Emacs Notes & Tips

#1. Making Alt the Meta key under X. Put this in the $HOME/.Xmodmap file ! Rebind keys to permit Alt key to be Meta in Emacs. clear mod1 clear mod4 keycode 115 = Alt_L keycode 64 = Meta_L keycode 113 = Meta_R add mod1 = Meta_L Meta_R add mod4 = Alt_L ! Make the CapsLock key a Ctrl key remove Lock = Caps_Lock keysym Caps_Lock = Control_L add Control = Control_L and run xmodmap on it on X startup. Confirm the keycodes with xev first. #2. Differentiating between X mode and Console mode. The function display-color-cells will return the number of supported colors, which is normally 8 on a tty, 16 on MS-DOS and MS-Windows text-mode displays, and a much larger number in the GUI versions. #3. How do I really indent? Typically M-i is bound to the function tab-to-tab-stop, which will tab to the next tab stop. The tab stops are controlled via the tab-stop-list variable. #4. How do I change the tab width? If you don't like the default tab stops, reset them. ;; to set the tab stops (defun set-tab-stops (n) "Set the tab stops at intervals specified by the argument n." (let ((tab-stops '()) (i n)) (while (< i 100) (setq tab-stops (cons i tab-stops)) (setq i (+ i n))) (setq tab-stops (reverse tab-stops)))) ;; reset the tab stops to every 4 (setq tab-stop-list (set-tab-stops 4)) If you want to change the size of a displayed tab, change the value of the tab-width variable. (setq-default tab-width 4) This just changes the default, so it can be overridden by a buffer-specific variable using plain setq. #5. How do I translate tabs to spaces? Reset the value of the indent-tabs-mode variable to nil to prevent inserting tab characters while you work. If you want to get rid of existing tab characters, call the untabify function on the region. Select the entire buffer if you want to do it all. C-x h M-x untabify RET #6. How do I view tab characters and newlines like with Vi's :set list? There is nothing built-in. You can use the whitespace.el package, or try something simpler like the following. ;; custom miscellaneous functions (defun vi-list () "Simulate a :set list in Vi." (interactive) (standard-display-ascii ?\t "^I") (standard-display-ascii ?\ "$\ ") ) (defun vi-nolist () "Simulate a :set nolist in Vi." (interactive) (standard-display-ascii ?\t "\t") (standard-display-ascii ?\ "\ ") ) #7. How do I modify the default load-path used to find Emacs packages? Change the load-path variable, like so: (setq load-path (cons "/home/msoulier/elisp" load-path)) #8. How do I jump to a matching parenthesis like Vi's % command? Remap the % to do this if it's sitting on a parenthesis, and to call self-insert-command otherwise. Granted, this means you'll never be able to insert a % in front of a parenthesis without extra keystrokes, but how often does that happen? ;; for simulating Vi's % capability (defun match-paren (arg) "Go to the matching paren if on a paren; otherwise insert %." (interactive "p") (cond ((looking-at "\\s\(")(forward-list 1)(backward-char 1)) ((looking-at "\\s\)")(forward-char 1)(backward-list 1)) (t (self-insert-command (or arg 1))))) #9. How do I run some commands whenever a certain mode is set? Add your own personal function to the hook for that mode, which is typically by the name of <mode>-hook. For example, here's how to run something when you enter python-mode. (defun my-python-mode-hook () "My personal python mode customizations." (message "Setting personal python-mode customizations...") ) (add-hook 'python-mode-hook 'my-python-mode-hook) #10. How do I customize the colours and settings in the emacs modes? Most variables are available through the customization API. Try the menu option "Edit->Customize Emacs", or access the customization functions through M-x customize- SPACE #11. How do I jump the cursor to the top of the window, and the bottom, like Vi's H and L commands? You'll have to roll your own. (defun point-to-top () "Put cursor on top line of window, like Vi's H." (interactive) (move-to-window-line 0)) (defun point-to-bottom () "Put cursor at bottom of last visible line, like Vi's L." (interactive) (move-to-window-line -1)) #12. How do I scroll the window without moving the cursor? You'll have to roll your own. (defalias 'scroll-ahead 'scroll-up) (defalias 'scroll-behind 'scroll-down) (defun scroll-n-lines-ahead (&optional n) "Scroll ahead N lines (1 by default)." (interactive "P") (scroll-ahead (prefix-numeric-value n))) (defun scroll-n-lines-behind (&optional n) "Scroll behind N lines (1 by default)." (interactive "P") (scroll-behind (prefix-numeric-value n))) (global-set-key "\C-q" 'scroll-n-lines-behind) (global-set-key "\C-z" 'scroll-n-lines-ahead) ;; don't forget to move the "C-q" you just clobbered. (global-set-key "\C-x\C-q" 'quoted-insert) #13. The "C-x o" keystroke is a pain, especially when you have more than two windows open. Is there a better way to do this? The other-window function goes forward through the window list, but a function to go backwards would help. other-window will with the right argument, so try this: (defun other-window-backward (&optional n) "Select Nth previous window." (interactive "P") (other-window (- (prefix-numeric-value n)))) (global-set-key "\C-x\C-n" 'other-window) (global-set-key "\C-x\C-p" 'other-window-backward) #14. How do I make the compile commands easier to use? If you're on a PC keyboard with functions keys, try something like this: (global-set-key [f4] 'compile) (global-set-key [f5] 'switch-to-buffer) (global-set-key [f7] 'next-error) (global-set-key [f8] 'previous-error) #15. How do I delete blank lines from a file? C-x C-o is usually bound to the delete-blank-lines function. Read about it with C-h f delete-blank-lines RET. #16. How do I tell what face a piece of text belongs to? Put the cursor on the text in question and enter: M-x list-text-properties-at RET #17. How do I tell when Emacs is garbage collecting? Set the variable garbage-collection-messages to t, and watch the *Messages* buffer. #18. After I haven't done anything in Emacs for a while, the fontification suddenly changes. What's going on? C-h f lazy-lock-mode RET #19. How do I find documentation on the available functions in Emacs? Use M-x apropos RET, or search the info documentation. Note that "C-h a" is not equivalent to apropos mode, as the former will only tell you about commands (ie. interactive functions). #20. How do I control where the line wraps in auto-fill mode? fill-column's value is 70 Documentation: Column beyond which automatic line-wrapping should happen. Automatically becomes buffer-local when set in any fashion. You can customize this variable. #21. Sometimes I get an error about files that I've saved with Emacs, where it complains that the file doesn't have a newline. Is this a problem? How do I fix it? It's not really a problem, but you can make sure a newline is inserted with the following in your ~/.emacs: ;; make edited files end with a carriage return (setq require-final-newline t) #22. When I cursor past the end of the file, new lines are added to the buffer. I don't like that, how do I turn it off? Put this in your ~/.emacs: ;; don't let next-line add new lines at end of file (setq next-line-add-newlines nil) #23. When I compile, the compile window doesn't scroll along with the output. Is there a way to fix this? Yes. Set the variable compilation-scroll-output to true. ie. (setq compilation-scroll-output t) #24. How to get the tramp package working with password logins. in .emacs: ; Configure Tramp for remote editing (require 'tramp) (setq tramp-default-method "sm") ; ssh with mimedecode You can also control this on a per-connection basis with: /r@sm:me@remotehost:/path/to/file #25. How do I handle files from multiple operating systems? You can choose the operating system coding system that you wish to use with the set-buffer-file-coding-system function. ie. C-x RET f unix/dos/mac #26. In Emacs21, how do I control the amount of time Emacs waits before updating the fontification of my file? Customize the variable jit-lock-stealth-time. #27. How do I tell if I have a conflicting site file of some kind? Try this: emacs -q -batch -f list-load-path-shadows If it prints anything at all, it means you have conflicting Lisp files on your load-path. #28. How do I get rid of the menu bar and/or the tool-bar? (menu-bar-mode nil) (tool-bar-mode nil) Or just run the functions with no args to toggle them on the current frame. #29. How do I get the hostname of the machine that Emacs is running on? The variable system-name stores the hostname for you. ie. (if (equal system-name "homebox") (do-home-stuff) (do-work-stuff)) #30. How do I run a shell command and capture the output? The old way is to call the shell-command function in a temp buffer, which permits you to manipulate the output easily as if it were any Emacs buffer. (with-temp-buffer (shell-command "hostname" t) (goto-char (point-max)) (delete-char -1) (buffer-string)) Another way is to simply call shell-command-to-string, but this string will contain all additional characters from the output, like newline characters. Thankfully, we can now call shell-command with an extra true parameter to have it included in our current buffer. ie. (shell-command "cal" t) Interactive, just use a prefix command. ie. C-u M-! cal RET #31. How do you keep the shell-mode from scrolling by half a screen when it reaches the bottom? This should do it: (setq scroll-conservatively 1) #32. How do I set up AucTex mode for editing LaTeX? (require 'tex-site) ; Load AUC-TeX (setq-default TeX-master nil) ; Query for master file (setq TeX-parse-self t) ; Parse file after loading (setq TeX-auto-save t) ; Automatically save style It's also important to ensure that the font-latex.el package is being loaded as well, if you want the fontifying to be correct. #33. Can I set up Emacs to autodetect changes to files that I'm editing and reload them? Yes. On a single buffer use auto-revert-mode. If you want to enable it on all buffers, issue global-auto-revert-mode. Customize the minor mode string like so: (add-hook 'global-auto-revert-mode-hook (lambda () (setq global-auto-revert-mode-text " GAutRev"))) #34. How can I force a reload on all buffers? Code it. You can loop through the buffer list. (let ((lst (buffer-list))) (while lst (if (buffer-file-name (car lst)) (revert-buffer (car lst))) (setq lst (cdr lst)))) #35. Is there a way to determine if the point is in a comment region or not? (if (equal face-at-point 'font-lock-comment-face) (comment-foo) (normal-bar)) This is the extremely simple version of course, which could be used to code a simple predicate for this very question. (defun in-comment-block () (if (equal face-at-point 'font-lock-comment-face) t nil)) Or, if you want to get very generic, you can use this piece of work from Toby Haynes, to permit generic determination of ones syntactic context. (defun syntactic-context () "Check in which syntactic context point is. Return nil if no special context meaning, otherwise 'string if within a string, 'comment if within a line-comment and 'block-comment if within a block-comment." (let* ((beg (save-excursion (beginning-of-defun) (point))) (state (save-excursion (parse-partial-sexp beg (point))))) (cond ((nth 3 state) 'string) ((nth 4 state) (if (member major-mode '(c-mode c++-mode java-mode jde-mode)) (if (nth 7 state) 'comment 'block-comment) 'comment)) (t nil)))) #36. How do I get Emacs to stop beeping at me? Change the bell to a visual one, just like an xterm, like so: (setq visible-bell t) #37. I was trying to use psgml-mode to edit my HTML, but the indenting seems all wrong. Did I do something wrong? Possibly. Make sure that you have a proper document type definition at the beginning of the page. For HTML, something like this should do: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"> #38. How do I turn off colour in Emacs? I don't want it when I'm in a tty. To turn off colour, this should do it. (tty-color-clear) (tty-set-up-initial-frame-faces) Ordering is important here, so you might have to put this in your after-init-hook. A more complete solution would be like so, from Kai ?: ;; Support different color scheme (defun kai-dark-background (dummy) (add-to-list 'default-frame-alist '(background-mode . dark)) (setq-default frame-background-mode 'dark) (mapcar 'frame-set-background-mode (frame-list))) (add-to-list 'command-switch-alist '("-dark" . kai-dark-background)) (defun kai-light-background (dummy) (add-to-list 'default-frame-alist '(background-mode . light)) (setq-default frame-background-mode 'light) (mapcar 'frame-set-background-mode (frame-list))) (add-to-list 'command-switch-alist '("-light" . kai-light-background)) You might wish to try with "emacs -dark" and "emacs -light" to see whether that helps. #39. When I loaded a really large file, I got an error stating "maximum buffer size exceeded". What's up with that? This is a limitation of the font-lock-maximum-size variable, which controls the maximum size of a buffer for fontification purposes. The default size is 256000. You can increase the size, or customize it by mode as an alist, or even nil it to make it irrelevant. C-h v font-lock-maximum-size RET for more information. #40. Is it possible to add keywords to cc-mode, so it recognizes more of my custom types? Sure. Use the font-lock-add-keywords function. (font-lock-add-keywords 'c-mode '(("\\<\\(FIXME\\)" 1 font-lock-warning-face t))) Change FIXME and the face to whatever you want. #41. How do I eval some arbitary lisp code? The simplest way is M-: (eval-expression), but you can also put any lisp expression in any buffer, move the cursor to the end of it, and hit C-x C-e (eval-last-sexp). See also: http://tiny-tools.sourceforge.net/emacs-keys.html