Emacs Tips and Tricks

Emacs Tips and Tricks

23 Sep 2017
programming, tools

Emacs Tips and Tricks #

To Learn About #

  • ☒ Company-mode (completion framework for lots of stuff)
  • ☒ YASnippets (templates)
  • ☒ Auto-YASnippets (something like that—I installed it for temporary templates)
  • ☒ Alchemist mode (integrates with company mode—tooling for Elixir)
  • ☐ What do M-. and M-, do?
  • font-lock-add-keywords would let me add new keywords to a language
  • ☐ hi-lock
  • ☐ highlight-phrase, unhighlight-regex
  • Registers
  • ☐ Auto-loading packages to make startup time shorter

Things that make me happy #

  • Undo in region (just highlight something and hit undo)
  • Generate Backus-Nauer Forms with a slightly modified syntax with ebnf-eps-buffer

Helm #

You can filter buffers by pattern with Helm. Type: @pattern to find buffers matching pattern. If you want to have spaces in the pattern, you must escape them with a backslash.

Searching with the Silver Searcher #

You’ll need helm-ag. After searching, you get the following keybindings:

Key Bindings #
Key Action
C-c o Open other window
C-l Search in parent directory
C-c C-e Switch to edit mode
C-x C-s Save ag results to buffer(Ask save buffer name if prefix key is specified)
C-c C-f Enable helm-follow-mode
C-c >, right Move to next file
C-c <, left Move to previous file
C-c ? Show help message
Edit mode keymap #
Key Action
C-c C-c Commit changes
C-c C-k Abort
C-c C-d Mark delete line
C-c C-u Unmark
Saved buffer keymap #
Key Action
RET Jump to current line posion
C-o Jump to current line posion in other window
g Update result

Registers #

Any letter can be a register. (Uppercase and lowercase are distinct.) In the follinwg examples, <r> represents a register name.

Working with the point:

  • C-x r SPC <r> Store point in register (mnemonic: C-SPC saves current mark)
  • C-x r j <r> Jump to point saved in register (mnemonic: jump)

Working with text:

  • C-x r s <r> Save region into register
  • C-x r i <r> Insert contents of register (also works for numbers)

Working with numbers:

  • C-u NUMBER C-x r n <r> Save a number
  • C-u NUMBER C-x r + <r> Increment register <r> by NUMBER (if C-u NUMBER omitted, increments by 1)


  • C-x C-k r <r> Save last kbd macro to register

Special Modes #

Racket #

Start everything off right with M-x run-geiser RET racket RET.

  • C-c C-d TAB Open up documentation for command under point

Calc #

  • TAB rotate

Web Mode #

I do a fair amount of web programming. web-mode is awesome! There are way too many keystrokes for me to list. Here are my favorite, though:

  • C-c C-e / Close element. (Mnemonic: C-element / (for closing HTML tags))

  • C-c C-f Fold. Collapses current tag and subtree. Same keystroke to unfold.

Markdown Mode #

  • C-c C-] Complete markup of element. (e.g. sticks “###” at the end of a line on a h3 element

  • TAB When called on a heading, collapses/expands the heading.

  • Shift-TAB Cycles global folding/visibility

Text keys: (all start with C-c C-s)

  • C-c C-s s Make current word/region bold (s is for strong)

  • C-c C-s e Italics. (e for emphasis)

Bookmarks #

  • I installed the bm module. Run bm-toggle to book mark a line visually.

Native bookmarks:

  • C-x r m New bookmark. Prompts for a name. Mnemonic: “mark”

  • C-x r b Jump to a bookmark. Mnemonic: “bookmark”, or “back to bookmark”

  • C-x r l List bookmarks.

Jumping to a bookmark will do so in the current window, and will put you where the point last was in that buffer. If you are already in the buffer, then it will jump to the point where to bookmark was set.

Bookmarks persist over a session—I’m not sure where the file is, but they do get stored in some file.

Expansion #

M-/ will do “dynamic expansion”—if there is a word in one of the buffers of the current session that starts with whatever your cursor is on, it will expand to that word. Multiple consecutive invocations of this function will cycle through available expansions.

There’s a way to do manual expansion, but I don’t know it.

Window enlargements #

I’ve defined a few nice functions. Here they are:

(defun sticky-enlarge-window-horizontally (prefix)
  (interactive "P")
  (enlarge-window-horizontally (if prefix (car prefix) 1))
  (unless (current-message)
    (message "(Use `[' and `]' to adjust window size)"))
  (let ((map (make-sparse-keymap)))
    (define-key map (kbd "]") 'enlarge-window-horizontally)
    (define-key map (kbd "[") 'shrink-window-horizontally)
    (set-transient-map map t)))

(defun sticky-shrink-window-horizontally (prefix)
  (interactive "P")
  (shrink-window-horizontally (if prefix (car prefix) 1))
  (unless (current-message)
    (message "(Use `[' and `]' to adjust window size)"))
  (let ((map (make-sparse-keymap)))
    (define-key map (kbd "]") 'enlarge-window-horizontally)
    (define-key map (kbd "[") 'shrink-window-horizontally)
    (set-transient-map map t)))

(define-key global-map (kbd "C-x }") 'sticky-enlarge-window-horizontally)
(define-key global-map (kbd "C-x {") 'sticky-shrink-window-horizontally)
(define-key global-map (kbd "<f7>") 'shrink-window-horizontally)
(define-key global-map (kbd "<f8>") 'balance-windows)
(define-key global-map (kbd "<f9>") 'enlarge-window-horizontally)

Functions #

  • toggle-truncate-lines will toggle how long lines are displayed

  • C-x C-d is essentially ls — lists the contents of a directory

  • C-u M-| pipe region to a shell command and replace it with the output

    You can get sweet sed-like behavior with something like this:

     perl -ne 's/^(\d+)\.(\d+)/<<1 Thes. $1:$2>>/g; print'

Macro wisdom #

Put cursor where it is supposed to go, begin recording (C-x (), do thingy, isearch to next location, and then stop recording. (C-x )) This lets you see what is going to be edited next, and hit C-s C-s if you want to skip to the next match.

<f3> Is a very fancy key. Normally, it will begin recording a macro. Once you are defining a macro, hitting <f3> again will insert the current macro counter.

<f4> is its best friend. Hitting <f4> while defining a macro will end the macro. Hitting <f4> otherwise will then run the last defined keyboard macro. Running C-u <f4> runs the second macro in macro ring. Running C-u 4 <f4> runs the first macro 4 times. (Adjust 4 as you will.)

You can use Lisp inside of a macro. For example, to insert incrementing numbers, do:

M-: (setq x 1) RET
C-u M-: x RET
M-: (setq x (+ x 1))
<whatever else>

You can repeat a macro until an error is signaled with C-u 0 C-x e.

You can also run apply-macro-to-region-lines (C-x C-k r) to fire a macro on every line in the region.

To prompt a user for input while writing a macro, do: C-u C-x q. This is a variant of C-x q which queries the user.

Recursive editing #

Hitting C-r will enter a recursive editing level when the macro is run, but not while you are recording.

C-x q enters a query state: y continues to execute the macro, n aborts the current iteration, and q aborts all together.

C-u C-x q lets you enter in some text.

To finish recursive editing, type C-M-c. To abort and halt execution, type C-].

Rectangles #

To select text in a rectangle, use C-x SPC. The region will then highlight like a rectangle. The kill and yank commands will work like normal (i.e. hitting C-k will kill the rectangle.)

  • C-x r M-w Copy rectangle as kill. (Think M-w)

  • C-x r N Inserts numbered lines in the rectangle. Accepts a prefix argument to change at what number the lines start at.

  • M-x string-insert-rectangle Prompts for a string and inserts it at the current rectangle. So you can go from this:


    to this:

     - one
     - two
     - three
     - four

    by setting the mark on the o of one, then moving to the f in four, then running the command.

Misc. Keystrokes #

  • C-x <right arrow> cycle through buffers

  • C-x C-q toggle read-only mode in current buffer

  • C-x C-; to set comment column to cursor’s current column

  • C-x C-h Really <any prefix> C-h shows a listing of all possible completions after the prefix character.

  • C-x 8 RET Insert arbitary unicode character by name. You can insert snowmen like this!

  • C-x 8 <char> There are a bunch of characters that you can insert after this. “<” will insert “«”

  • C-x n n Only displays the region. Good for focusing. Use C-x n w to display everything.

  • C-x $ To hide lines in the current buffer, type ‘C-x $’ (‘set-selective-display’) with a numeric argument N. Then lines with at least N columns of indentation disappear from the screen.

  • C-u Prefix argument. The default is 4. If you want to grow the current window by, say, 15 lines, do following: C-u 15 C-x ^.

  • C-u <number> <key> Repeats <key> <number> times. It’s different for inserting digits. If you wanted to insert 5 seven times, type C-u 7 C-u 5.

  • C-x C-k C-i Inserts the current value of the keyboard macro counter and increments it. When C-u proceeds the command, the previous value is inserted, and the counter is not updated. A prefix argument specifies a different increment.

  • C-x C-k C-c Prompts for the initial value of the keyboard macro. Must be called prior to starting macro definition to be used this way. It has another behavior if called during macro definition. See this page for help.

  • C-x C-k n Give the last kbd macro a name, which you can then call

  • ESC-^ Join this line to the previous and fix up whitespace at join. Useful if auto-fill-mode was turned on and you need to unwrap a line.

  • <f1> Run help

  • <f2> Appears to be a prefix command, much like C-x.

  • <f10> Opens the menu. As in, the one at the top of the screen that you never have actually used. With ACTUAL GRAPHICS!!

  • C-x RET f Allows you to set the encoding when saving the file. Useful for stripping bad line endings in DOS files.

Dired #

  • C-o In dired, opens the file the cursor is on in the other window.

Occur #

  • C-u M-s o <pattern> RET Copies all strings mattching <pattern> (if you use .*thingy.* it will copy the whole line with “thingy” in it) into buffer called *Occur* ### Regexes

Not like Perl. In (?:aaa|bbb), the characters (, ), and | all match themselves. If you want perl-like behavior, escape them: \(?:aaa\|bbb\).

But when you want to type that in a string literal, use "\\(?:aaa\\|bbb\\)".

Character Classes #

Some common character classes:

  • . works as expected (any char)
  • [[:ascii:]]+ any ascii character
  • [_A-Za-z0-9]+ letters, digits, underscores
  • "\([^"]+\)" capture text between double quotes (not accounting for escaped chars)

Regex search and replace: #

M-x replace-regexp
Replace regexp: right\|left
Replace regexp with: \,(if (equal "right" \&amp;) "left" "right")

Looks like the \,(...) syntax says “evaluate me”. :)

Regex search and replace with captured bit #

M-x replace-regexp
Replace regexp: subject(\([A-Za-z]+\))
Replace regexp with: \1

That gets subject(*), and retuns *

Programming Languages #

C #

Compile (using make -k) with M-x compile.

Any errors will show up in a special buffer; visit with C-x `