This chapter talks about various topics relevant to adapting the behavior of Emacs in minor ways. See The Emacs Lisp Reference Manual for how to make more far-reaching changes.
All kinds of customization affect only the particular Emacs session that you do them in. They are completely lost when you kill the Emacs session, and have no effect on other Emacs sessions you may run at the same time or later. The only way an Emacs session can affect anything outside of it is by writing a file; in particular, the only way to make a customization `permanent' is to put something in your .emacs file or other appropriate file to do the customization in each session. See section The Init File, ~/.emacs.
Minor modes are optional features which you can turn on or off. For example, Auto Fill mode is a minor mode in which SPC breaks lines between words as you type. All the minor modes are independent of each other and of the selected major mode. Most minor modes say in the mode line when they are on; for example, Fill in the mode line means that Auto Fill mode is on.
Enabling or disabling some minor modes applies only to the current buffer; each buffer is independent of the other buffers. Therefore, you can enable the mode in particular buffers and disable it in others. The per-buffer minor modes include Auto Fill mode, Auto Save mode, Font-Lock mode, ISO Accents mode, Outline minor mode, Overwrite mode, and Binary Overwrite mode.
Font-Lock mode automatically highlights certain textual units found in programs, such as comments, strings, and function names being defined. This requires a window system that can display multiple fonts. See section Using Multiple Typefaces.
ISO Accents mode makes the characters `, ', ", ^, / and ~ combine with the following letter, to produce an accented letter in the ISO Latin-1 character set. See section European Character Set Display.
Outline minor mode provides the same facilities as the major mode called Outline mode; but since it is a minor mode instead, you can combine it with any major mode. See section Outline Mode.
Overwrite mode causes ordinary printing characters to replace existing text instead of shoving it to the right. For example, if point is in front of the B in FOOBAR, then in Overwrite mode typing a G changes it to FOOGAR, instead of producing it FOOGBAR as usual. Binary Overwrite mode is a variant of Overwrite mode for editing binary files; it treats newlines and tabs like other characters, so that they overwrite other characters and can be overwritten by them.
The following minor modes normally apply to all buffers at once. Since each is enabled or disabled by the value of a variable, you can set them differently for particular buffers, by explicitly making the corresponding variables local in those buffers. See section Local Variables.
Scroll Bar mode gives each window a scroll bar (see section Scroll Bars). Menu Bar mode gives each frame a menu bar (see section Menu Bars). Both of these modes are enabled by default when you use the X Window System.
In Transient Mark mode, every change in the buffer contents ``deactivates'' the mark, so that commands that operate on the region will get an error. This means you must either set the mark, or explicitly ``reactivate'' it, before each command that uses the region. The advantage of Transient Mark mode is that Emacs can display the region highlighted (currently only when using X). See section Setting the Mark.
For most minor modes, the command name is also the
name of a variable which directly controls the mode.
The mode is enabled whenever this variable's value is
These minor mode variables provide a good way for Lisp programs to turn minor modes on and off; they are also useful in a file's local variables list. But please think twice before setting minor modes with a local variables list, because most minor modes are matter of user preference---other users editing the same file might not want the same minor modes you prefer.
A variable is a Lisp symbol which has a value. The symbol's name is also called the name of the variable. A variable name can contain any characters that can appear in a file, but conventionally variable names consist of words separated by hyphens. A variable can have a documentation string which describes what kind of value it should have and how the value will be used.
Lisp allows any variable to have any kind of value,
but most variables that Emacs uses require a value of a certain type. Often the value
should always be a string, or should always be a
number. Sometimes we say that a certain feature is turned on if a variable is ``non-
Emacs uses many Lisp variables for internal record keeping, as any Lisp program must, but the most interesting variables for you are the ones that exist for the sake of customization. Emacs does not (usually) change the values of these variables; instead, you set the values, and thereby alter and control the behavior of certain Emacs commands. These variables are called options. Most options are documented in this manual, and appear in the Variable Index (see section Variable Index).
One example of a variable which is an option is
To examine the value of a single variable, use C-h
C-h v fill-column RET
displays something like this:
fill-column's value is 75
The most convenient way to set a specific option is with M-x set-variable. This reads the variable name with the minibuffer (with completion), and then reads a Lisp expression for the new value using the minibuffer a second time. For example,
M-x set-variable RET fill-column RET 75 RET
You can set any variable with a Lisp expression
using the function
(setq fill-column 75)
Setting variables, like all means of customizing Emacs except where otherwise stated, affects only the current Emacs session.
These two functions make it easy to display all the Emacs option variables, and to change some of them if you wish.
M-x list-options displays a list of all Emacs option variables, in an Emacs buffer named *List Options*. Each option is shown with its documentation and its current value. Here is what a portion of it might look like:
;; exec-path: ("." "/usr/local/bin" "/usr/ucb" "/bin" "/usr/bin" "/u2/emacs/etc") *List of directories to search programs to run in subprocesses. Each element is a string (directory name) or nil (try the default directory). ;; ;; fill-column: 75 *Column beyond which automatic line-wrapping should happen. Automatically becomes buffer-local when set in any fashion. ;;
M-x edit-options goes one step further and immediately selects the *List Options* buffer; this buffer uses the major mode Options mode, which provides commands that allow you to point at an option and change its value:
Any changes take effect immediately, and last until you exit from Emacs.
Most of the hooks in Emacs are normal hooks. These variables contain lists of functions to be called with no arguments. The reason most hooks are normal hooks is so that you can use them in a uniform way. Every variable in Emacs whose name ends in -hook is a normal hook.
Most major modes run hooks as the last step of initialization. This makes it easy for a
user to customize the behavior of the mode, by overriding the local variable
assignments already made by the mode. But hooks may also be used in other contexts. For
example, the hook
The recommended way to add a hook function to a normal hook is by calling
(add-hook 'text-mode-hook 'turn-on-auto-fill)
The next example shows how to use a hook to customize the indentation of C code. (People often have strong personal preferences for one format compared to another.) Here the hook function is an anonymous lambda expression.
(add-hook 'c-mode-hook (function (lambda () (setq c-indent-level 4 c-argdecl-indent 0 c-label-offset -4 c-continued-statement-indent 0 c-brace-offset 0 comment-column 40))))
(setq c++-mode-hook c-mode-hook)
It is best to design your hook functions so that the order in which they are executed does not matter. Any dependence on the order is ``asking for trouble.'' However, the order is predictable: the most recently added hook functions are executed first.
Almost any variable can be made local to a specific Emacs buffer. This means that its value in that buffer is independent of its value in other buffers. A few variables are always local in every buffer. Every other Emacs variable has a global value which is in effect in all buffers that have not made the variable local.
M-x make-local-variable reads the name of a variable and makes it local to the current buffer. Further changes in this buffer will not affect others, and further changes in the global value will not affect this buffer.
reads the name of a variable and changes the future
behavior of the variable so that it will become local automatically when it is set. More precisely, once a
variable has been marked in this way, the usual ways
of setting the variable automatically do
Major modes (see section Major Modes) always make
variables local to the buffer
before setting the variables. This is why changing major modes in one buffer has no effect on other buffers. Minor modes also
work by setting variables---normally, each minor mode has one controlling variable which is non-
Emacs contains a number of variables that are always per-buffer.
A few variables cannot be local to a buffer because they are always local to each display instead (See section Multiple Displays). If you try to make one of these variables buffer-local, you'll get an error message.
M-x kill-local-variable reads the name of a variable and makes it cease to be local to the current buffer. The global value of the variable henceforth is in effect in this buffer. Setting the major mode kills all the local variables of the buffer except for a few variables specially marked as permanent locals.
To set the global value of a variable, regardless of whether the variable has a local
value in the current buffer, you can use the Lisp
(setq-default fill-column 75)
Lisp programs can use
A file can specify local variable values for use when you edit the file with Emacs. Visiting the file checks for local variables specifications; it automatically makes these variables local to the buffer, and sets them to the values specified in the file.
-*- mode: modename; var: value; ... -*-
You can specify any number of variables/value pairs in this way, each pair with a colon
and semicolon as shown above.
;; -*-mode: Lisp; fill-column: 75; comment-column: 50; -*-
A local variables list goes near the end of the file, in the last page. (It is often best to put it on a page by itself.) The local variables list starts with a line containing the string Local Variables:, and ends with a line containing the string End:. In between come the variable names and values, one set per line, as variable: value. The values are not evaluated; they are used literally. If a file has both a local variables list and a -*- line, Emacs processes everything in the -*- line first, and everything in the local variables list afterward.
;;; Local Variables: *** ;;; mode:lisp *** ;;; comment-column:0 *** ;;; comment-start: ";;; " *** ;;; comment-end:"***" *** ;;; End: ***
As you see, each line starts with the prefix ;;; and each line ends with the suffix ***. Emacs recognizes these as the prefix and suffix based on the first line of the list, by finding them surrounding the magic string Local Variables:; then it automatically discards them from the other lines of the list.
The usual reason for using a prefix and/or suffix is to embed the local variables list in
a comment, so it won't confuse other programs that the
file is intended as input for. The example above is for a language where comment lines start with ;;; and end with ***;
the local values for
Two ``variable names'' have special meanings in a local variables list: a
value for the variable
You can use the
The start of the local variables list must be no more than 3000 characters from the end of the file, and must be in the last page if the file is divided into pages. Otherwise, Emacs will not notice it is there. The purpose of this rule is so that a stray Local Variables: not in the last page does not confuse Emacs, and so that visiting a long file that is all one page and has no local variables list need not take the time to search the whole file.
You may be tempted to try to turn on Auto Fill mode with a local variable list. That is a mistake. The choice of Auto Fill mode or not is a matter of individual taste, not a matter of the contents of particular files. If you want to use Auto Fill, set up major mode hooks with your .emacs file to turn it on (when appropriate) for you alone (see section The Init File, ~/.emacs). Don't try to use a local variable list that would impose your taste on everyone.
Use the command
A keyboard macro is a command defined by the user to stand for another sequence of keys. For example, if you discover that you are about to type C-n C-d forty times, you can speed your work by defining a keyboard macro to do C-n C-d and calling it with a repeat count of forty.
Keyboard macros differ from ordinary Emacs commands in that they are written in the Emacs command language rather than in Lisp. This makes it easier for the novice to write them, and makes them more convenient as temporary hacks. However, the Emacs command language is not powerful enough as a programming language to be useful for writing anything intelligent or general. For such things, Lisp must be used.
You define a keyboard macro while executing the commands which are the definition. Put differently, as you define a keyboard macro, the definition is being executed for the first time. This way, you can see what the effects of your commands are, so that you don't have to figure them out in your head. When you are finished, the keyboard macro is defined and also has been, in effect, executed once. You can then do the whole thing over again by invoking the macro.
To start defining a keyboard macro, type the C-x ( command (
C-x ( M-f foo C-x )
defines a macro to move forward a word and then insert foo.
The macro thus defined can be invoked again with the C-x e command (
If you wish to repeat an operation at regularly spaced places in the text, define a macro and include as part of the macro the commands to move to the next place you want to use it. For example, if you want to change each line, you should position point at the start of a line, and define a macro to change that line and leave point at the start of the next line. Then repeating the macro will operate on successive lines.
After you have terminated the definition of a keyboard macro, you can add to the end of its definition by typing C-u C-x (. This is equivalent to plain C-x ( followed by retyping the whole definition so far. As a consequence it re-executes the macro as previously defined.
You can use function keys in a keyboard macro, just like keyboard keys. You can even use mouse events, but be careful about that: when the macro replays the mouse event, it uses the original mouse position of that event, the position that the mouse had while you were defining the macro. The effect of this may be hard to predict. (Using the current mouse position would be even less predictable.)
One thing that doesn't always work well in a keyboard macro is the command C-M-c (
You can edit a keyboard macro already defined by typing C-x C-k (
If you wish to save a keyboard macro for longer than until you define the next one, you
must give it a name using M-x name-last-kbd-macro. This reads a name as an
argument using the minibuffer and defines that name to
execute the macro. The macro name is a Lisp symbol, and defining it in this way makes it a
valid command name for calling with M-x or
for binding a key to with
Once a macro has a command name, you can save its definition in a file. Then it can be used in another editing session. First, visit the file you want to save the definition in. Then use this command:
M-x insert-kbd-macro RET macroname RET
This inserts some Lisp code that, when executed later, will define the same macro with
the same definition it has now. (You need not understand Lisp code to do this, because
If you give
Using C-x q (
The valid responses when C-x q asks are SPC (or y), DEL
(or n), ESC (or q), C-l and C-r.
The answers are the same as in
These responses include SPC to continue, and DEL to skip the remainder of this repetition of the macro and start right away with the next repetition. ESC means to skip the remainder of this repetition and cancel further repetitions. C-l redraws the screen and asks you again for a character to say what to do.
C-r enters a recursive editing level, in which you can perform editing which is not part of the macro. When you exit the recursive edit using C-M-c, you are asked again how to continue with the keyboard macro. If you type a SPC at this time, the rest of the macro definition is executed. It is up to you to leave point and the text in a state such that the rest of the macro will do what you want.
C-u C-x q, which is C-x q with a numeric argument, performs a completely different function. It enters a recursive edit reading input from the keyboard, both when you type it during the definition of the macro, and when it is executed from the macro. During definition, the editing you do inside the recursive edit does not become part of the macro. During macro execution, the recursive edit gives you a chance to do some particularized editing on each repetition. See section Recursive Editing Levels.
This section describes key bindings which map keys to commands, and the keymaps which record key bindings. It also explains how to customize key bindings.
Recall that a command is a Lisp function whose definition provides for interactive use. Like every Lisp function, a command has a function name which usually consists of lower case letters and hyphens.
The bindings between key sequences and command functions are recorded in data structures called keymaps. Emacs has many of these, each used on particular occasions.
Recall that a key sequence (key, for short) is a sequence of input events that have a meaning as a unit. Input events include characters, function keys and mouse buttons---all the inputs that you can send to the computer with your terminal. A key sequence gets its meaning from its binding, which says what command it runs. The function of keymaps is to record these bindings.
The global keymap is the most important keymap because it is always in effect. The global keymap defines keys for Fundamental mode; most of these definitions are common to most or all major modes. Each major or minor mode can have its own keymap which overrides the global definitions of some keys.
For example, a self-inserting character such as g
is self-inserting because the global keymap binds it to the command
Meta characters work differently; Emacs translates each Meta character into a pair of characters starting with ESC. When you type the character M-a in a key sequence, Emacs replaces it with ESC a. A meta key comes in as a single input event, but becomes two events for purposes of key bindings. The reason for this is historical, and we might change it someday.
On many terminals, typing a function key actually sends the computer a sequence of characters; the precise details of the sequence depends on which function key and on the model of terminal you are using. (Often the sequence starts with ESC [.) If Emacs understands your terminal type properly, it recognizes the character sequences forming function keys wherever they occur in a key sequence (not just at the beginning). Thus, for most purposes, you can pretend the function keys reach Emacs directly and ignore their encoding as character sequences.
Mouse buttons also produce input events. These events come with other data---the window and position where you pressed or released the button, and a time stamp. But only the choice of button matters for key bindings; the other data matters only if a command looks at it. (Commands designed for mouse invocation usually do look at the other data.)
A keymap records definitions for single events. Interpreting a key sequence of multiple events involves a chain of keymaps. The first keymap gives a definition for the first event; this definition is another keymap, which is used to look up the second event in the sequence, and so on.
Key sequences can mix function keys and characters. For example, C-x SELECT makes sense. If you make SELECT a prefix key, then SELECT C-n makes sense. You can even mix mouse events with keyboard events, but we recommend against it, because such sequences are inconvenient to type in.
A prefix key such as C-x or ESC has its own keymap, which holds the definition for the event that immediately follows that prefix.
The definition of a prefix key is usually the keymap
to use for looking up the following event. The definition can also be a Lisp symbol whose
function definition is the following keymap; the effect
is the same, but it provides a command name for the
prefix key that can be used as a description of what the prefix key is for. Thus, the binding of C-x is the symbol
Some prefix keymaps are stored in variables with names:
So far we have explained the ins and outs of the global map. Major modes customize Emacs by providing their own key bindings in local keymaps. For example, C mode overrides TAB to make it indent the current line for C code. Portions of text in the buffer can specify their own keymaps to substitute for the keymap of the buffer's major mode.
The local keymaps for Lisp mode, C mode, and several
other major modes always exist even when not in use. These are kept in variables named
All minor mode keymaps are created in advance. There is no way to defer their creation until the first time the minor mode is enabled.
A local keymap can locally redefine a key as a prefix key by defining it as a prefix keymap. If the key is also defined globally as a prefix, then its local and global definitions (both keymaps) effectively combine: both of them are used to look up the event that follows the prefix key. Thus, if the mode's local keymap defines C-c as another keymap, and that keymap defines C-z as a command, this provides a local meaning for C-c C-z. This does not affect other sequences that start with C-c; if those sequences don't have their own local bindings, their global bindings remain in effect.
Another way to think of this is that Emacs handles a multi-event key sequence by looking in several keymaps, one by one, for a binding of the whole key sequence. First it checks the minor mode keymaps for minor modes that are enabled, then it checks the major mode's keymap, and then it checks the global keymap. This is not precisely how key lookup works, but it's good enough for understanding ordinary circumstances.
To change the local bindings of a major mode, you must change the mode's local keymap. Normally you must wait until the first time the mode is used, because most major modes don't create their keymaps until then. If you want to specify something in your ~/.emacs file to change a major mode's bindings, you must use the mode's mode hook to delay the change until the mode is first used.
For example, the command
(add-hook 'texinfo-mode-hook '(lambda () (define-key texinfo-mode-map "\C-cp" 'backward-paragraph) (define-key texinfo-mode-map "\C-cn" 'forward-paragraph) ))
See section Hooks.
The way to redefine an Emacs key is to change its entry in a keymap. You can change the global keymap, in which case the change is effective in all major modes (except those that have their own overriding local definitions for the same key). Or you can change the current buffer's local map, which affects all buffers using the same major mode.
For example, suppose you like to execute commands in a subshell within an Emacs buffer, instead of suspending Emacs and executing commands
in your login shell. Normally, C-z is bound to the function
M-x global-set-key RET C-z shell RET
Set key C-z to command:
You can redefine function keys and mouse events in the same way; just type the function key or click the mouse when it's time to specify the key to rebind.
You can rebind a key that contains more than one event in the same way. Emacs keeps reading the key to rebind until it is a complete key (that is, not a prefix key). Thus, if you type C-f for key, that's the end; the minibuffer is entered immediately to read cmd. But if you type C-x, another character is read; if that is 4, another character is read, and so on. For example,
The two-character keys consisting of C-c followed by a letter are reserved for user customizations. Lisp programs are not supposed to define these keys, so the bindings you make for them will be available in all major modes and will never get in the way of anything.
You can remove the global definition of a key with
If you have redefined (or undefined) a key and you subsequently wish to retract the change, undefining the key will not do the job---you need to redefine the key with its standard definition. To find the name of the standard definition of a key, go to a Fundamental mode buffer and use C-h c. The documentation of keys in this manual also lists their command names.
If you want to prevent yourself from invoking a command by mistake, it is better to disable the command than to undefine the key. A disabled command is less work to invoke when you really want to. See section Disabling Commands.
If you have a set of key bindings that you like to use all the time, you can specify them in your .emacs file by using their Lisp syntax.
The simplest method for doing this works for ASCII characters and Meta-modified ASCII characters only. This method uses a string to represent the key sequence you want to rebind.
For example, here's how to bind C-z to
(global-set-key "\C-z" 'shell)
This example uses a string constant containing one character, C-z. The single-quote before the command name,
Here is another example that binds a key sequence two characters long:
(global-set-key "\C-xl" 'make-symbolic-link)
When the key sequence includes function keys or mouse button events, or non-ASCII
characters such as
The way to write a vector in Emacs Lisp is with square brackets around the vector elements. Use spaces to separate the elements. If an element is a symbol, simply write the symbol's name---no other delimiters or punctuation are needed. If a vector element is a character, write it as a Lisp character constant: ? followed by the character as it would appear in a string.
Here are examples of using vectors to rebind C-= (a control character outside of ASCII), H-a (a Hyper character; ASCII doesn't have Hyper at all); f7 (a function key), and C-Mouse-1 (a keyboard-modified mouse button):
(global-set-key [?\C-=] 'make-symbolic-link) (global-set-key [?\H-a] 'make-symbolic-link) (global-set-key [f7] 'make-symbolic-link) (global-set-key [C-mouse-1] 'make-symbolic-link)
You can use a vector for the simple cases too. Here's how to rewrite the first two examples, above, to use vectors:
(global-set-key [?\C-z] 'shell)
(global-set-key [?\C-x ?l] 'make-symbolic-link)
Key sequences can contain function keys as well as ordinary characters. Just as Lisp characters (actually integers) represent keyboard characters, Lisp symbols represent function keys. If the function key has a word as its label, then that word is also the name of the corresponding Lisp symbol. Here are the conventional Lisp names for common function keys:
These names are conventional, but some systems (especially when using X windows) may use different names. To make certain what symbol is used for a given function key on your terminal, type C-h c followed by that key.
A key sequence which contains function key symbols (or anything but ASCII characters)
must be a vector rather than a string. The vector
syntax uses spaces between the elements, and square brackets around the whole vector.
Thus, to bind function key f1 to the command
(global-set-key [f1] 'rmail)
(global-set-key [right] 'forward-char)
This uses the Lisp syntax for a vector containing the symbol
See section Rebinding Keys in Your Init File, for more information about using vectors for rebinding.
You can use the modifier keys CTRL, META, HYPER, SUPER, ALT and SHIFT with function keys. To represent these modifiers, add the strings C-, M-, H-, s-, A- and S- at the front of the symbol name. Thus, here is how to make Hyper-Meta-RIGHT move forward a word:
(global-set-key [H-M-right] 'forward-word)
TAB, RET, BS, LFD, ESC and DEL started out as names for certain ASCII control characters, used so often that they have special keys of their own. Later, users found it convenient to distinguish in Emacs between these keys and the ``same'' control characters typed with the CTRL key.
Emacs 19 distinguishes these two kinds of input, when used with the X Window System. It treats the ``special'' keys as function
If you do not want to distinguish between (for example) TAB and C-i,
make just one binding, for the ASCII character TAB (octal code 011). If you do want
to distinguish, make one binding for this ASCII character, and another for the ``function key''
With an ordinary ASCII terminal, there is no way to distinguish between TAB and C-i (and likewise for other such pairs), because the terminal sends the same character in both cases.
Emacs uses Lisp symbols to designate mouse buttons, too. The ordinary mouse events in Emacs are click events; these happen when you press a button and release it without moving the mouse. You can also get drag events, when you move the mouse while holding the button down. Drag events happen when you finally let go of the button.
The symbols for basic click events are
The symbols for drag events are similar, but have the prefix drag- before
the word mouse. For example, dragging the first button generates a
You can also define bindings for events that occur when a mouse button is pressed down. These events start with down- instead of drag-. Such events are generated only if they have key bindings. When you get a button-down event, a corresponding click or drag event will always follow.
If you wish, you can distinguish single, double, and triple clicks. A double click
means clicking a mouse button twice in approximately the same place. The first click
generates an ordinary click event. The second click, if it comes soon enough, generates a
double-click event instead. The event type for a double click event starts with double-:
This means that you can give a special meaning to the second click at the same place, but it must act on the assumption that the ordinary single click definition has run when the first click was received.
This constrains what you can do with double clicks, but user interface designers say that this constraint ought to be followed in any case. A double click should do something similar to the single click, only ``more so''. The command for the double-click event should perform the extra work for the double click.
Emacs also supports triple-click events whose names start with triple-. Emacs does not distinguish quadruple clicks as event types; clicks beyond the third generate additional triple-click events. However, the full number of clicks is recorded in the event list, so you can distinguish if you really want to. We don't recommend distinct meanings for more than three clicks, but sometimes it is useful for subsequent clicks to cycle through the same set of three meanings, so that four clicks are equivalent to one click, five are equivalent to two, and six are equivalent to three.
Emacs also records multiple presses in drag and button-down events. For example, when you press a button twice, then move the mouse while holding the button, Emacs gets a double-drag- event. And at the moment when you press it down for the second time, Emacs gets a double-down- event (which is ignored, like all button-down events, if it has no binding).
The symbols for mouse events also indicate the status of the modifier keys, with the usual prefixes C-, M-, H-, s-, A- and S-. These always precede double- or triple-, which always precede drag- or down-.
A frame includes areas that don't show text from the buffer,
such as the mode line and the scroll bar. You can tell whether a mouse button comes from a
special area of the screen by means of dummy ``prefix keys.'' For example, if you click
the mouse in the mode line, you get the prefix key
(global-set-key [mode-line mouse-1] 'scroll-up)
Here is the complete list of these dummy prefix keys and their meanings:
You can put more than one mouse button in a key sequence, but it isn't usual to do so.
Disabling a command marks the command as requiring confirmation before it can be executed. The purpose of disabling a command is to prevent beginning users from executing it by accident and being confused.
An attempt to invoke a disabled command interactively in Emacs displays a window containing the command's name, its documentation, and some instructions on what to do immediately; then Emacs asks for input saying whether to execute the command as requested, enable it and execute it, or cancel. If you decide to enable the command, you are asked whether to do this permanently or just for the current session. Enabling permanently works by automatically editing your .emacs file.
(put 'delete-region 'disabled t)
You can make a command disabled either by editing the .emacs file directly or with the command M-x disable-command, which edits the .emacs file for you. Likewise, M-x enable-command edits .emacs to enable a command permanently. See section The Init File, ~/.emacs.
Whether a command is disabled is independent of what key is used to invoke it; disabling also applies if the command is invoked using M-x. Disabling a command has no effect on calling it as a function from Lisp programs.
Some keyboards do not make it convenient to send all the special characters that Emacs uses. The most common problem case is the DEL character. Some keyboards provide no convenient way to type this very important character---usually because they were designed to expect the character C-h to be used for deletion. On these keyboard, if you press the key normally used for deletion, Emacs handles the C-h as a prefix character and offers you a list of help options, which is not what you want.
You can work around this problem within Emacs by setting up keyboard translations to turn C-h into DEL and DEL into C-h, as follows:
;; Translate C-h to DEL. (keyboard-translate ?\C-h ?\C-?)
;; Translate DEL to C-h. (keyboard-translate ?\C-? ?\C-h)
Keyboard translations are not the same as key bindings in keymaps (see section Keymaps). Emacs contains numerous keymaps that apply in different situations, but there is only one set of keyboard translations, and it applies to every character that Emacs reads from the terminal. Keyboard translations take place at the lowest level of input processing; the keys that are looked up in keymaps contain the characters that result from keyboard translation.
Under X, the keyboard key named DELETE is a function key and is distinct from the ASCII character named DEL. See section Named ASCII Control Characters. Keyboard translations affect only ASCII character input, not function keys; thus, the above example used under X does not affect the DELETE key. However, the translation above isn't necessary under X, because Emacs can also distinguish between the BACKSPACE key and C-h; and it normally treats BACKSPACE as DEL.
For full information about how to use keyboard translations, see section 'Translating Input' in The Emacs Lisp Reference Manual.
All the Emacs commands which parse words or balance parentheses are controlled by the syntax table. The syntax table says which characters are opening delimiters, which are parts of words, which are string quotes, and so on. Each major mode has its own syntax table (though sometimes related major modes use the same one) which it installs in each buffer that uses that major mode. The syntax table installed in the current buffer is the one that all commands use, so we call it ``the'' syntax table. A syntax table is a Lisp object, a vector of length 256 whose elements are numbers.
To display a description of the contents of the current syntax table, type C-h s
For full information on the syntax table, see section 'Syntax Tables' in The Emacs Lisp Reference Manual.
When Emacs is started, it normally loads a Lisp program from the file .emacs in your home directory. We call this file your init file because it specifies how to initialize Emacs for you. You can use the command line switches -q and -u to tell Emacs whether to load an init file, and which one (see section Entering and Exiting Emacs).
There can also be a default init file, which is the library named default.el,
found via the standard search path for libraries. The Emacs distribution contains no such
library; your site may create one for local
customizations. If this library exists, it is loaded whenever you start Emacs (except when
you specify -q). But your init file, if any, is loaded first; if it sets
Your site may also have a site startup file; this is named site-start.el, if it exists. Emacs loads this library before it loads your init file. To inhibit loading of this library, use the option -no-site-file.
If you have a large amount of code in your .emacs file, you should move it
into another file such as ~/something.el, byte-compile it, and make
your .emacs file load it with
The .emacs file contains one or more Lisp function call expressions. Each of
these consists of a function name followed by arguments, all surrounded by parentheses.
The second argument to
Here are some examples of doing certain commonly desired things with Lisp expressions:
Each terminal type can have a Lisp library to be loaded into Emacs when it is run on
that type of terminal. For a terminal type named termtype, the library is
called term/termtype and it is found by searching the directories
The usual purpose of the terminal-specific library is to map the escape sequences used
by the terminal's function keys onto more meaningful names, using
When the terminal type contains a hyphen, only the part of the name before the first
hyphen is significant in choosing the library name. Thus, terminal types aaa-48
and aaa-30-rv both use the library term/aaa. The code in the library
The library's name is constructed by concatenating the value of the variable
Emacs runs the hook
Normally Emacs uses the environment variable
More precisely, Emacs first determines which user's init file to use. It gets the user
name from the environment variables
There are two ways of canceling commands which are not finished executing: quitting with C-g, and aborting with C-] or M-x top-level. Quitting cancels a partially typed command or one which is already running. Aborting exits a recursive editing level and cancels the command that invoked the recursive edit. (See section Recursive Editing Levels.)
Quitting with C-g is used for getting rid of a partially typed command, or a numeric argument that you don't want. It also stops a running command in the middle in a relatively safe way, so you can use it if you accidentally give a command which takes a long time. In particular, it is safe to quit out of killing; either your text will all still be in the buffer, or it will all be in the kill ring (or maybe both). Quitting an incremental search does special things documented under searching; in general, it may take two successive C-g characters to get out of a search (see section Incremental Search).
C-g works by setting the variable
If you quit with C-g a second time before the first C-g is recognized, you activate the ``emergency escape'' feature and return to the shell. See section Emergency Escape.
There may be times when you cannot quit. When Emacs is waiting for the operating system to do something, quitting is impossible unless special pains are taken for the particular system call within Emacs where the waiting occurs. We have done this for the system calls that users are likely to want to quit from, but it's possible you will find another. In one very common case---waiting for file input or output using NFS---Emacs itself knows how to quit, but most NFS implementations simply do not allow user programs to stop waiting for NFS when the NFS server is hung.
Aborting with C-] (
The command ESC ESC ESC
The command M-x top-level is equivalent to ``enough'' C-] commands to get you out of all the levels of recursive edits that you are in. C-] gets you out one level at a time, but M-x top-level goes out all levels at once. Both C-] and M-x top-level are like all other commands, and unlike C-g, in that they take effect only when Emacs is ready for a command. C-] is an ordinary key and has its meaning only because of its binding in the keymap. See section Recursive Editing Levels.
This section describes various conditions in which Emacs fails to work normally, and how to recognize them and correct them.
If you find that DEL enters Help like Control-h instead of deleting a character, your terminal is sending the wrong code for DEL. You can work around this problem by changing the keyboard translation table (see section Keyboard Translations).
Recursive editing levels are important and useful features of Emacs, but they can seem like malfunctions to the user who does not understand them.
If the mode line has square brackets [...] around the parentheses that contain the names of the major and minor modes, you have entered a recursive editing level. If you did not do this on purpose, or if you don't understand what that means, you should just get out of the recursive editing level. To do so, type M-x top-level. This is called getting back to top level. See section Recursive Editing Levels.
If the data on the screen looks wrong, the first thing to do is see whether the text is really wrong. Type C-l, to redisplay the entire screen. If the screen appears correct after this, the problem was entirely in the previous screen update. (Otherwise, see section Garbage in the Text.)
Display updating problems often result from an incorrect termcap entry for the terminal you are using. The file etc/TERMS in the Emacs distribution gives the fixes for known problems of this sort. INSTALL contains general advice for these problems in one of its sections. Very likely there is simply insufficient padding for certain display operations. To investigate the possibility that you have this sort of problem, try Emacs on another terminal made by a different manufacturer. If problems happen frequently on one kind of terminal but not another kind, it is likely to be a bad termcap entry, though it could also be due to a bug in Emacs that appears for terminals that have or that lack specific features.
If C-l shows that the text is wrong, try undoing the changes to it using C-x u until it gets back to a state you consider correct. Also try C-h l to find out what command you typed to produce the observed results.
If a large portion of text appears to be missing at the beginning or end of the buffer, check for the word Narrow in the mode line. If it appears, the text you don't see is probably still present, but temporarily off-limits. To make it accessible again, type C-x n w. See section Narrowing.
If Emacs spontaneously displays I-search: at the bottom of the screen, it means that the terminal is sending C-s and C-q according to the poorly designed xon/xoff ``flow control'' protocol.
If this happens to you, your best recourse is to put the terminal in a mode where it
will not use flow control, or give it so much padding that it will never send a C-s.
(One way to increase the amount of padding is to set the variable
If you don't succeed in turning off flow control, the next best thing is to tell Emacs
to cope with it. To do this, call the function
Typically there are particular terminal types with which you must use flow control. You
can conveniently ask for flow control on those terminal types only, using
(enable-flow-control-on "vt100" "h19")
When flow control is enabled, you must type C-\ to get the effect of a C-s, and type C-^ to get the effect of a C-q. (These aliases work by means of keyboard translations; see section Keyboard Translations.)
If you get the error message Virtual memory exceeded, save your modified buffers with C-x s. This method of saving them has the smallest need for additional memory. Emacs keeps a reserve of memory which it makes available when this error happens; that should be enough to enable C-x s to complete its work.
Once you have saved your modified buffers, you can exit this Emacs job and start another, or you can use M-x kill-some-buffers to free space in the current Emacs job. If you kill buffers containing a substantial amount of text, you can safely go on editing. Emacs refills its memory reserve automatically when it sees sufficient free space available, in case you run out of memory another time.
Because at times there have been bugs causing Emacs to loop without checking
When you resume Emacs after a suspension caused by multiple C-g, it asks two questions before going back to what it had been doing:
Auto-save? (y or n) Abort (and dump core)? (y or n)
Answer each one with y or n followed by RET.
Saying y to Abort (and dump core)? causes an illegal
instruction to be executed, dumping core. This is to enable a wizard to figure out why
Emacs was failing to quit in the first place. Execution does not continue after a core
dump. If you answer n, execution does continue. With luck, GNU Emacs will
If Emacs is not really hung, just slow, you may invoke the double C-g feature without really meaning to. Then just resume and answer n to both questions, and you will arrive at your former state. Presumably the quit you requested will happen soon.
If using Emacs (or something else) becomes terribly frustrating and none of the techniques described above solve the problem, Emacs can still help you.
First, if the Emacs you are using is not responding to commands, type C-g C-g to get out of it and then start a new one.
Second, type M-x doctor RET.
The doctor will help you feel better. Each time you say something to the doctor, you must end it by typing RET RET. This lets the doctor know you are finished.
Sometimes you will encounter a bug in Emacs. Although we cannot promise we can or will fix the bug, and we might not even agree that it is a bug, we want to hear about problems you encounter. Often we agree they are bugs and want to fix them.
To make it possible for us to fix a bug, you must report it. In order to do so effectively, you must know when and how to do it.
If Emacs executes an illegal instruction, or dies with an operating system error message that indicates a problem in the program (as opposed to something like ``disk full''), then it is certainly a bug.
If Emacs updates the display in a way that does not correspond to what is in the buffer, then it is certainly a bug. If a command seems to do the wrong thing but the problem corrects itself if you type C-l, it is a case of incorrect display updating.
Taking forever to complete a command can be a bug, but you must make certain that it was really Emacs's fault. Some commands simply take a long time. Type C-g and then C-h l to see whether the input Emacs received was what you intended to type; if the input was such that you know it should have been processed quickly, report a bug. If you don't know whether the command should take a long time, find out by looking in the manual or by asking for assistance.
If a command does the wrong thing, that is a bug. But be sure you know for certain what it ought to have done. If you aren't familiar with the command, or don't know for certain how the command is supposed to work, then it might actually be working right. Rather than jumping to conclusions, show the problem to someone who knows for certain.
Finally, a command's intended definition may not be best for editing with. This is a very important sort of problem, but it is also a matter of judgment. Also, it is easy to come to such a conclusion out of ignorance of some of the existing features. It is probably best not to complain about such a problem until you have checked the documentation in the usual ways, feel confident that you understand it, and know for certain that what you want is not available. If you are not sure what the command is supposed to do after a careful reading of the manual, check the index and glossary for any terms that may be unclear.
If after careful rereading of the manual you still do not understand what the command should do, that indicates a bug in the manual, which you should report. The manual's job is to make everything clear to people who are not Emacs experts---including you. It is just as important to report documentation bugs as program bugs.
When you decide that there is a bug, it is important to report it and to report it in a way which is useful. What is most useful is an exact description of what commands you type, starting with the shell command to run Emacs, until the problem happens.
The most important principle in reporting a bug is to report facts, not hypotheses or categorizations. It is always easier to report the facts, but people seem to prefer to strain to posit explanations and report them instead. If the explanations are based on guesses about how Emacs is implemented, they will be useless; we will have to try to figure out what the facts must have been to lead to such speculations. Sometimes this is impossible. But in any case, it is unnecessary work for us.
For example, suppose that you type C-x C-f /glorp/baz.ugh RET, visiting a file which (you know) happens to be rather large, and Emacs prints out I feel pretty today. The best way to report the bug is with a sentence like the preceding one, because it gives all the facts and nothing but the facts.
Do not assume that the problem is due to the size of the file and say, ``When I visit a large file, Emacs prints out I feel pretty today.'' This is what we mean by ``guessing explanations''. The problem is just as likely to be due to the fact that there is a z in the file name. If this is so, then when we got your report, we would try out the problem with some ``large file'', probably with no z in its name, and not find anything wrong. There is no way in the world that we could guess that we should try visiting a file with a z in its name.
Alternatively, the problem might be due to the fact that the file starts with exactly 25 spaces. For this reason, you should make sure that you inform us of the exact contents of any file that is needed to reproduce the bug. What if the problem only occurs when you have typed the C-x C-a command previously? This is why we ask you to give the exact sequence of characters you typed since starting the Emacs session.
You should not even say ``visit a file'' instead of C-x C-f unless you know that it makes no difference which visiting command is used. Similarly, rather than saying ``if I have three characters on the line,'' say ``after I type RET A B C RET C-p,'' if that is the way you entered the text.
The best way to send a bug report is to mail it electronically to the Emacs maintainers at bug-gnu-. (If you want to suggest a change as an improvement, use the same address.)
If you'd like to read the bug reports, you can find them on the newsgroup gnu.emacs.bug; keep in mind, however, that as a spectator you should not criticize anything about what you see there. The purpose of bug reports is to give information to the Emacs maintainers. Spectators are welcome only as long as they do not interfere with this. In particular, some bug reports contain large amounts of data; spectators should not complain about this.
Please do not post bug reports using netnews; mail is more reliable than netnews about reporting your correct address, which we may need in order to ask you for more information.
GNU Emacs Bugs Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA
We do not promise to fix the bug; but if the bug is serious, or ugly, or easy to fix, chances are we will want to.
To enable maintainers to investigate a bug, your report should include all these things:
Here are some things that are not necessary in a bug report:
If you would like to write bug fixes or improvements for GNU Emacs, that is very helpful. When you send your changes, please follow these guidelines to make it easy for the maintainers to use them. If you don't follow these guidelines, your information might still be useful, but using it will take extra work. Maintaining GNU Emacs is a lot of work in the best of circumstances, and we can't keep up unless you do your best to help.
If you need help installing, using or changing GNU Emacs, there are two ways to find it:
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