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Introduction to Emacs

Introduction

Why Emacs?

The Most Customize-able editor

Design philosophy focused on efficiency and versatility

40 years of active development means its functionality is mature and well designed

Tons of extremely well developed plugins for basically every use case

Designed to be self documenting, so you can learn as you use it

Emacs can edit most of its own code from within its editor, without ever exiting

Disclaimer

Emacs is complicated, and has many more functions than you could ever reasonably learn

Using Emacs efficiently requires you to learn tons of keyboard shortcuts, and this presentation contains many

Unless you have a perfect memory, you will forget almost all of them

As you use Emacs for your own actual work, you will remember the functionality that you use most

If you discover you are doing some repetitive task while coding, 100% chance Emacs has a solution!

Basic Commands

How To Get Help

To find out what a key binding does, use C-h k

To find out what a certain function does, use C-h f

To learn about the help features in general, use C-h ?

How to Read Emacs Key Bindings

All default Emacs commands use 1 or 2 modifier keys, called Control and Meta

By default, Control is bound to Ctrl and Meta is bound to Alt. (Sometimes Mac users use command as Meta)

Emacs also offers 2 other modifiers not used by default called Super and Hyper, so you can bind a command to hyperspace!

The reason for these weird Meta, Super, Hyper key stuff is due to the fact Emacs was originally made for Lisp machines, with strange keyboards

C-x means “press x while holding control”

M-x means “press x while holding meta”

An alternate way to press M-x is to first press escape then press x, which is especially useful when using Emacs on really old systems

C-M-x is just pressing x while holding both control and meta

Some commands will require you to type text after, which will be prompted on the bottom bar.

Four Extremely Useful Commands

Save!!!!!! : C-x C-s

Open File!!!!!! : C-x C-f

Cancel any command! If you are ever stuck in a command just hit C-g

Auto-complete: Tab when used with other commands, or M-/ in a buffer!

Basic Movement

Characters, Words, and Lines

Forward Char: C-f

Backward Char: C-b

Next Line: C-n

Previous Line: C-p

Beginning of Line: C-a

End of Line: C-e

Try moving around whatever file you have open, keyboard only

Delete Character: C-d

Forward Word: M-f

Backward Word: M-b

Delete Word: M-d

S-Expressions (Sexp)

Represent all forms of balanced pairs such as (asda) {asdads} “adsada”, etc.

Sometimes language modes may define what is meant by an Sexp

e.g. Python mode may treat single quotes as a balanced pair whole while Lisp would not

C-M-f and C-M-b moves across an S-expression

C-M-n and C-M-p will move across the next/previous set of balanced expressions

The main thing to notice is that C- corresponds to characters, M- to words, and C-M- to Sexp

Cut and Paste (Kill and Yank)

Emacs pre-dates the idea of cut, copy, and paste as Ctrl-{x,c,v}

The hotkeys Emacs uses instead were originally chosen for efficiency, so it may seem odd by modern standards

If you really badly want to use C-x, C-v, etc. something called CUA mode exists just for you
From here on all hotkeys will assume CUA mode was not enabled

Kill is equivalent to cut, Yank = paste, and Copy is equivalent to a kill then yank (sort of)

Instead of a clipboard, Emacs has a kill ring storing the last (default of 60) kills

You can select a region by placing a mark and then moving your cursor

Place mark on cursor: C-Space

Place rectangular mode mark: C-x Space

Kill marked region: C-w

Kill to end of line: C-k

Kill character: C-d

Kill word: M-d

Kill sentence: M-k

Kill Sexp: C-M-k

“Copy” marked region: M-w

Yank: C-y

Yank from kill ring: M-y

Get a hang of yank and kill, try moving around function definitions in one of the source files

Incremental Search

There are so many different (most useful) key bindings I can only mention the basics

Search Forward: C-s expression-to-search (repeated C-s goes through next words)

Search Backward: C-r expression-to-search

Search Forward with Regexp (Seriously try to get used to regex its worth it): C-M-s

Cancel Search (and generally cancel most things), returning to start: C-g

Exit search on current word: RET

While searching, add rest of word to search string: C-w

Query Replace (like find and replace): M-% and use y or n to confirm replacements

Query Replace with Regexp: C-M-%

Misc. Bonus Commands That May Be Useful

Go to end of buffer: M->

Go to start of buffer: M-<

Scroll up a page: C-v

Scroll down a page: M-v

Center screen on cursor: C-l (multiple uses cycles putting cursor on top and bottom of screen)

Reposition window by having emacs guess what will show the most useful information: C-M-l

Repeat previous command: C-x z (subsequently pressing z continues repeating)

Attempt to autocomplete based on what is in current buffer: M-/ (some modes overwrite this to make it smarter)

Exchange cursor with mark: C-x C-x

NOTE: Linux Terminal by default actually uses many of these movement bindings!

Buffers and Windows (and why they are better than tabs)

Emacs does not use tabs like other editors, instead all text is stored in a “buffer”

Emacs may have many buffers open, and they can be viewed via a “window”

All buffers usually have a name, and you can switch to buffers by name

This means no matter how many buffers you have open, it is just as easy to find the right one

You can rename your current buffer with: M-x rename-buffer RET

The line of text at the bottom that opens when you use commands like search is called the mini buffer

The flexibility offered by using buffers together with windows is MUCH better than most IDEs

Change buffer: C-x b

Kill buffer: C-x k

Split window horizontally: C-x 2

Split window vertically: C-x 3

Close all windows but current: C-x 1

Close current window: C-x 0

Swap cursor to next window: C-x o

Enlarge window vertically and horizontally respectively: C-x }, C-x ^

Open up every single file in examples to a buffer, and have at least 3 open at the same time.

Now add a line of text to every single file (e.g. a code comment) without touching your mouse

Undo in Emacs (If you don’t like this undo-tree is a great alternative, especially for former Vim users)

All actions in Emacs are stored in a stack, and undo pops the previous action off the stack

Undo: C-x u or C-_

In order to allow undoing multiple things, a continuous sequence of undoes ignores previous undoes

Commands that do not actually edit the buffer are never undone, but they DO remain in the stack

This means that to undo an undo, you must first break the chain of undoes with another action

The most common way of doing this is by just pressing C-f followed by and undo

Undo tree is a plugin that copies Vim’s version of undo, using a tree instead of a stack

It also has a dedicated redo button saving the confusion with C-f

Giving a Parameter to Commands (Universal Argument!)

Every hotkey in Emacs corresponds to a function that can be used with M-x function-name RET

Most functions don’t take a parameter, but can take a Universal argument N to repeat N times

To give a command a universal argument of N: C-u N (insert command here)

Examples: C-u 3 C-f moves forward 3 characters. C-u 13 M-c will capitalize the next 13 words

A shorthand for C-u N is just C-[that #] (e.g C-3 = C-u 3). C-u on its own is the same as C-u 4

Occasionally some functions will take a parameter to do something different than repeat

The help for any given function will specify if it takes an argument (accessed with C-h f)
These functions will have an &optional tag and will clarify in description what it does
Usually in these cases passing any argument regardless of value will give some alternate behavior

Quickly undo all changes you made to one of the buffers using a universal parameter

Editing Modes

Major Modes

No matter what Emacs runs with exactly 1 major mode, defaulted to “Fundamental Mode”

In practice fundamental mode is never used, Emacs has a mode for just about everything from poetry to SystemVerilog

Emacs will automatically pick the mode based on file type, but can be changed manually with M-x modename-mode

The Major Mode determines the overall behavior of the editor

It usually enables many new keybindings specific to the mode, and replaces others (e.g. changes newline behavior for Python)

Many modes will offer more advanced features such as Org mode which has headings and can track your calender/ do much more!

Minor Modes

Unlike major modes, you can have any number of minor modes enabled

To display all the information about your current modes, press C-h m

Make a new file, and copy in every single mode you have enabled into that file

Most minor modes are disabled by default, exceptions include Transient Mark Mode as mentioned before

Some useful default minor modes:

linum-mode for displaying line numbers

Electric-Pair and Electric-indent gives IDE like indenting and balanced pairs

Transient-Mark which allows placing a mark to select a region

Show-Paren highlights matching parenthesis

Some minor modes are global meaning always active, others are local to a certain buffer

A common way of using minor modes is enabling them only for certain major modes, we will see how to do this soon

To enable or disable modes manually, simply use M-x mymode-mode

Try disabling and then re-enabling Transient Mark Mode, and see how it changed the behavior of C-Space

Advanced Commands and Features

Macros

Macros allow you to record actions to replay later, which can be extremely useful and time saving

To begin, just press C-x ( and Emacs will record all further actions. C-x ) ends recording

To then execute the recorded macro, use C-x e

This works really well in conjunction with the Universal Parameter C-u to repeat the macro

You can then give the macro a name for the session with C-x C-k n, or bind it to a key with C-x C-k b

After doing that, M-x insert-kbd-macro will create a Lisp function for the macro which you can store

Regular Expressions

Most often used alongside searches or Query replace (remember adding Meta key enables Regex)

Without going into compatibility theory, regular expression allow defining strings by their structure, not just their content

The simplest regular expression is just normal characters, which only matches that exact sequence, nothing special

Regular expressions are extremely useful for programming in general, and the following is just a basic introduction:

? means the preceding character is optional, or in other words is repeated 0 or 1 times

“maths?” will match with both “math” and “maths”

+ means the preceding character can be repeated

“hey+” matches “heyyyy” and “hey” but not “he”

* means the preceding character can be repeated AND is optional

^ and ? mean beginning of line and end of line respectively

[…] will match with any of the characters in the brackets

“[abc]” matches “a” and “c”, but not “d” or “aa”
“[abc]*” will match “aa” though

[^…] matches anything not in the brackets

a “.” matches any character at all

“letter.” matches with “lettera” and “letterq” and “letter”

Adding a \ before one of the above special characters will treat it like a normal character to search for

\| is an or, treated like an XOR of the two expression.

There are many more, but you will need to discover those on your own (trust me it is worth doing)

Open up README.md and fix it so that the start of every sentence is capitalized. Try to do it with as few keys as possible or as fast as possible!

Go into columnar_transposition_cipher.java and try to improve its readability by adding a space to either side of operators (e.g. 1>2 becomes 1 > 2)

Directory Editor

Accessed with M-x dired

Once in dired Emacs bindings all take a different form, press h to access the help page

You can mark various files and folders for future commands with m, and for deletion with d

x will then delete files marked for deletion, and any other command will affect those marked with m

Dired can be turned into a write enabled buffer with C-x C-q (M-x dired-toggle-read-only)

This allows you to use all of the editing capacity of Emacs on directories instead of files!

Try navigating the files using dired. Then make a new copy of every file, and add a “.old” ending to the old ones

Using Linux commands within Emacs

Many common programming work flows involve compiling or running code on the command line

The most general tool Emacs offers by default is actually running the shell in Emacs directly

M-x shell opens up your default system shell within Emacs that can be used freely

There are also alternative functions for running shell commands individually such as shell-command (M-!)

Try running game_of_life.py if you have python3 installed (it requires a number as a parameter)

Emacs also supports debugging and compiling tools from within Emacs

M-x compile will offer you a choice of compile command (default: make -k), which can be re-invoked with M-x recompile

M-x gdb will allow you to run gbd for debugging directly within Emacs as well

Lisp execution is direction supported within Emacs buffers

C-x C-e Will print the result of a lisp expression to mini buffer (* 10 5)

Most other languages such as Python have plugins that enable similar IDE-like integration

Org mode actually lets you run code from most languages directly in the buffer, making it the best implementation of literate programming

mylist = [i**2 for i in range(1,10)]
return mylist #By default org mode treats the code block as a single function, but that can be changed
my $var = 1;
my $var2 = 12;
return $var + $var2;
(+ (* 5 5) (+ 192 17))

Tags

Emacs can scan source files to create a TAGS file, keeping track of variable names, definitions, etc.

This table can be used for navigating source code in a single file or in a project, as well as refactoring and more

To create a TAGS table you need either an external program (etags,ctags,global, and more) or an emacs plugin called ggtags which extends etags

This can be a little tricky to setup but is absolutely worth it! Look up Emacs ggtags for detailed instructions if you want to go that route.

Regardless of how you create the TAGS file (or GTAGS file in the case of ggtags), Emacs can make use of it.

You very likely have a tool like etags already installed if you are on Linux

To find other instances of the variable on your cursor use M-.

Tags tables will also be used for things like autocomplete if available.

In my experience, tools like ggtags are much nicer than default tags, we will discuss plugins in the next section

Basic ELisp and Customizing Emacs

Emacs Under the Hood

The core of Emacs is written in C, and many of the most basic functions (like C-f) come from C code

Pretty much everything else is written in Lisp, which can then call C functions as needed

Whenever Emacs starts up, it will run an initialization file called (by default) init.el

The easiest way to find and edit this file is with M-: (find-file user-init-file) RET

Structure of init.el

Open up the init.el file included to get an idea of what it looks like

Structured like normal programming language, each line runs one after the next

The init file will set relevant variables, enable plugins and modes, and define functions you can use

Basically all of these actions are done with one of a handful of lisp functions

Most Useful Functions for Customizing Emacs

All of these functions can be looked up with C-h f function-name , and any that aren’t C code and be edited directly from there (but please don’t)

Semicolon ; comments lines

setq: Called with (setq Symbol Variable) and it puts the value of Variable into Symbol

;Tell Projectile, a project manager, to use Ivy for autocompletes
(setq projectile-completion-system 'ivy)

global-set-key: allows you to globally reassign hotkeys: (global-set-key KEY ‘FUNCTION-NAME)

Note that when you use a name in Lisp, a single quote before it means use this functions name

Without the semicolon, it will assume your function is a variable, and try (and fail) to access it.

Example:

(global-set-key (kbd "C-f") 'backward-char) ;Ruin someones day

require: It will load a feature (i.e. plugin) from the default load path

Most use cases are simple, just download a plugin and add a require statement to init.el

For example, Ivy plugin is enabled with:

(require 'ivy)

add-hook: This will allow you to run a function whenever a given event or mode is loaded

The most common use case is enabling a minor mode from a plugin or otherwise only run for a given language

e.g. if I want structured haskell mode to turn on whenever I use haskell:

(add-hook 'haskell-mode-hook 'structured-haskell-mode)

Most of the time you will use this when following installation instructions for some plugin

lambda: Lisp is a functional language, so you can create anonymous one time use functions with lambda

This is most useful when you want to run a function with a parameter with something like add-hook, or run multiple functions

(add-hook 'haskell-mode-hook (lambda () (haskell-indentation-mode 0)) ;;Disable haskell indentation mode

Most of the time, passing a parameter of 0 to a function that enables a mode will disable it

The Package Manager

Emacs comes with a built in package manager to handle installing plugins

In order to actually download new plugins and keep them up to date, need an online repository

The most popular one, far and away, is MELPA, basically everything you will ever want is there

You need to tell Emacs to use MELPA in the init.el file, and its done for you

Most of the time, installing a plugin is as easy as M-x package-install RET package-name

A list of all packages on MELPA and options to install, uninstall, etc with M-x package-list-packages

Occasionally some packages will not be hosted on MELPA, and will have their own instructions

Copy the contents of the included init.el into your real init file. Find it with M-: (find-file user-init-file) RET

Install the package “solarized-theme”, “ivy” and “counsel” and “flx” and uncommon the lines in init corresponding to them

You may need to run M-x package-list-packages RET to refresh the package archives.

Change the init file so that line numers DON’T show up in org-mode (i.e. files ending in .org like this presentation)

;;One possible way to do that
(add-hook 'org-mode-hook (lambda () (linum-mode 0)))

Learning a New Programming Language is too Much Effort for an Editor

Don’t worry! Pretty much anything you will ever put in init.el will be from stackoverflow or similar

You will most likely start with a near barebones Emacs, and then build up from there.

A good way to get started customizing is googling something like “Emacs for c++”

Some Plugin Suggestions

Ivy

So useful I included it in the init.el that was distributed

Org Mode

Does basically everything organization related, and it is how this presentation was made

Also allows literate programming, which was shown in some other portions of the presentation

Can use it to create really good LaTeX documents without the pain of LaTeX, I do all reports this way

This mode is immensely powerful, and its features were barely touched on

EVIL Mode

Its a Vim compatibility layer, giving lots of Vim features including but not limited to Vim bindings

Company

This is a framework for text completion, and many other plugins rely on it

Projectile

This plugin keeps track of projects and lets you navigate and refactor files easily

ggtags

Mentioned earlier, it is basically a massive improvement on standard tags, but only for a few languages

Magit

The only frontend for git that is actually more efficient than the command line

Yasnippet

Lets you expand common statements like for loops and fill in the gaps

Avy

Lets you jump around a buffer in clever ways, kind of like searching but quicker

Many Many More

There are tons of language specific plugins and other fun stuff that can be easily found

Google “<language or setup you use> emacs ” for good examples

Alternatively, just browse through “package-list-packages” and see what’s available

There are a few niche packages that are not on MELPA, so installing them has more steps but is still easy.