Introduction%20to%20Unix%20(CA263)%20%20File%20Editing

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Introduction to Unix (CA263) File Editing

• By
• Tariq Ibn Aziz

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Objectives

• After reading this chapter, you should be able
  to
• 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

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The Unix Language

• ASCII, American Standard Code for Information
  Interchange
• Originally, ASCII used only 7 bits (0 and 1)
  providing 128 characters
• Extended ASCII uses 8 bits to store 256
  characters. For example English letter H has a
  decimal code 72. In term of bits, H is 01001000

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ASCII Text Files

• Computer files containing nothing but printable
  characters are called text file.
• Files containing nonprintable characters, such as
  machine instructions, are called binary files.
• Unicode offers up to 65,536 characters.
• Unicode was developed because 256 character in
  ASCII are not enough to support some languages,
  such as Chinese, that need more than 256
  characters.

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ASCII Text File
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USING THE VI EDITOR

• The vi editor is a modal editor.
• It works in three mode
• Insert mode
• lets you enter text, is accessed by typing the
  letter i
• Command mode
• Which is started by pressing Esc
• Ex mode
• Employs an extended set of commands that were
  initially used in an early UNIX editor called ex.
• Press Esc and type () to enter extended command

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USING THE VI EDITOR

• Start the vi editor with the e option (vi e
  filename), which places vi exclusively in ex
  mode.
• To use the vi editor, it is important to master
  the following tasks
• Creating a file
• Inserting, editing, and deleting text
• Searching and replacing text
• Adding text from other files
• Copying, cutting, and pasting text
• Printing a file
• Saving a file
• Exiting a file

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Creating a New File in the vi Editor

1. Enter vi plus the name of the file you want to
   create, such as vi data.
2. Press Esc, type w

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Creating a New File in the vi Editor

• Another Way to create a file
• open the vi editor without specifying the file
  name with the vi command
• You can save the file and specify a file name at
  any time by pressing Esc, typing w filename

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Using the vi Editor (continued)
To create a new file in the vi editor, type vi
and the name of the new file at the command prompt
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Inserting Text

• Before you can insert text in your new file, you
  must use the i (insert) command.
• In insert mode, every character you type appears
  on the screen.
• You can return to command mode at any time by
  pressing the Esc key.

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Repeating a Change

• When started, the vi editor is in command mode
• To insert text into a file, you must switch to
  insert mode
• You can repeat the line just entered with the
  repeat command (.)
• Note You must press Esc to use (.) to repeat the
  command

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Moving the Cursor

• Designers of vi chose the letter keys because of
  their relative position on the keyboard.

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Deleting Text

• 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

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Searching and Replacing Text

1. Searching and replacing is a line-oriented
   command that executes independently of the cursor
   position
2. To find more instances, type n while you are in
   command mode

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Save File and Exit

• 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 iv, or the zz
  command to exit after saving
• You can also use x to save and exit

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Save File and Without Exiting
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Information about file status

• If you are in an editing session and want to
  review information about the file status, press
  Ctrlg or CtrlG
• The status line at the bottom of the screen
  displays information, including line-oriented
  commands and error messages.

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Adding Text from Another File

• To copy the entire contents of one file into
  another file
• (1) use the vi editor to edit the file you want
  to copy into and
• (2) use the command r filename, where filename
  is the name of the file that contains the
  information you want to copy

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Leaving vi Temporarily

• If you want to execute other UNIX/Linux commands
  while you work with vi, you can launch a shell or
  execute other commands from within vi.
• Go to command mode
• Type !cal (a colon, an exclamation point, and
  the command)
• press Enter.

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Using the vi Editor (continued)

1. Turn on line numbering when you want to work with
   a range of lines and refer to the line numbers to
   specify text
2. To turn on line numbering, use the set number
   command

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Copying or Cutting and Pasting

• You can use the yy command in vi to copy a
  specified number of lines
• To cut the lines from the file and store them on
  the clipboard, use the dd command.

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Printing Text Files

• Sometimes you want to print a file before you
  exit the vi editor.
• Type !lpr and then type the name of the file you
  want to print.
• You might have two printers, lp1 and lp2.To print
  the file accounts to lp2, enter !lpr -P lp2
  accounts and press Enter.

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Canceling an Editing Session

• You might have to cancel editing session.
• To cancel session, enter q! and press Enter.

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Getting Help in vi

• While you are in vi, press Esc, type !man vi,
  and press Enter
• Type q and press Enter to go back into your
  editing session.

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Chapter Summary

• Bytes are computer characters stored using
  numeric code (e.g., ASCII)
• The vi editor is a popular choice among
  UNIX/Linux users to edit text files