Chapter 3 Mastering Editors

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Chapter 3Mastering Editors
Guide To UNIX Using Linux Fourth Edition
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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
• Used to create and edit documents
• Two text editors normally included in UNIX/Linux
  are screen editors
• 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
• Accessed by typing i
• Command mode
• Accessed by typing Esc
• Extended (ex) command set mode
• Accessed by typing in command mode
• Download the vi editor document on Canvas 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 /\lttop, /s..n, /passt, /!

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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 Ctrlz 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
• Example Altf
• To save your work
• Use File menu
• Use the save icon
• Press Ctrlx, Ctrls
• To exit use menu, icon, or Ctrlx, Ctrlc

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Deleting Information

• Del or Backspace keys delete individual
  characters
• Ctrlk deletes to the end of a line
• To undo a deletion, use Ctrlx, 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
  CtrlSpacebar
• Navigate to the end of the text you want to
  include
• Altw copies the text
• Ctrlw cuts the text
• To paste, move to where you want to place the
  text
• Ctrly (the yank command)

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Searching in Emacs

• One way to search in Emacs is to
• Press Ctrls
• Entering string to find (on status line)
• Pressing Ctrls repeatedly to find each
  occurrence
• Use Ctrlr 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

• Altq 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 Ctrlh and then type
  t
• To view general Emacs documentation
• Ctrlh (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