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Emacs

This page is a beginner's tutorial for Emacs.

15-minute introduction to Emacs.

Introduction

Emacs is an editor that is very easy to get started with; it can be used with just a few lines of configuration. However, becoming proficient in using Emacs for various tasks requires some time.

As an introductory tutorial, this page only covers the basic functionalities of Emacs and convenient methods for writing and debugging code with Emacs.

Getting Started

Commands

Commands play a significant role in Emacs.

Press the Application key1 (on Windows systems, Emacs does not assign this key by default; it needs to be set manually) or use the shortcut M-x (Alt+x) to open the command input. After typing the command, press Enter to execute it.

Typically, the es or eshell command is used to open Eshell (similar to a terminal).

Inputting commands can often be replaced by shortcuts.

Buffers

A buffer refers to an opened file or process. Modifications made in the buffer do not affect the file until saved.

Click the buffer name at the bottom of the buffer area or use shortcuts to switch between buffers.

Compiling, Debugging, and Running

The entries for compiling and debugging functions are in the Tools dropdown menu in the top menu bar. Users can also use commands or customize shortcuts for compiling and debugging.

Programs can be run using a terminal or Eshell.

After selecting Debug (gud-gdb) in Tools, enter the program name (usually filled in automatically, but if the program was saved under a different name during the process or if two programs need debugging, the automatically filled filename may be incorrect) to start debugging.

Splitting Windows

This feature allows users to view the contents of multiple buffers simultaneously without switching back and forth, making it convenient for testing and debugging code.

The split-window feature can display multiple windows at once. Dragging the edges of a window with the mouse can resize the window.

Several shortcuts:

  • Delete split window "C-x 0": Remove this split window.
  • Split window horizontally "C-x 3": Split this window horizontally into two halves.
  • Split window vertically "C-x 2": Split this window vertically into two halves.

A recommended window layout is to divide the window into four parts: first, split horizontally, adjusting one part to about ¾ of the screen width as the editing window. Then, split the other part horizontally; one part serves as the window for displaying debugging and compilation information, and the other part is split vertically, with one side opening the input file and the other opening the output file.

Shortcuts

Emacs has an extremely rich set of shortcuts, which can greatly improve work efficiency. Users can customize shortcuts or set shortcut mappings in the configuration.

Due to the large number of shortcuts, using Emacs shortcuts differs from using operating system shortcuts.

For convenience, the following conventions are made:

Character Key
C Ctrl
M Alt
? Any key

Generally, there are three types:

  • F?, ESC: Press the corresponding function key directly.
  • M-?, C-?, C-M-?: Press Alt or Ctrl while pressing ?.
  • ? ?: Press the key represented by the first ?, release it, then press the key represented by the second ?.

Here are some commonly used shortcuts:

  • C-x h: Select all
  • C-x left, C-x right: Switch to the previous/next buffer
  • C-x d: Open a directory
  • C-x C-f: Open a file (if the file does not exist, create a new file)

Personalization

The default installation of Emacs has an unattractive appearance and is not very user-friendly, so personalization settings are needed.

Since configurations are hard to remember, it is recommended not to memorize configurations for parts that can be set directly.

Direct Settings

  • Options: Highlight Matching Parentheses Highlight matching parentheses
  • Options: Blink Cursor Set cursor blinking
  • Options Show/Hide: Tool Bar Show/hide toolbar (default is show, recommended to hide)
  • Options: Use CUA Keys After checking, you can use Ctrl + C, Ctrl + V, etc., for copy-paste shortcuts
  • Options Customize-Emacs: Custom Theme Choose a color scheme, then click Save after selection
  • Options: Save Options Save configuration

Configuration

Show hidden files in the home directory (on Windows systems, in the AppData\Roaming directory under the user directory). ".emacs" is the configuration file (if it doesn't exist, it means it hasn't been saved before). Open and modify it. If Emacs is already open, you need to restart Emacs for the configuration to take effect.

The following configuration is recommended for exam environments.

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;; Set one-key compilation. You can add parameters yourself. Not recommended for exam environments; do not rely on one-key compilation.
(defun compile-file ()(interactive)(compile (format "g++ -o %s %s -g -lm -Wall" (file-name-sans-extension (buffer-name))(buffer-name))))
(global-set-key [f9] 'compile-file)
;;;; Set compilation shortcut (do not conflict with one-key compilation if set)
;;(global-set-key [f9] 'compile)

(global-set-key (kbd "C-a") 'mark-whole-buffer) ;; Select all shortcut
(global-set-key (kbd "C-z") 'undo) ;; Undo shortcut
(global-set-key [f10] 'gud-gdb) ;; GDB debugging shortcut
(global-set-key (kbd "RET") 'newline-and-indent) ;; Newline with auto-indent
(global-set-key (kbd "C-s") 'save-buffer) ;; Set save shortcut
(setq-default kill-ring-max 65535) ;; Increase undo history size

;; C++ code style, generally controls indentation rules
;;;"bsd" All braces on new lines
;;;"java" All braces on the same line. else follows the closing brace
;;;"awk" Only braces for namespaces, class definitions, and function definitions are on new lines. else follows the closing brace
;;;"linux" Only braces for namespaces, class definitions, and function definitions are on new lines. else follows the closing brace. Generally, this style uses 8-space indentation
(setq-default c-default-style "awk")

Full Configuration 
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;; Set one-key compilation
(defun compile-file ()(interactive)(compile (format "g++ -o %s %s -g -lm -Wall" (file-name-sans-extension (buffer-name))(buffer-name))))
(global-set-key [f9] 'compile-file)
;;;; Set compilation shortcut (do not conflict with one-key compilation if set)
;;(global-set-key [f9] 'compile)

;; Essential for exam environments
(global-set-key (kbd "C-a") 'mark-whole-buffer) ;; Select all shortcut
(global-set-key (kbd "C-z") 'undo) ;; Undo shortcut
(global-set-key [f10] 'gud-gdb) ;; GDB debugging shortcut
(global-set-key (kbd "RET") 'newline-and-indent) ;; Newline with auto-indent
(global-set-key (kbd "C-s") 'save-buffer) ;; Set save shortcut
(setq-default kill-ring-max 65535) ;; Increase undo history size
;;(define-key key-translation-map [apps] (kbd "M-x")) ;; Set command shortcut on Windows systems

;; Set indentation
;;; C++ code indentation length.
(setq-default c-basic-offset 4)
;;; Use tab for indentation
(setq-default indent-tabs-mode t)
;;; Tab length. Must match indentation length.
(setq-default default-tab-width 4)
(setq-default tab-width 4)

;; Set default encoding environment
(set-language-environment "UTF-8")
(set-default-coding-systems 'utf-8)

;; Do not show welcome screen
(setq-default inhibit-startup-screen t)

;; Set title
(setq-default frame-title-format "")

;; Display line numbers
(global-display-line-numbers-mode t)

;; Highlighting
(global-hl-line-mode 1);; Highlight current line
(show-paren-mode t);; Highlight matching parentheses
(global-font-lock-mode t);; Syntax highlighting

;; Allow pasting between Emacs and external programs (seems allowed by default)
(setq-default x-select-enable-clipboard t)

;; Set font to Ubuntu Mono size 16. If the font does not exist, an error will occur.
(set-face-attribute 'default nil :font "Ubuntu Mono-16")
;(set-face-attribute 'default nil :font "Consolas-16") ;; Use this line for Windows systems

;; Mouse wheel support
(mouse-wheel-mode t)

;; Set cursor shape to vertical line (default is block)
(setq-default cursor-type 'bar)

;; Change yes/no prompts to y/n
(fset 'yes-or-no-p 'y-or-n-p)

;; Transparency
(set-frame-parameter (selected-frame) 'alpha (list 85 60))
(add-to-list 'default-frame-alist (cons 'alpha (list 85 60)))

;; Reduce the number of lines scrolled per page to prevent full-page scrolling
(setq-default scroll-margin 3 scroll-conservatively 10000)

;; Optimize file tree structure
(ido-mode t)

;; Color scheme
(setq default-frame-alist
         '((vertical-scroll-bars)
           (top . 25)
           (left . 45)
           (width . 120)
           (height . 40)
           (background-color . "grey15")
           (foreground-color . "grey")
           (cursor-color . "gold1")
           (mouse-color . "gold1")
           (tool-bar-lines . 0)
           (menu-bar-lines . 1)
           (scroll-bar-lines . 0)
           (right-fringe)
           (left-fringe)))

(set-face-background 'highlight "gray5")
(set-face-foreground 'region "cyan")
(set-face-background 'region "blue")
(set-face-foreground 'secondary-selection "skyblue")
(set-face-background 'secondary-selection "darkblue")
(set-cursor-color "wheat")
(set-mouse-color "wheat")

(custom-set-variables
 '(ansi-color-faces-vector
   [default default default italic underline success warning error])
;; Enable Ctrl-x Ctrl-c Ctrl-v = cut copy paste
 '(cua-mode t nil (cua-base))
 '(show-paren-mode t)
;; Hide toolbar
 '(tool-bar-mode nil))
;; Disable cursor blinking
 '(blink-cursor-mode nil)
(custom-set-faces)

Further Reading

To start Emacs in terminal mode, add the -nw parameter at startup. Emacs has various variants, such as GCC Emacs which uses native-comp to reduce latency and its pure GTK version variant, and Emacs Macport optimized for macOS.

Emacs has a centralized software repository. After configuration, plugins can be installed via M-x package-install. Using a mirror site can speed up downloads.

Emacs can use a Language Server Protocol (LSP) to improve the editing experience. Currently, the recommended C++ backend is Clangd. The frontend can use Eglot or Emacs LSP. Refer to this entry for help in choosing a frontend.

Org Mode documents with the extension .org can be converted to Markdown documents using Pandoc.

References and Notes

  1. This key is used to bring up the right-click menu, usually the first key to the left of the right Ctrl. ↩

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