Transcript Chapter Three - Mastering Editors

Chapter Three
The UNIX Editors
Lesson A
The vi Editor
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Objectives
• Describe an ASCII text file
• Explain why operating system editors use
ASCII files
• Create and edit simple documents using
the vi editor
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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
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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
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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
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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
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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
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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
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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
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Using the vi Editor
In insert mode,
every character
you type appears
on the screen.
You are actively
entering text into
the file.
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Using the vi Editor
To return to
command mode, hit
the Escape key.
Now, hit the . key to
repeat the last line.
The repeat command
repeats the last
insertion, or line.
Now, edit the new line
in order to create the
next item
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Using the vi Editor
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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
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Using the vi Editor
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Using the vi Editor
Use the delete
commands and
the cursor
movement keys
to edit the text
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Using the vi Editor
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Using the vi Editor
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Using the vi Editor
The status line at
the bottom of the
screen displays
information,
including lineoriented
commands and
error messages
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Using the vi Editor
During text
searches, you can
replace, too. Use
line-oriented
commands in ex
mode to perform
this action
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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, hit
Escape, type :w filename (write)
– While in command mode, use the :wq (write
and quit) command to save and exit vi, or the
:zz command to exit after saving
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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
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Using the vi Editor
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Using the vi Editor
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Lesson B
The Emacs Editor
Victoria College doesn’t have access to
an Emacs editor so just read through
the following section. You won’t have
any labs on Emacs
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Vi Practice
•
In the vi editor, show the command used to do the following:
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1.change to insert mode
–
•
2. change from insert mode to command mode
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<Escape>/unix <Enter>
Search for “unix” throughout the entire document and replace it with “linux”
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<Escape>O (uppercase O inserts a blank line above, lowercase o inserts a line below the cursor position)
6. search for the word “unix” in the current document
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<Escape>:wq OR
<CTRL>ZZ OR
<Escape>:x
5. add a blank line above the current cursor position
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x (You must be in command mode – if you are in insert mode, an x will be entered into the file.)
4. exit the editor and save changes in one step. Assuming that you have already associated a file
name with the file.
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–
–
•
Hit the escape key
3. delete a character
–
•
i
<Escape>:1,$s/unix/linux/g
7. exit the editor without saving changes
–
<Escape>:q!
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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
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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 email, for instance
• Emacs is reputed to have more features than
any other UNIX program
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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
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Using the Emacs Editor
The Emacs editor
opens in a GUI,
with menus
containing
command choices
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Using the Emacs Editor
Notice the
extensive
command choices
within the menu
structure
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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
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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
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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
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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
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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
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