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

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 mark a region, first move the cursor to the beginning of the section and use [Ctrl- Spacebar] or and then move the cursor to the end of the section. You can use [Ctrl-x][Ctrl-x] to toggle between two ends.