I was surprised not to find an introduction to Emacs Lisp on https://learnxinyminutes.com so I created one. This page is now on https://learnxinyminutes.com/docs/elisp/ too.

Comments and feedback are welcome !

;; This gives an introduction to Emacs Lisp in 15 minutes (v0.2d) ;; ;; Author: Bastien / @bzg2 / https://bzg.fr ;; ;; First make sure you read this text by Peter Norvig: ;; http://norvig.com/21-days.html ;; ;; Then install GNU Emacs 24.3: ;; ;; Debian: apt-get install emacs (or see your distro instructions) ;; MacOSX: http://emacsformacosx.com/emacs-builds/Emacs-24.3-universal-10.6.8.dmg ;; Windows: http://ftp.gnu.org/gnu/windows/emacs/emacs-24.3-bin-i386.zip ;; ;; More general information can be found at: ;; http://www.gnu.org/software/emacs/#Obtaining ;; Important warning: ;; ;; Going through this tutorial won't damage your computer unless ;; you get so angry that you throw it on the floor. In that case, ;; I hereby decline any responsability. Have fun! ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ;; Fire up Emacs. ;; ;; Hit the `q' key to dismiss the welcome message. ;; ;; Now look at the gray line at the bottom of the window: ;; ;; "*scratch*" is the name of the editing space you are now in. ;; This editing space is called a "buffer". ;; ;; The scratch buffer is the default buffer when opening Emacs. ;; You are never editing files: you are editing buffers that you ;; can save to a file. ;; ;; "Lisp interaction" refers to a set of commands available here. ;; ;; Emacs has a built-in set of commands available in every buffer, ;; and several subsets of commands available when you activate a ;; specific mode. Here we use the `lisp-interaction-mode', which ;; comes with commands to evaluate and navigate within Elisp code. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ;; Semi-colons start comments anywhere on a line. ;; ;; Elisp programs are made of symbolic expressions ("sexps"): (+ 2 2) ;; This symbolic expression reads as "Add 2 to 2". ;; Sexps are enclosed into parentheses, possibly nested: (+ 2 (+ 1 1)) ;; A symbolic expression contains atoms or other symbolic ;; expressions. In the above examples, 1 and 2 are atoms, ;; (+ 2 (+ 1 1)) and (+ 1 1) are symbolic expressions. ;; From `lisp-interaction-mode' you can evaluate sexps. ;; Put the cursor right after the closing parenthesis then ;; hold down the control and hit the j keys ("C-j" for short). (+ 3 (+ 1 2)) ;; ^ cursor here ;; `C-j' => 6 ;; `C-j' inserts the result of the evaluation in the buffer. ;; `C-x C-e' displays the same result in Emacs bottom line, ;; called the "minibuffer". We will generally use `C-x C-e', ;; as we don't want to clutter the buffer with useless text. ;; `setq' stores a value into a variable: (setq my-name "Bastien") ;; `C-x C-e' => "Bastien" (displayed in the mini-buffer) ;; `insert' will insert "Hello!" where the cursor is: (insert "Hello!") ;; `C-x C-e' => "Hello!" ;; We used `insert' with only one argument "Hello!", but ;; we can pass more arguments -- here we use two: (insert "Hello" " world!") ;; `C-x C-e' => "Hello world!" ;; You can use variables instead of strings: (insert "Hello, I am " my-name) ;; `C-x C-e' => "Hello, I am Bastien" ;; You can combine sexps into functions: (defun hello () (insert "Hello, I am " my-name)) ;; `C-x C-e' => hello ;; You can evaluate functions: (hello) ;; `C-x C-e' => Hello, I am Bastien ;; The empty parentheses in the function's definition means that ;; it does not accept arguments. But always using `my-name' is ;; boring, let's tell the function to accept one argument (here ;; the argument is called "name"): (defun hello (name) (insert "Hello " name)) ;; `C-x C-e' => hello ;; Now let's call the function with the string "you" as the value ;; for its unique argument: (hello "you") ;; `C-x C-e' => "Hello you" ;; Yeah! ;; Take a breath. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ;; Now switch to a new buffer named "*test*" in another window: (switch-to-buffer-other-window "*test*") ;; `C-x C-e' ;; => [screen has two windows and cursor is in the *test* buffer] ;; Mouse over the top window and left-click to go back. Or you can ;; use `C-x o' (i.e. hold down control-x and hit o) to go to the other ;; window interactively. ;; You can combine several sexps with `progn': (progn (switch-to-buffer-other-window "*test*") (hello "you")) ;; `C-x C-e' ;; => [The screen has two windows and cursor is in the *test* buffer] ;; Now if you don't mind, I'll stop asking you to hit `C-x C-e': do it ;; for every sexp that follows. ;; Always go back to the *scratch* buffer with the mouse or `C-x o'. ;; It's often useful to erase the buffer: (progn (switch-to-buffer-other-window "*test*") (erase-buffer) (hello "there")) ;; Or to go back to the other window: (progn (switch-to-buffer-other-window "*test*") (erase-buffer) (hello "you") (other-window 1)) ;; You can bind a value to a local variable with `let': (let ((local-name "you")) (switch-to-buffer-other-window "*test*") (erase-buffer) (hello local-name) (other-window 1)) ;; No need to use `progn' in that case, since `let' also combines ;; several sexps. ;; Let's format a string: (format "Hello %s!

" "visitor") ;; %s is a place-holder for a string, replaced by "visitor". ;;

is the newline character. ;; Let's refine our function by using format: (defun hello (name) (insert (format "Hello %s!

" name))) (hello "you") ;; Let's create another function which uses `let': (defun greeting (name) (let ((your-name "Bastien")) (insert (format "Hello %s!



I am %s." name ; the argument of the function your-name ; the let-bound variable "Bastien" )))) ;; And evaluate it: (greeting "you") ;; Some function are interactive: (read-from-minibuffer "Enter your name: ") ;; Evaluating this function returns what you entered at the prompt. ;; Let's make our `greeting' function prompt for your name: (defun greeting (from-name) (let ((your-name (read-from-minibuffer "Enter your name: "))) (insert (format "Hello!



I am %s and you are %s." from-name ; the argument of the function your-name ; the let-bound var, entered at prompt )))) (greeting "Bastien") ;; Let's complete it by displaying the results in the other window: (defun greeting (from-name) (let ((your-name (read-from-minibuffer "Enter your name: "))) (switch-to-buffer-other-window "*test*") (erase-buffer) (insert (format "Hello %s!



I am %s." your-name from-name)) (other-window 1))) ;; Now test it: (greeting "Bastien") ;; Take a breath. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; ;; Let's store a list of names: (setq list-of-names '("Sarah" "Chloe" "Mathilde")) ;; Get the first element of this list with `car': (car list-of-names) ;; Get a list of all but the first element with `cdr': (cdr list-of-names) ;; Add an element to the beginning of a list with `push': (push "Stephanie" list-of-names) ;; NOTE: `car' and `cdr' don't modify the list, but `push' does. ;; This is an important difference: some functions don't have any ;; side-effects (like `car') while others have (like `push'). ;; Let's call `hello' for each element in `list-of-names': (mapcar 'hello list-of-names) ;; Refine `greeting' to say hello to everyone in `list-of-names': (defun greeting () (switch-to-buffer-other-window "*test*") (erase-buffer) (mapcar 'hello list-of-names) (other-window 1)) (greeting) ;; Remember the `hello' function we defined above? It takes one ;; argument, a name. `mapcar' calls `hello', successively using each ;; element of `list-of-names' as the argument for `hello'. ;; Now let's arrange a bit what we have in the displayed buffer: (defun replace-hello-by-bonjour () (switch-to-buffer-other-window "*test*") (goto-char (point-min)) (while (search-forward "Hello") (replace-match "Bonjour")) (other-window 1)) ;; (goto-char (point-min)) goes to the beginning of the buffer. ;; (search-forward "Hello") searches for the string "Hello". ;; (while x y) evaluates the y sexp(s) while x returns something. ;; If x returns `nil' (nothing), we exit the while loop. (replace-hello-by-bonjour) ;; You should see all occurrences of "Hello" in the *test* buffer ;; replaced by "Bonjour". ;; You should also get an error: "Search failed: Hello". ;; ;; To avoid this error, you need to tell `search-forward' whether it ;; should stop searching at some point in the buffer, and whether it ;; should silently fail when nothing is found: ;; (search-forward "Hello" nil t) does the trick: ;; The `nil' argument says: the search is not bound to a position. ;; The `t' argument says: silently fail when nothing is found. ;; We use this sexp in the function below, which doesn't throw an error: (defun hello-to-bonjour () (switch-to-buffer-other-window "*test*") (erase-buffer) ;; Say hello to names in `list-of-names' (mapcar 'hello list-of-names) (goto-char (point-min)) ;; Replace "Hello" by "Bonjour" (while (search-forward "Hello" nil t) (replace-match "Bonjour")) (other-window 1)) (hello-to-bonjour) ;; Let's colorize the names: (defun boldify-names () (switch-to-buffer-other-window "*test*") (goto-char (point-min)) (while (re-search-forward "Bonjour \\(.+\\)!" nil t) (add-text-properties (match-beginning 1) (match-end 1) (list 'face 'bold))) (other-window 1)) ;; This functions introduces `re-search-forward': instead of ;; searching for the string "Bonjour", you search for a pattern, ;; using a "regular expression" (abbreviated in the prefix "re-"). ;; The regular expression is "Bonjour \\(.+\\)!" and it reads: ;; the string "Bonjour ", and ;; a group of | this is the \\( ... \\) construct ;; any character | this is the . ;; possibly repeated | this is the + ;; and the "!" string. ;; Ready? Test it! (boldify-names) ;; `add-text-properties' adds... text properties, like a face. ;; OK, we are done. Happy hacking! ;; If you want to know more about a variable or a function: ;; ;; C-h v a-variable RET ;; C-h f a-function RET ;; ;; To read the Emacs Lisp manual with Emacs: ;; ;; C-h i m elisp RET ;; ;; To read an online introduction to Emacs Lisp: ;; https://www.gnu.org/software/emacs/manual/html_node/eintr/index.html ;; Thanks to these people for their feedback and suggestions: ;; - Wes Hardaker ;; - notbob ;; - Kevin Montuori ;; - Arne Babenhauserheide ;; - Alan Schmitt ;; - LinXitoW ;; - Aaron Meurer