CS 497C – Introduction to UNIX Lecture 17: - The GNU emacs Editor

1. CS 497C – Introduction to UNIXLecture 17: - The GNU emacs Editor Chin-Chih Changchang@cs.twsu.edu

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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].

8. 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

9. 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].

10. 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].

11. 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.

12. 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.