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GNU Emacs

Introduction​

GNU Emacs is a free implementation of Emacs, a family of text editors. It is an extensible, customizable and self-documenting real-time display editor. It provides a wide range of functionalities. For example, it can open multiple files, indent text, edit remote file, but can also act as a news/email client, display pdf, images, spawn a shell or maintain a calendar.

One philosophy behind GNU Emacs is to use a single program to answer all needs, making all features communicating between them with ease, implying a lighter desktop environment, and a common set of bindings to navigate between and inside each feature.

Another philosophy is to open Emacs a single time when booting its system and keep it open until the shutdown, in order to avoid the initial startup time.

It is possible to open the text-editor within the terminal with the command emacs -nw, -nw referring to \'no window\'.

Commands​

Emacs commands are invoked with either the Control key, symbolized as a capital C, or either the Meta key (Default is Alt), symbolized as a capital M.

All commands can be invoked using their name, by using M-x followed by the function name.

It is possible to display all commands using M-x describe-bindings

Here are some the basic navigation commands, some resources in the next sections should help you learn more about them.

  • C-f : Move right (forward)
  • C-b : Move left (backward)
  • C-p : Move up (previous)
  • C-n : Move down (next)
  • C-x C-c: Close Emacs
  • C-x C-f : Open a file
  • C-x C-s : Save file
  • C-x 2 : Split window horizontally
  • C-x 3 : Split window vertically
  • C-x o : Focus another windows
  • C-x 0 : Close focused window

Help​

One of the greatest functionality of Emacs is the huge documentation that comes with it. It is possible to display help for each functions or keybinding using a simple command.

By using C-h C-h it is possible to see all help commands available. Using C-h followed by the key associed with the category invoke its help functionality.

The two major help commands are the following:

  • A tutorial explaining keybindings can be invoked using M-x help-with-tutorial or shortly C-h t. The keybindings are the same as most terminals.
  • The Emacs Manual can be opened using M-x info-emacs-manual or C-h r.

Other great help features exist, for example C-h f offers the possibility to enter the name of a command to read a short documentation about it.

Default features​

Emacs provides several useful features by default, we can mention some of them:

man​

You can read man page within emacs using M-x man, it will search by default the word under the cursor.

dired​

When opening a directory, a special mode called dired is used to perform actions on files. The most used bindings are the following:

  • e : Open file in edit mode
  • v : Open file in visual mode (read only)
  • d : Mark a file for deletion
  • u : Unmark a file
  • x : Execute the deletion
  • C : Copy file
  • R : Rename the file
  • M : Change permissions
  • G : Change group
  • S : Create a symlink
  • q : Quit buffer

org​

A whole framework aimed to improve organization in plaintext, named org, is integrated in GNU Emacs. It is a plain text markup language having as advantage to be rendered directly into Emacs, having special bindings to improve note taking and working in symbiosis with other org features.

For example, it is possible to annotate sections of text with specials tags (Timedate, TODO, AUTHORS, ...), to include link to local files, or even to indicate sections of code, evaluate them and add results into the file.

Basic configuration​

Emacs Lisp​

GNU Emacs is extremely powerful and easy regarding configurations. All its configuration is possible using Emacs Lisp, a flavor of Lisp language. Configurations are located within the ~/.emacs file.

To change bindings, use the function global-set-key:

;; Set the binding "C-c h" for the function 'replace-string'
(global-set-key (kbd "C-c h") 'replace-string)

To change configuration value, use the function setq:

;; Set offset to 4 in c file
(setq c-basic-offset 4)

It is also possible to apply a configuration only in certain circumstances, by calling a function only when a mode is activated.

;; Set the python indentation to 2, when opening a python file
(add-hook 'python-mode-hook (lambda () (setq python-indent-offset 2)))

Visual configuration​

Emacs also provides a visual and easy mode to help customize the editor. To use it, just invoke M-x customize.

To customize the text, you can invoke M-x list-faces. It will show a list of all faces used by Emacs, referring to all displayed text under all circumstances. You can find the name of the face used by a text by invoking M-x describe-text-properties having the cursor on the targeted text.

External packages​

It is possible to add custom packages by using Emacs packages manager, for example MELPA. Listing and installing packages are possible using the command M-x list-packages.

Some of them are well known and could be useful, here is a short list:

  • Magit : Providing a git client inside Emacs
  • evil : Layer to use vim bindings
  • Treemacs : Adding a tree layout file explorer

Configuration framework​

Configuration frameworks are set of configuration files added to Emacs to provides a choice of external packages already configured.

The most popular ones are the following:

  • Doom emacs
  • Spacemacs

Here is some useful links to go further: