
– Press Enter
• Examples: /\<top, /s..n, /pas[st], /!$
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Searching and Replacing
•
•
Screen-oriented commands execute at the
location of the cursor
Line-oriented commands require you to
specify an exact location (an address) for the
operation
–
–
–
Preceded by a colon (:)
Operate in ex mode
Used for commands that perform more than one
action
▫
Example: searching and replacing
:1,$s/insure/ensure/g
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Saving a File and Exiting vi
•
•
To save file without exiting, use :w
To save and exit, use :wq, :x, ZZ
(Do this in command mode)
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Adding Text from Another File
• To copy entire contents of one file
into another file:
– Use vi to edit the file you would like to
copy into
– Use the command :r filename
▫ filename is the name of the file that
contains the information you want to copy
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Leaving vi Temporarily
• To launch a shell or execute other
commands from within vi, use :!
– Example:
▫ :!cal
• To run several command-line
commands in a different shell without
closing vi session
– Use Ctrl+z to display the command line
– Type fg to go back to vi
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Leaving vi Temporarily (continued)
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Changing Your Display
While Editing
• To turn on line numbering
:set number
• To delete lines 4 through 6 (ex mode)
:4,6d
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Copying or Cutting and Pasting
• The command yy copies (yanks) a
specified number of lines
– To cut the lines, use dd
– Lines are placed in clipboard
• Use p to paste the clipboard contents
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Printing Text Files
• To print a file, use the lpr (line print)
shell command
– Example:
:!lpr -P lp2 accounts
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Canceling an Editing Session
• Canceling an editing session will
discard all the changes you have
made
• Or, save changes you made since last
using :w
– Saves file without exiting vi
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Getting Help in vi
• Use the help command
– :help
• Other alternatives:
– man vi
▫ From the command line
– :!man vi
▫ From vi (command mode)
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Using the Emacs Editor
•
Emacs is a popular UNIX/Linux text editor
–
–
–
–
Not modal
More complex than vi
More consistent than vi
Sophisticated macro language
▫
▫
–
–
Macro: set of commands that automates a complex
task
Uses: read mail, edit contents of directories, etc.
Powerful command syntax
Extensible
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Using the Emacs Editor (continued)
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Using the Emacs Editor (continued)
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Creating a New File in Emacs
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Navigating in Emacs
•
•
To create a new file: emacs filename
To navigate in the file, use the cursor
movement keys or Ctrl/Alt key combinations
–
•
To save your work:
–
–
–
•
Example: Alt+f
Use File menu
Use the save icon
Press Ctrl+x, Ctrl+s
To exit: use menu, icon, or Ctrl+x, Ctrl+c
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Deleting Information
• Del or Backspace keys delete
individual characters
• Ctrl+k deletes to the end of a line
• To undo a deletion, use Ctrl+x, u
– Repeatedly undoes each deletion
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Copying, Cutting, and Pasting Text
• To Copy-Paste or Cut-Paste:
– Mark the text
▫
▫
Position cursor at the beginning, and
Ctrl+Spacebar
Navigate to the end of the text you want to
include:
›
›
Alt+w copies the text
Ctrl+w cuts the text
– To paste, move to where you want to place
the text
▫
Ctrl+y (the yank command)
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Searching in Emacs
• One way to search in Emacs is to:
– Press Ctrl+s
– Entering string to find (on status line)
– Pressing Ctrl+s repeatedly to find each
occurrence
• Use Ctrl+r to search backward
• Other alternatives:
– Use search forward for a string icon
– On the menu: Edit  Search  Search
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Reformatting a File
• Alt+q turns on word wrap feature
– Lines automatically wrap around from
one line to the next
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Getting Help in Emacs
• Emacs comes with extensive
documentation and a tutorial
– Tutorial is useful for getting up to speed
quickly
▫ Click Help menu  Emacs Tutorial
▫ Or (in most versions), type Ctrl+h and
then type t
– To view general Emacs documentation:
▫ Ctrl+h (press one or two times)
▫ Or, man emacs at command line
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Summary
•
•
Bytes: computer characters (a series of bits)
stored using numeric codes
The vi editor is popular among UNIX/Linux users
–
–
Three modes: insert (i), command (Esc), and ex (Esc :)
With vi, you edit a copy of the file placed in memory
▫
•
File is not altered until you save it on disk
Emacs is a popular alternative to vi
–
–
–
Supports powerful command syntax and is extensible
Insert text simply by typing
Sophisticated macro language
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Command Summary
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Command Summary (continued)
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Chapter 3 Unix Exercises
• Work through Hands-on Projects
at end of chapter 3
• Canvas: Review Questions
– (Do not do questions 22,23,24 and 25)
• Read chapter 4 before next class session
• Quiz 3 Unix…
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