Emacs

A short introduction to emacs given as part of the tech talk series.

"Emacs outshines all other editing software in approximately the same way that the noonday sun does the stars. It is not just bigger and brighter; it simply makes everything else vanish." -Neal Stephenson, "In the Beginning was the Command Line"

"Show me your ~/.emacs and I will tell you who you are." - Bogdan Maryniuk

"Emacs is like a laser guided missile. It only has to be slightly mis-configured to ruin your whole day." -Sean McGrathi

"While any text editor can save your files, only Emacs can save your soul." -Per Abrahamseni

The home page of GNU Emacs is here, which also takes you to the download area. A good book describing emacs is Mastering Emacs. A number of tutorials are found at ErgoEmacs. Please also have a look at the EmacsWiki for a lot of useful information. Finally, Sacha Chua usually has a lot of interesting news about emacs on her blog. Wikipedia has a compilation of differences between emacs and vim on their page Editor war.

Configuration

The configuration of emacs is usually in $HOME/.emacs or $HOME/.emacs.d/init.el. Here are a couple of things which I use personally:

• Make emacs start up without menu bar, tool bar or scroll bar:

(setq inhibit-startup-message t)
(tool-bar-mode -1)
(menu-bar-mode -1)
(scroll-bar-mode -1)
;; turn transient mark mode on
(transient-mark-mode 1)
;; define my location for emacs calendar
(setq-default european-calendar-style t)
(setq calendar-latitude 57.4)
(setq calendar-longitude 11.9)
(setq calendar-location-name "Onsala, SE")

• Customize modes:

(defun my-c-mode-hook ()
  (setq c-basic-offset 4)
  (setq indent-tabs-mode nil)
  (c-set-offset 'case-label 2)
  (c-set-offset 'statement-case-intro 2)
  )
(add-hook 'c-mode-hook 'my-c-mode-hook)
(add-hook 'c++-mode-hook 'my-c-mode-hook)
(add-hook 'tex-mode-hook #'(lambda () (setq ispell-parser 'tex)))

• Define your own functions:

(defun insert-datetime (arg)
  "Without argument: insert date as yyyy-mm-dd
With C-u: insert time
With C-u C-u: insert date and time"
  (interactive "P")
  (cond ((equal arg '(4)) (insert (format-time-string "%T")))
    ((equal arg '(16)) (insert (format-time-string "%Y-%m-%d %T")))
    (t (insert (format-time-string "%Y-%m-%d")))))

• Use emacs built-in customization

M-x customize

Packages

• Configure package repository:

(require 'package)
(setq package-enable-at-startup nil)
(add-to-list 'package-archives
       '("melpa" . "https://melpa.org/packages/"))
(package-initialize)
 (unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package))
;; example: package magit
(use-package magit
  :config
  (global-set-key (kbd "C-x g") 'magit-status))

• Install additional packages:

M-x package-refresh-contents
M-x packagae-install<TAB>

Windows

• I.e. what emacs means by that ;)

C-x 2 split vertically
C-x 3 split horizontally
C-x o goto next window
C-x 1 keep only current window
C-x 0 kill current window
C-x C-b show list of buffers
C-x b switch buffer
C-x d enter dired mode

Search and replace

• Incremental search

C-s isearch-forward
C-r isearch-backward
C-w yank (i.e. paste) word at point onto end of search string

• Query and replace (note emacs is case insensitive by default!)

M-% query-replace           ;; will prompt for from-string and to-string
C-M-% query-replace-regexp  ;; same for regualr expressions

Macros

• Define and execute macros, use counters which self-increment on each execution

C-x (        ;; start macro definition
C-x )        ;; end macro definition
C-x e        ;; execute macro
e            ;; execute again
C-x C-k C-c  ;; set counter
C-x C-k C-i  ;; insert counter (or use F3)
C-x C-k C-a  ;; add to counter

Rectangle mode

• Work with rectangular text areas, defined by the beginning of the region and current cursor position (what emacs calls "point"). Note, that highlighting will typically extend beyond the rectangle.

;; mark region which will define a rectangle
C-x r t      ;; will prompt for string to replace rectangle
C-x r k      ;; kill rectangle
C-x r y      ;; yank (i.e. paste) rectangle

Help

• Get help on mode, variables and key shortcuts

M-x describe-mode
M-x describe-variable
M-x describe-key

Franz's configuration

• To enable tabbar mode you need to install emacs-goodies-el via apt-get or the like. One way to set it up is described here.

• The description of how to get Python syntax checking to work in emacs is here.

• And here is a manual on how to install jedi in emacs, provides code auto completion and on-the-fly help.

• One more thing I forgot to add: By default emacs does not scroll smoothly but in steps of xx-lines -- I hate it. To have smooth scrolling starting when you're 5 lines away from the bottom/top of the page add the following to your configuration (requires package smooth-scroling):

(require 'smooth-scrolling)
(smooth-scrolling-mode 1)
(setq smooth-scroll-margin 5)