GiellaLT provides an infrastructure for rule-based language technology aimed at minority and indigenous languages, and streamlines building anything from keyboards to speech technology.
Emacs is a very good editor, available on all unix systems, also when working on a remote machine. The
To start emacs, write emacs filename, where filename is the name of the file you want to edit. Emacs will open the file you have requested. If you want to create a new file, then write the same command, and emacs will open with a blank page. In order to quit, press C-x C-c (where C-x means “hold down the ctrl key and press x”). Emacs will then ask you whether you want to save the file or not. If you suddenly are unable to type anything, and get strange messages on the screen, type C-g (interrupt)
The best short emacs reference is found in the emacs chapter of OReillys UNIX in a Nutshell. Other references may be found below.
C = ctrl, M = meta (either ESC or Alt (Linux) or ESC (Mac). Note that on Linux, the key following meta is pressed at the same time as the meta key whereas on Mac, it is pressed after the ESC key have been released.
Basic commands
Commands for searching in lexica
Moving around
Much of what follow is taken from a text written by Keith Waclena .
In the rest of this document I use the standard Emacs notation to describe keystrokes:
C-x :M-x :C-M-x :RET :C-m actually). This is the key to the right of the
letters, not the one in the lower right corner of the keyboard.SPC :ESC :C-[Every command has a long name, which you can look up in the
documentation, like kill-line, delete-backward-char, or
self-insert-command. These commands are bound to keystrokes for
convenient editing. We call such a pairing of keystroke and command a
key binding.
Prefix commands often group together commands that are somehow related.
The standard prefix commands are:
C-c :C-h :C-x :There’s one Emacs command that can be used to execute any other command
by typing it’s long name: M-x. When you type M-x Emacs prompts you
for the name of any command, and then executes it.
ESC PrefixThere’s one other prefix command that’s both very important and
completely redundant: the ESC prefix.
Not all keyboards provide a Meta key that sets the high order bit. On
a PC running Emacs natively, the ALT key is used for Meta. But when
using a PC to talk to a Unix box via some telecommunications program –
well, you guessed it – the ALT key may not work for this.
But if you have no Meta key, all is not lost. You just use the ESC
prefix. M-a becomes ESC a; C-M-f becomes ESC C-f (remember the
equivalence of C-M-f and M-C-f and this will make sense).
There’s only one trick: ESC is not a shift key. It’s actually an
ASCII character, not a key modifier. This means that you don’t try to
hold down ESC at the same time as the other key: use it as a prefix
character and type it separately and distinctly. If you lean on it it’s
likely to autorepeat (like any other key) and you’ll get very confused.
A true Meta is a wonderful thing for Emacs (it makes typing much
faster), but it is possible to use ESC for years with no trouble.
Emacs has three data structures that are intimately related, and very important to understand:
C-x C-f :find-file. This is the main command used to read a file into a
buffer for editing. When you execute this command, it prompts you
for the name of the file (with completion). Then it
checks to see if you’re already editing that file in some buffer; if
you are, it simply switches to that buffer and doesn’t actually read
in the file from disk again. If you’re not, a new buffer is created,
named for the file, and initialized with a copy of the file. In
either case the current window is switched to view this buffer.C-x C-s :save-buffer. This is the main command used to save a file, or,
more accurately, to write a copy of the current buffer out to the
disk, overwriting the buffer’s file, and handling backup versions.C-x s :save-some-buffers. Allows you to save all your buffers that are
visiting files, querying you for each one and offering several
options for each (save it, don’t save it, peek at it first then
maybe save it, etc).C-x b :switch-to-buffer. Prompts for a buffer name and switches the
buffer of the current window to that buffer. Doesn’t change your
window configuration. This command will also create a new empty
buffer if you type a new name; this new buffer will not be visiting
any file, no matter what you name it.C-x C-b :list-buffers. Pops up a new window which lists all your buffers,
giving for each the name, modified or not, size in bytes, major mode
and the file the buffer is visiting.C-v :scroll-up. The basic command to scroll forward (toward the end of
the file) one screenful. By default Emacs leaves you two lines of
context from the previous screen.M-v :scroll-down. Just like C-v, but scrolls backward.C-x o :other-window. Switch to another window, making it the active
window. Repeated invocation of this command moves through all the
windows, left to right and top to bottom, and then circles around
again. Under a windowing system, you can use the left mouse button
to switch windows.C-x 1 :delete-other-windows. Deletes all other windows except the current
one, making one window on the screen. Note that this in no way
deletes the buffers or files associated with the deleted windows.C-x 0 :delete-window. Deletes just the current window, resizing the
others appropriately.C-x 2 :split-window-vertically. Splits the current window in two,
vertically. This creates a new window, but not a new buffer: the
same buffer will now be viewed in the two windows. This allows you
to view two different parts of the same buffer simultaneously.C-x 3 :split-window-horizontally. Splits the current window in two,
horizontally. This creates a new window, but not a new buffer: the
same buffer will now be viewed in the two windows. This allows you
to view two different parts of the same buffer simultaneously.C-M-v :scroll-other-window. Just like C-v, but scrolls the other
window. If you have more than two windows, the other window is the
window that C-o would switch to.It’s probably more important to understand these fundamental Emacs concepts than it is to understand any of the actual editing commands. The editing commands are details: you can learn them easily on your own if you get the groundwork right.
To enter emacs, you just say:
emacs
when it comes up, you won’t be editing any file. You can then use the file commands to read in files for editing. Alternatively, you can fire up Emacs with an initial file (or files) by saying:
emacs newfile.txt
To exit emacs, use the command C-x C-c. It will offer to save all your
buffers and then exit.
You can also suspend Emacs (in the Unix sense of stopping it and
putting it in the background) with C-x C-z (which is bound to
suspend-emacs). How you restart it is up to your shell, but is
probably based on the fg command.
Once you’ve got Emacs running, you can type into it.
The emacs screen is completely devoted to the text of your file, except for one line near the bottom of the screen: the mode line. This line is informational: you can never move into it. It’s almost always in reverse video or otherwise highlighted. It displays important information (which may change), including:
% signs).*scratch* if
you’re not editing any file).The blank line below the mode line is the minibuffer. The minibuffer is used by Emacs to display messages, and also for input when Emacs is prompting you to type something (it may want you to type yes or no in answer to a question, the name of a file to be edited, the long name of a command, etc).
Emacs will occasionally print messages in the minibuffer of its own accord, seemingly unrelated to what you’re doing. The two most common messages are “Mark set” and “Garbage collecting…”. The former means that Emacs has set the mark for you as a result of your last command; automatic mark setting is a convenient feature of some commands; see The Mark and The Region. The latter means that Emacs’ lisp engine is reclaiming storage. You can just ignore it and keep typing, if you like: Emacs won’t lose your characters.
Emacs doesn’t break lines for you automatically, unless you ask it to. By default it lets lines be as long as you type them.
It may seem annoying to have to hit return at the end of long lines, but this is actually just the default for certain modes. The reason for this is that Emacs is a programmer’s editor, and any editor that will insert line breaks without your telling it to isn’t safe for editing code or data. In modes oriented towards text, Emacs does insert line breaks for you (Auto fill is such a mode)
Sometimes Emacs will do something that you don’t understand: it will prompt you for some information, or beep when you try to type, or something equally confusing. This just means that you’ve typed some command unwittingly (hitting a random function key is a good way to demonstrate this).
When this happens, you just need to type C-g, which interrupts what
Emacs is doing. This will get you out of any questions that Emacs may be
asking you, and it will abort a partially typed key sequence (say if you
typed C-x by mistake).
Because Emacs is fully recursive, you may occasionally need to type
C-g more than once, to back out of a recursive sequence of commands.
Also, if Emacs is really wedged (say, in a network connection to some
machine which is down), typing three C-g’s quickly is guaranteed to
abort whatever’s wedging you.
Emacs has extensive online help, most of which is available when you press ESC, and thereafter help.
ESC help a :command-apropos. Prompts for a keyword and then lists all the
commands with that keyword in their long name.ESC help k :describe-key. Prompts for a keystroke and describes the command
bound to that key, if any.ESC help i :info. Enters the Info hypertext documentation reader.ESC help m :describe-mode. Describes the current major mode and its particular
key bindings.ESC help p :finder-by-keyword. Runs an interactive subject-oriented browser of
Emacs packages.ESC help t :help-with-tutorial. Run the Emacs tutorial. This is very helpful
for beginners.Emacs has a builtin hypertext documentation reader, called
Info . To
run it, type ESC help i or M-x info RET. It has it’s own tutorial,
which you should run the first time through by typing h. The tutorial
assumes you understand about as much about Emacs as is covered in this
document.
One of the most important Emacs commands is
undo , invoked
with C-_ (control underbar). C-_ is a valid ASCII character, but
some keyboards don’t generate it, so you can also use C-x u – but
it’s more awkward to type, since it’s a two-character command.
The undo command allows you to undo your editing, back in time. It’s handy when you accidentally convert all of a huge file to uppercase, say, or delete a huge amount of text. One keystroke changes everything back to normal.
We say Emacs has infinite undo because, unlike some editors, you can undo a long chain of commands, not just one previous one, even undoing through saves. We say Emacs has redo because you can reverse direction while undoing, thereby undoing the undo.
Once you get used to this feature you’ll laugh at any editor that doesn’t have it (unless you’re forced to use it…). It’s very important to get comfortable with undo as soon as possible; I recommend reading the undo section of the manual carefully and practicing.
Emacs never modifies your file on disk until you tell it to, but it’s very careful about saving your work for you in a number of ways.
foo, the backup will be called foo~ (note
the squiggle). Although it is off by default, Emacs will keep any
number of previous versions for you, named foo.~1~, foo.~2~,
etc. You can decide how many versions are to be kept. (But Unix
provides more powerful tools for managing multiple versions of
files.)foo is called #foo#. If Emacs
(or the system) were to crash before you could save your edits, you
can recover almost all of it from this file. Auto-saving happens (by
default) every 300 characters, or when a system error is
encountered.TAB.Many Emacs commands take arguments , exactly the way a procedure or function takes arguments in a programming language. Most commands prompt you for their arguments: e.g., a command to read in a file will prompt you for the filename.
There’s one kind of argument that’s so commonly accepted that there’s a
special way to provide it: numeric arguments. Many commands will
interpret a numeric argument as a request to repeat that many times. For
example, the delete-char command (bound to C-d), which normally
deletes one character to the right of the cursor, will delete N
characters if given a numeric argument of N. It works with
self-inserting commands too: try giving a numeric argument to a printing
character, like a hyphen.
To give a command a numeric argument of, say, 12, type C-u 12 before
typing the command. If you type slowly, you’ll see:
C-u 1 2-
in the echo area. Then type C-d and you’ll have given delete-char an
argument of 12. You can type any number of digits after C-u. A leading
hyphen makes a negative argument; a lone hyphen is the same as an
argument of -1. If you begin typing a numeric argument and change your
mind, you can of course type C-g to abort it.
Since one often isn’t interested in precisely how many times a command
is repeated, there’s a shorthand way to get numeric arguments of varying
magnitudes. C-u by itself, without any subsequent digits, is equal to
a numeric argument of 4. Another C-u multiplies that by 4 more, giving
a numeric argument of 16. Another C-u multiplies that by 4 more,
giving a numeric argument of 64, etc. For this reason C-u is called
the universal-argument.
Note that commands aren’t required to interpret numeric arguments as specifying repetitions. It depends on what’s appropriate: some commands ignore numeric arguments, some interpret them as Boolean (the presence of numeric argument – any numeric argument – as opposed to its absence), etc. Read the documentation for a command before trying it.
Sometimes one needs to insert control characters into a file. But how
can you insert an ESC, say, when it’s used as a prefix command? The
answer is to use the command
quoted-insert
, which is bound to C-q. C-q acts like a prefix command, in that
when you type it it waits for you to type another character. But this
next character is then inserted into the buffer, rather than being
executed as a command. So C-q ESC inserts an Escape.
C-q can also be used to insert characters by typing C-q followed by
their ASCII code as three octal digits.
Some commands that are especially confusing for novices are disabled by default. When a command is disabled, invoking it subjects you to a brief dialog, popping up a window displaying the documentation for the command, and giving you three choices:
You’re very likely to encounter one particular disabled command: M-ESC
(aka ESC ESC), because it’s very easy to type two escapes in a row
when using the Escape prefix.
One of the main things one does in an editor is move around, in order to apply editing commands. Emacs provides many motion commands, which are arranged around textual objects: for each textual object, there is typically a motion command that moves forward over such an object and backward over it (or you can think of this as moving to the beginning and to the end).
All these motion commands take numeric arguments as repetitions.
The most basic textual object is the character. Emacs understand many other objects, sometimes depending on what mode you’re in (a C function textual object probably doesn’t make much sense if you’re not editing C source code).
The exact definition of what makes up a given textual object is often customizable, but more importantly varies slightly from mode to mode. The characters that make up a word in Text Mode may not be exactly the same as those that make up a word in C Mode for example. (E.g., underbars are considered word constituents in C Mode, because they are legal in identifier names, but they aren’t considered word constituents in Text Mode.) This is extremely useful, because it means that you can use the same motion commands and yet have them automatically customized for different types of text.
C-f :forward-char. Moves forward (to the right) over a character.C-b :backward-char. Moves backward (to the left) over a character.The f for forward and b for backward mnemonic will reoccur.
M-f :forward-word. Moves forward over a word.M-b :backward-word. Moves backward over a word.Note the f/b mnemonic. Also, as another mnemonic, note that M-f is
like a “bigger” version of C-f.
C-n :next-line. Moves down to the next line.C-p :previous-line. Moves up to the previous line.When moving by lines, the cursor tries to stay in the same column, but if the new line is too short, it will be at the end of the line instead. This is very important: Emacs doesn’t insert spaces at the ends of lines (end of line is unambiguous).
C-a :beginning-of-line. Moves to the beginning of the current line.C-e :end-of-line. Moves to the end of the current line.E for end, A for the beginning of the alphabet.
M-a :backward-sentence. Moves to the beginning of the current sentence.M-e :forward-sentence. Moves to the end of the current sentence.Note the mnemonic relation between C-a / M-a and C-e / M-e.
M-{ :backward-paragraph. Move to the beginning of the current
paragraph.M-} :forward-paragraph. Move to the end of the current paragraph.C-x [ :backward-page. Moves to the beginning of the current page.C-x ] :forward-page. Moves to the end of the current page.Pages are separated by formfeed characters (C-l) in most modes.
M-< :beginning-of-buffer. Moves to the beginning of the buffer.M-> :end-of-buffer. Moves to the end of the buffer.An S-expression (sexp for short) is the name for balanced parentheses (and the text they enclose) in Lisp. In Emacs, this useful notion is available in most modes; it’s especially useful for editing programming languages. The characters that Emacs recognizes as parens are usually regular parentheses (aka round brackets), square brackets, and braces (aka curly brackets), but it depends on the mode (for some languages, angle brackets may act as parens).
But sexps are more than just balanced parens: they’re defined recursively. A word that doesn’t contain any parens also counts as a sexp. In most programming language modes, quoted strings are sexps (using either single or double quotes, depending on the syntax of the language). The sexp commands move in terms of all these units.
These commands may seem confusing at first, but for editing most programming languages they’re fantastic. Not only do they move you around quickly and accurately, but they help spot syntax errors while you’re editing, because they’ll generate an error if your parens or quotes are unbalanced.
C-M-b :backward-sexp. Moves backward over the next sexp. If your cursor
is just to the right of a left paren, C-M-b will beep, because
there’s no sexp to the left to move over: you have to move up.C-M-f :forward-sexp. Moves forward over the next sexp. Same deal if your
cursor is just to the left of a right paren.C-M-u :backward-up-list. Move backward up one level of parens. In other
words, move to the left paren of the parens containing the cursor,
skipping balanced sexps.C-M-d :down-list. Move down one level of parens. In other words, move to
the right of the next left paren, skipping balanced sexps. E.g., if
your cursor is sitting on the return type of a C function
declaration, C-M-d moves to the inside of the formal parameter
list.Since functions are such an important unit of text in programming languages, whether they’re called functions, subroutines, procedures, procs, defuns or whatever, Emacs has commands to move over them. Like the sexp commands, these commands work appropriately in most programming language modes. Emacs calls this generic notion of function or procedure defun, again after Lisp.
C-M-a :beginning-of-defun. Move to the beginning of the current defun.C-M-e :end-of-defun. Move to the end of the current defun.Note the mnemonic analogy with lines and sentences.
Emacs’ deletion commands are also based on the textual objects above. But first, a terminological distinction: Deletion means to remove text from the buffer without saving it; most deletion commands operate on small amounts of text. Killing means to save the removed text, so that it can be yanked back later someplace else. So, “Deletion” is permanent, “Killing” is deletion that can be undone, and “yanking” is the emacs term for paste.
Killed text is saved on what is called the kill ring. The kill ring
holds the last N kills, where N is 30 by default, but you can change
it to anything you like by changing the value of the variable
kill-ring-max. The kill ring acts like a fifo when you’re killing
things (after the 30th kill, kill number one is gone), but like a ring
when you’re yanking things back (you can yank around the ring
circularly). kill-ring-max doesn’t apply to the amount of text (in
bytes) that can be saved in the kill ring (there’s no limit), only to
the number of distinct kills.
C-d :delete-char. Deletes the character to the right of (under, if the
cursor is a block that covers a character) the cursor.DEL :delete-backward-char. Deletes the character to the left of the
cursor.M-d :kill-word. Kills to the end of the word to the right of the cursor
(forward).M-DEL :backward-kill-word. Kills to the beginning of the word to the left
of the cursor (backward).C-k :kill-line. Kills to the end of the current line, not including the
newline. Thus, if you’re at the beginning of a line it takes two
C-k’s to kill the whole line and close up the whitespace.C-u 0 C-k :kill-line. Kills to the beginning of the current line, not
including the newline.You might think that C-u -1 C-k would be used to kill to the beginning
of the line, and it does, but it includes the newline before the line as
well.
M-k :kill-sentence. Kills to the end of the current sentence, including
any newline within the sentence.C-u -1 M-k :kill-sentence. Kills to the beginning of the current sentence,
including any newlines within the sentence.The commands forward-kill-paragraph and backward-kill-paragraph
exist, but are not bound to any keys by default.
C-M-k :kill-sexp. Kills the sexp after the cursor.C-u -1 C-M-k :kill-sexp. Kills the sexp before the cursor.The command backward-kill-sexp exists, but is not bound to any key by
default.
If you kill several times in a row, with any combination of kill
commands, but without any non-kill commands in between, these kills
are appended together in one entry on the kill ring. For example you can
kill a block of text as several lines by saying C-u 6 C-k, which kills
(as one kill) 6 lines.
Once you’ve killed some text, how do you get it back? You can yank back
the most recently killed text with C-y (yank). Since Emacs has only
one kill ring (as opposed to one per buffer), you can kill in one
buffer, switch to another and yank the text there.
To get back previous kills, you move around the kill ring. Start with
C-y to get the most recent kill, and then use M-y to move to the
previous spot in the kill ring by replacing the just-yanked text with
the previous kill. Subsequent M-y’s move around the ring, each time
replacing the yanked text. When you reach the text you you’re interested
in, just stop. Any other command (a motion command, self-insert,
anything) breaks the cycling of the kill ring, and the next C-y yanks
the most recent kill again.
Emacs has no need for special commands to copy or move text; you’ve already learned them! To move text, just kill it and yank it back elsewhere. To copy text, kill it, yank it back immediately (so it’s as if you haven’t killed it, except it’s now in the kill ring), move elsewhere and yank it back again. For commands to copy and move arbitrary regions of text, as opposed to textual objects, see The Mark and The Region.
Emacs has a variety of unusual and extremely powerful search and replace
commands. The most important one is called incremental search. This is
what the command C-s, does: it searches incrementally, one character
at a time, as you type the search string. This means that Emacs can
often find what you’re looking for before you have to type the whole
thing. To stop searching, you can either hit RET or type any other
Emacs command (which will both stop the search and execute the command).
You can search for the next match at any point by typing another C-s
at any point; you can reverse the search (search backwards) by typing
C-r; and you can use DEL to delete and change what you’re searching
for.
C-r, works the same way, but searches backward. (Use C-r to search
for the next match and C-s to reverse the search.)
Another possibility is word search, which lets you search for a
sequence of one or more words, regardless of how they’re separated (e.g,
by any number and combination of newlines and whitespace). To invoke
word search, type C-s RET C-w word word word RET.
Emacs can also search incrementally (or not) by regular expressions. The
command is C-u-s, and it understands regular
expressions.
Emacs’ most important command for replacing text is called
query-replace (bound to M-%, type ESC, and thereafter %).
This command prompts you for the text to replace, and the text to
replace it with, and then searches and replaces within the current
buffer. query-replace is interactive: at each match, you are prompted
to decide what to do; you have the following options:
SPC :DEL :RET :query-replace without performing this replacement.ESC :RET.. :query-replace.! :There are many more subcommands, but they require more Emacs expertise to understand them.
There are also more replacement commands you should look into, including
replace-string (simple unconditional replacement), replace-regexp
and query-replace-regexp (which use regular expressions), and
tags-query-replace, which replaces all identifiers in a collection of
source code files.
query-replace-regexp is very important to us. The shortest way to
type it is ESC que TAB - TAB. If you e.g. want to add the text K
; to the end of each line of the rest of the file, type **ESC que TAB
query-replace and the other replacement commands are, by default,
smart about case. For example, if you’re replacing foo with bar and
find Foo, Emacs replaces it with Bar; if you find FOO, Emacs
replaces it with BAR, etc.
Emacs can manipulate arbitrary chunks of text as well as distinct textual objects. The way this is done is to define a region of text; many commands will operate on this region. this is what you do with the mouse in ordinary word processors.
The region is the text between point and mark. Point is actually the
Emacs term for what we’ve been calling the cursor up to now. The mark,
on the other hand, is set with a special command C-SPACEBAR
(mellomromstasten, välilyönti) (set-mark-command). This sets the mark
exactly where point is, but now you can move point elsewhere and you
have: the region.
The region is the same regardless of whether point comes first in the buffer or mark does; it makes no difference, just do what’s convenient.
Many commands that move point a significant distance (like M-< and
C-s, for example) leave the mark set at the spot they moved from.
You’ll see “Mark set” in the echo area when this happens.
When using Emacs under a windowing system like X, the mouse can be used to sweep out the region, but many Emacsers find it faster to keep their hands on the keyboard and use the familiar motion commands.
So now you know how to define the region: what can you do with it?
C-x C-x :exchange-point-and-mark. Swaps mark and point. Repeated rapid
execution of this command makes it easy to see the extent of the
region.C-w :kill-region. Kills the region. It goes on the kill ring, of
course.M-w :kill-ring-save. Saves the region to the kill ring without removing
it from the buffer. This is exactly equivalent to typing C-w C-y.C-x C-i :indent-rigidly. Rigidly indents the region by as many characters
(columns) as you provide as a numeric argument (default is 1
column).C-x C-l :downcase-region. Convert the entire region to lowercase. This
command is disabled by default.C-x C-u :upcase-region. Convert the entire region to uppercase. This
command is disabled by default.M-x fill-region :fill-region. Fills, i.e., justifies with a ragged right margin,
all the paragraphs within the region.There are many, many more.
The main way Emacs customizes commands for different kinds of text is
through major and minor modes. Every buffer has a major mode, and may
have zero or more minor modes. Sometimes Emacs chooses a major mode for
you automatically, typically based on a file extension (e.g., files
ending in .c will automatically be in C Mode; files ending in .tcl
will automatically be in Tcl Mode). But you can always set the mode
explicitly.
Fundamental Mode :Text Mode :HTML helper mode :There are many other major modes, some very specialized (e.g., modes for editing sending email, reading Usenet news, browsing directories, browsing the World Wide Web, etc).
ISO Latin characters :
C-q followed by the octal code of the character. For
example, C-q 341 RET gives the lower case a with acute (á).M-x load-library and respond to prompt with iso-insert. Then
use commands M-x insert-A-acute for inserting capital A with
acute (á).UTF-8 characters :
un-defineM-x insert-ucs-character and
giving the character’s unicode number.The GNU Emacs FAQ is very well done; I recommend it highly.
Don’t forget that the complete text of the GNU Emacs Manual is available via Info, Emacs’ hypertext documentation reader.
Only a selection of some of the Emacs-related Usenet newsgroups.