CS 497C - Introduction to UNIX
Lecture 17: - The GNU emacs Editor
Chin-Chih Chang chang@cs.twsu.edu

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.

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.
 
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.

emacs Preliminaries
* In the emacs documentation, key sequences described as:
 - C-e - This is [Ctrl-e].
 - C-x C-b - This is [Ctrl-x][Ctrl-b].
 - C-x b - This is [Ctrl-x]b.
 - M-e - This is [Meta-e].
* On the PC, you can use the [Alt] key or [Esc]-release to substitute 
  [Meta] key.

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-x][Ctrl-c] to quit emacs.

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-x]ov[tab].
* 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-x][Ctrl-w].

Saving Text
* To open a different file, use [Ctrl-x][Ctrl-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-x]recover-file

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-5][Ctrl-d]. 
* The other way is to use the universal argument - [Ctrl-u] such as 
  [Ctrl-u]5[Ctrl-d].

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].

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.

Working with Regions
* To move to the beginning of the file, use [Alt-<]. To move to the end 
  of the file, use [Alt->].
* To mark a region, first move the cursor to the beginning of the 
  section and use [Ctrl-Spacebar] or [Ctrl-@] and then move the cursor 
  to the end of the section.
* You can use [Ctrl-x][Ctrl-x] to toggle between two ends.