CS 497C

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CS 497C Introduction to UNIXLecture 17 - The
GNU emacs Editor

• Chin-Chih Changchang_at_cs.twsu.edu

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The GNU emacs Editor

• emacs was create by Richard Stallman (the founder
  of GNU, now the Free Software Foundation).
• The program was originally written as a set of
  macros for the TECO editor.
• emacs is not available in all UNIX systems but is
  standard on Linux.
• GNU emacs is more than an editor it handles a
  number of non-editing functions.

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The GNU emacs Editor

• vi often does things with fewer keystrokes, but
  emacs easily surpass vi when it comes to
  searching and replacing and using macros.
• After invoking emacs, you have a full screen. 22
  of the 25 lines are available for editing.

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The GNU emacs Editor

• The top one in reverse video shows a menu, the
  lower one in reverse video shows the mode line,
  and the bottom line is the minibuffer showing an
  emacs-generated message.
• In the mode line you can see the filename and the
  cursor position (L1).
• Like most word processors unlike vi, emacs is a
  mode-less editor.

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emacs Preliminaries

• In the emacs documentation, key sequences
  described as
• C-e This is Ctrl-e.
• C-x C-b This is Ctrl-xCtrl-b.
• C-x b This is Ctrl-xb.
• M-e This is Meta-e.
• On the PC, you can use the Alt key or
  Esc-release to substitute Meta key.

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emacs Preliminaries

• When you press a valid key sequence, emacs
  executes a command associated with the key.
• For instance, when you press Ctrl-n, emacs
  executes the next-line command.
• To canceling a sequence, use Ctrl-g.
• emacs reads the file .emacs at startup. emacs q
  ignores the .emacs file at startup.
• Use Ctrl-xCtrl-c to quit emacs.

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Inserting and Replacing Text

• The default input mode is the insert mode. To
  switch to the overwrite mode, press the Insert
  key or enter the overwrite-mode command which can
  be done by the key sequence Alt-xovtab.
• To enter a control character, first enter
  Ctrl-q and then the control character.
• To save a file, use Ctrl-x Ctrl-s.
• To save a file as a different filename, use
  Ctrl-xCtrl-w.

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Saving Text

• To open a different file, use Ctrl-xCtrl-f.
• emacs has an autosave feature which automatically
  saves a copy of the buffer in filename.
• To recover from the crash, use the recover-file
  command
• Alt-xrecover-file

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The Digital Argument

• To perform a command as many times, use the
  digital argument. The number is prefixed by the
  Meta (Alt on PC) key.
• For example, to delete 5 characters, use
  Meta-5Ctrl-d.
• The other way is to use the universal argument
  Ctrl-u such as
• Ctrl-u5Ctrl-d.

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Navigation

• emacs uses the control keys to move in the four
  directions. These keys are quite intuitive b
  (back), f (forward), p (previous line) and n
  (next line).
• Ctrl-b move left, Ctrl-f move right,
  Ctrl-p move up, Ctrl-n move down.
• To scroll full page forward, use Ctrl-v. To
  scroll full page backward, use Alt-v.
• To redraw the screen and position cursor at
  center of screen, use Ctrl-l.

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Navigation

• To move to the beginning of a line, use Ctrl-a.
  To move the end of a line, use Ctrl-e.
• To move the beginning of the word, use Alt-f.
  To move the end of the word, use Alt-b.
• To move the specified line number, use Alt-x
  goto-line Enter and then type the line number.

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Working with Regions

• To move to the beginning of the file, use
  Alt-lt. To move to the end of the file, use
  Alt-gt.
• To mark a region, first move the cursor to the
  beginning of the section and use Ctrl-Spacebar
  or Ctrl-_at_ and then move the cursor to the end
  of the section.
• You can use Ctrl-xCtrl-x to toggle between
  two ends.