Transcript Chapter 3
Chapter 3 Mastering Editors
Guide To UNIX Using Linux
Fourth Edition Chapter 3 (40 slides) CTEC 110 1
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 Chapter 3 (40 slides) CTEC 110 2
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 Chapter 3 (40 slides) CTEC 110 3
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 Chapter 3 (40 slides) CTEC 110 4
Look at Page 113 Chapter 3 (40 slides) CTEC 110 5
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 Chapter 3 (40 slides) CTEC 110 6
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 Chapter 3 (40 slides) CTEC 110 7
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 Chapter 3 (40 slides) CTEC 110 8
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 Blackboard for reference Chapter 3 (40 slides) CTEC 110 9
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 Chapter 3 (40 slides) CTEC 110 12
Moving the Cursor
• To move cursor use arrow keys (command/insert mode) or (in command mode) use: Chapter 3 (40 slides) CTEC 110 13
Deleting Text
• Deletion commands available (command mode) • dd is used for “cutting” text – Use “yank” (yy) command for “copying” text Chapter 3 (40 slides) CTEC 110 14
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 Chapter 3 (40 slides) CTEC 110 15
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: /\
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 Chapter 3 (40 slides) CTEC 110 19
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 Chapter 3 (40 slides) CTEC 110 20
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 23 Chapter 3 (40 slides) CTEC 110
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 Chapter 3 (40 slides) CTEC 110 25
Getting Help in vi
• • Use the help command – :help Other alternatives: – man vi ▫ From the command line – :!man vi ▫ From vi (command mode) Chapter 3 (40 slides) CTEC 110 26
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 Chapter 3 (40 slides) CTEC 110 27
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: Alt+f To save your work: – Use File menu – Use the save icon – Press Ctrl+x, Ctrl+s To exit: use menu, icon, or Ctrl+x, Ctrl+c Chapter 3 (40 slides) CTEC 110 31
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 Chapter 3 (40 slides) CTEC 110 32
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) Chapter 3 (40 slides) CTEC 110 33
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 Chapter 3 (40 slides) CTEC 110 34
Reformatting a File
• Alt+q turns on word wrap feature – Lines automatically wrap around from one line to the next Chapter 3 (40 slides) CTEC 110 35
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 Chapter 3 (40 slides) CTEC 110 36
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 Chapter 3 (40 slides) CTEC 110 37
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… Chapter 3 (40 slides) CTEC 110 40