Info file elisp, produced by Makeinfo, -*- Text -*- from input file
elisp.texi.
This file documents GNU Emacs Lisp.
This is edition 1.03 of the GNU Emacs Lisp Reference Manual, for
Emacs Version 18.
Published by the Free Software Foundation, 675 Massachusetts
Avenue, Cambridge, MA 02139 USA
Copyright (C) 1990 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Foundation.
This section describes how to write the `interactive' form that
makes a Lisp function an interactively-callable command.
* Special Form: interactive ARG-DESCRIPTOR
This special form declares that the function in which it appears
is a command, and that it may therefore be called interactively
(via `M-x' or by entering a key sequence bound to it). The
argument ARG-DESCRIPTOR declares the way the arguments to the
command are to be computed when the command is called
interactively.
A command may be called from Lisp programs like any other
function, but then the arguments are supplied by the caller and
ARG-DESCRIPTOR has no effect.
The `interactive' form has its effect because the command loop
(actually, its subroutine `call-interactively') scans through
the function definition looking for it, before calling the
function. Once the function is called, all its body forms
including the `interactive' form are executed, but at this time
`interactive' simply returns `nil' without even evaluating its
argument.
There are three possibilities for the argument ARG-DESCRIPTOR:
* It may be omitted or `nil'; then the command is called with no
arguments. This leads quickly to an error if the command
requires one or more arguments.
* It may be a Lisp expression that is not a string; then it should
be a form that is evaluated to get a list of arguments to pass
to the command.
* It may be a string; then its contents should consist of a code
character followed by a prompt (if required for that code
character). The prompt ends either with the end of the string
or with a newline. Here is a simple example:
(interactive "bFrobnicate buffer: ")
The code letter `b' says to read the name of an existing buffer,
with completion. The buffer name will be the sole argument
passed to the command. The rest of the string is a prompt.
If there is a newline character in the string, it terminates the
prompt. If the string does not end there, then the rest of the
string should contain another code character and prompt,
specifying another argument. Any number of arguments may be
specified in this way.
If the first character in the string is `*', then an error is
signaled if the buffer is read-only. Otherwise, the following
character is the first code character.
Code Characters for `interactive'
---------------------------------
The code character descriptions below contain a number of key
words, defined here as follows:
Completion
Provide completion. TAB, SPC, and RET perform name completion
because the argument is read using `completing-read' (*note
Completion::.). `?' displays a list of possible completions.
Existing
Require the name of an existing object. An invalid name is not
accepted; the commands to exit the minibuffer do not exit if the
current input is not valid.
Default
A default value of some sort is used if the user enters no text
in the minibuffer. The default depends on the code character.
Prompt
A prompt immediately follows the code character. The prompt
ends either with the end of the string or with a newline.
No I/O
This code letter computes an argument without reading any input.
Therefore, it does not use a prompt string, and any prompt
string you supply is ignored.
Here are the code character descriptions for use with `interactive':
`a'
A function name (i.e., a symbol which is `fboundp'). Existing,
Completion, Prompt.
`b'
The name of an existing buffer. By default, uses the name of
the current buffer (*note Buffers::.). Existing, Completion,
Default, Prompt.
`B'
A buffer name. The buffer need not exist. By default, uses the
name of a recently used buffer other than the current buffer.
Completion, Prompt.
`c'
A character. The cursor does not move into the echo area.
Prompt.
`C'
A command name (i.e., a symbol satisfying `commandp').
Existing, Completion, Prompt.
`d'
The position of point as a number (*note Point::.). No I/O.
`D'
A directory name. The default is the current default directory
of the current buffer, `default-directory' (*note System
Environment::.). Existing, Completion, Default, Prompt.
`f'
A file name of an existing file (*note File Names::.). The
default directory is `default-directory'. Existing, Completion,
Default, Prompt.
`F'
A file name. The file need not exist. Completion, Default,
Prompt.
`k'
A key sequence (*note Keymap Terms::.). This keeps reading
characters until a command (or undefined command) is found in
the current key maps. The key sequence argument is represented
as a string. The cursor does not move into the echo area.
Prompt.
This kind of input is used by commands such as `describe-key'
and `global-set-key'.
`m'
The position of the mark as a number. No I/O.
`n'
A number read with the minibuffer. If the input is not a
number, the user is asked to try again. The prefix argument, if
any, is not used. Prompt.
`N'
The raw prefix argument. If the prefix argument is `nil', then
a number is read as with `n'. Requires a number. Prompt.
`p'
The numeric prefix argument. (Note that this `p' is lower
case.) No I/O.
`P'
The raw prefix argument. (Note that this `P' is upper case.)
*Note Prefix Command Arguments::. No I/O.
`r'
Point and the mark, as two numeric arguments, smallest first.
This is the only code letter that specifies two successive
arguments rather than one. No I/O.
`s'
Arbitrary text, read in the minibuffer and returned as a string
(*note Text from Minibuffer::.). Terminate the input with
either LFD or RET. (`C-q' may be used to include either of
these characters in the input.) Prompt.
`S'
An interned symbol whose name is read in the minibuffer. Any
whitespace character terminates the input. (Use `C-q' to
include whitespace in the string.) Other characters that
normally terminate a symbol (e.g., parentheses and brackets) do
not do so here. Prompt.
`v'
A variable declared to be a user option (i.e., satisfying
`user-variable-p'). *Note High-Level Completion::. Existing,
Completion, Prompt.
`x'
A Lisp object specified in printed representation, terminated
with a LFD or RET. The object is not evaluated. *Note Object
from Minibuffer::. Prompt.
`X'
A Lisp form is read as with `x', but then evaluated so that its
value becomes the argument for the command. Prompt.
Examples of Using `interactive'
-------------------------------
Here are some examples of `interactive':
(defun foo1 () ; `foo1' takes no arguments,
(interactive) ; just moves forward two words.
(forward-word 2))
=> foo1
(defun foo2 (n) ; `foo2' takes one argument,
(interactive "p") ; which is the numeric prefix.
(forward-word (* 2 n)))
=> foo2
(defun foo3 (n) ; `foo3' takes one argument,
(interactive "nCount:") ; which is read with the Minibuffer.
(forward-word (* 2 n)))
=> foo3
(defun three-b (b1 b2 b3)
"Select three existing buffers (prompting for them in
the Minibuffer). Put them into three windows, selecting the
last one."
(interactive "bBuffer1:\nbBuffer2:\nbBuffer3:")
(delete-other-windows)
(split-window (selected-window) 8)
(switch-to-buffer b1)
(other-window 1)
(split-window (selected-window) 8)
(switch-to-buffer b2)
(other-window 1)
(switch-to-buffer b3))
=> three-b
(three-b "*scratch*" "declarations.texi" "*mail*")
=> nil
After the command loop has translated a key sequence into a
definition, it invokes that definition using the function
`command-execute'. If the definition is a function that is a
command, `command-execute' calls `call-interactively', which reads
the arguments and calls the command. You can also call these
functions yourself.
* Function: commandp OBJECT
Returns `t' if OBJECT is suitable for calling interactively;
that is, if OBJECT is a command. Otherwise, returns `nil'.
The interactively callable objects include strings (treated as
keyboard macros), lambda expressions that contain a top-level
call to `interactive', autoload objects that are declared as
interactive (non-`nil' fourth argument to `autoload'), and some
of the primitive functions.
A symbol is `commandp' if its function definition is `commandp'.
Keys and keymaps are not commands. Rather, they are used to
look up commands (*note Keymaps::.).
See `documentation' in *Note Accessing Documentation::, for a
realistic example of using `commandp'.
* Function: call-interactively COMMAND &optional RECORD-FLAG
This function calls the interactively callable function COMMAND,
reading arguments according to its interactive calling
specifications. An error is signaled if COMMAND cannot be
called interactively (i.e., it is not a command). Note that
strings are not accepted, even though they are considered
commands.
If RECORD-FLAG is non-`nil', then this command and its arguments
are unconditionally added to the list `command-history'.
Otherwise, the command is added only if it uses the minibuffer
to read an argument. *Note Command History::.
* Function: command-execute COMMAND &optional RECORD-FLAG
This function executes COMMAND as an editing command. The
argument COMMAND must satisfy the `commandp' predicate; i.e., it
must be an interactively callable function or a string.
A string as COMMAND is executed with `execute-kbd-macro'. A
function is passed to `call-interactively', along with the
optional RECORD-FLAG.
A symbol is handled by using its function definition in its
place. A symbol with an `autoload' definition counts as a
command if it was declared to stand for an interactively
callable function. Such a definition is handled by loading the
specified library and then rechecking the definition of the
symbol.
* Command: execute-extended-command PREFIX-ARGUMENT
This primitive function reads a command name from the minibuffer
using `completing-read' (*note Completion::.). Then it uses
`command-execute' to call the specified command. Whatever that
command returns becomes the value of `execute-extended-command'.
If the command asks for a prefix argument, the value
PREFIX-ARGUMENT is supplied. If `execute-extended-command' is
called interactively, the current raw prefix argument is used
for PREFIX-ARGUMENT, and thus passed on to whatever command is
run.
`execute-extended-command' is the normal definition of `M-x', so
it uses the string `M-x ' as a prompt. (It would be better to
take the prompt from the characters used to invoke
`execute-extended-command', but that is painful to implement.)
A description of the value of the prefix argument, if any, also
becomes part of the prompt.
(execute-extended-command 1)
---------- Buffer: Minibuffer ----------
M-x forward-word RET
---------- Buffer: Minibuffer ----------
=> t
* Function: interactive-p
This function returns `t' if the containing function (the one
that called `interactive-p') was called interactively, with
`call-interactively'. (It makes no difference whether
`call-interactively' was called from Lisp or directly from the
editor command loop.) Note that if the containing function was
called by Lisp evaluation (or with `apply' or `funcall'), then
it was not called interactively.
The usual application of `interactive-p' is for deciding whether
to print an informative message. As a special exception,
`interactive-p' returns `nil' whenever a keyboard macro is being
run. This is to suppress the informative messages and speed
execution of the macro.
Information from the Command Loop
=================================
The editor command loop sets several Lisp variables to keep status
records for itself and for commands that are run.
* Variable: last-command
This variable records the name of the previous command executed
by the command loop (the one before the current command).
Normally the value is a symbol with a function definition, but
this is not guaranteed.
The value is set by copying the value of `this-command' when a
command returns to the command loop, except when the command
specifies a prefix argument for the following command.
* Variable: this-command
This variable records the name of the command now being executed
by editor command loop. Like `last-command', it is normally a
symbol with a function definition.
This variable is set by the command loop just before the command
is run, and its value is copied into `last-command' when the
command finishes (unless the command specifies a prefix argument
for the following command).
Some commands change the value of this variable during their
execution, simply as a flag for whatever command runs next. In
particular, the functions that kill text set `this-command' to
`kill-region' so that any kill commands immediately following
will know to append the killed text to the previous kill.
* Function: this-command-keys
This function returns a string containing the key sequence that
invoked the present command, plus any previous commands that
generated the prefix argument for this command.
(this-command-keys) ;; Now type `C-u C-x C-e'.
=> "^U^X^E"
* Variable: last-command-char
This variable is set to the last character that was typed on the
terminal and was part of a command. The principal use of this
variable is in `self-insert-command', which uses it to decide
which character to insert.
last-command-char ;; Now type `C-u C-x C-e'.
=> 5
The value is 5 because that is the ASCII code for `C-e'.
* Variable: echo-keystrokes
This variable determines how much time should elapse before
command characters are echoed. Its value must be an integer,
which specifies the number of seconds to wait before echoing.
If the user types a prefix key (say `C-x') and then delays this
many seconds before continuing, the key `C-x' is echoed in the
echo area. Any subsequent characters in the same command will
be echoed as well.
If the value is zero, then command input is not echoed.
The editor command loop reads keyboard input using
`read-key-sequence', which uses `read-char'. These and other
functions for keyboard input are also available for use in Lisp
programs. See also `momentary-string-display' in *Note Temporary
Displays::, and `sit-for' in *Note Waiting::. *Note Terminal
Input::, for functions and variables for controlling terminal input
modes and debugging terminal input.
* Function: read-char
This function reads a character from the command input (either
from direct keyboard input or from an executing keyboard macro),
and returns it.
No message is displayed to indicate that keyboard input is
expected. If you want to display a message, call `message'
first. If `cursor-in-echo-area' is non-`nil', then the cursor
moves to the echo area, to the end of any message displayed
there. Otherwise the cursor does not move. *Note The Echo
Area::.
In the first example, the user types `1' (which is ASCII code
49). The second example shows a keyboard macro definition that
calls `read-char' from the minibuffer. `read-char' reads the
keyboard macro's very next character, which is `1'. The value
of this function is displayed in the echo area by the command
`eval-expression'.
* Function: read-quoted-char &optional PROMPT
This function is like `read-char', except that if the first
character read is an octal digit (0-7), it reads up to two more
octal digits (but stopping if a non-octal digit is found) and
returns the character represented by those digits as an octal
number.
Quitting is suppressed when the first character is read, so that
the user can enter a `C-g'. *Note Quitting::.
If PROMPT is supplied, it specifies a string for prompting the
user. The prompt string is always printed in the echo area and
followed by a single `-'.
In the following example, the user types in the octal number 177
(which is 127 in decimal).
(read-quoted-char "What character")
---------- Echo Area ----------
What character-`177'
---------- Echo Area ----------
=> 127
* Function: read-key-sequence PROMPT
This function reads a key sequence and returns it as a string.
It keeps reading characters until it has accumulated a full key
sequence; that is, enough characters to specify a non-prefix
command using the current local and global keymaps.
`read-key-sequence' is used by the command loop to read command
input.
If an input character is an upper case letter and has no
definition, but the lower case equivalent is defined, then the
character is converted to lower case. Note that `lookup-key'
does not perform case conversion in this way.
Quitting is suppressed inside `read-key-sequence'. In other
words, a `C-g' typed while reading with this function is treated
like any other character, and `quit-flag' is not set. *Note
Quitting::.
The argument PROMPT is either a string to be displayed in the
echo area as a prompt, or `nil', meaning that no prompt is
displayed.
In the example below, the prompt `?' is displayed in the echo
area, and the user types `C-x C-f'.
(read-key-sequence "?")
---------- Echo Area ----------
?`C-x C-f'
---------- Echo Area ----------
=> "^X^F"
* Variable: unread-command-char
This variable holds a character waiting to be read as the next
input from the command input stream, or to the integer -1 if no
character is waiting. The variable is used because in some
cases an input function reads a character and then decides not
to use it. Storing the character in this variable causes it to
be processed normally by the command loop or when `read-char' is
next called.
For example, the function that governs prefix arguments reads
any number of digits. When it finds a non-digit character, it
must unread the character so that it becomes input for the next
command. Likewise, incremental search uses this feature to
unread a control character used to terminate the search.
* Function: input-pending-p
This function determines whether command input is currently
available. It returns immediately, with value `t' if there is
input, `nil' otherwise. On rare occasions it may return `t'
when no input is available.
* Variable: last-input-char
This variable records the last terminal input character read,
whether as part of a command or explicitly by a Lisp program.
In the example below, a character is read (the character `1',
ASCII code 49). It becomes the value of `last-input-char',
while `C-e' (from the `C-x C-e' command used to evaluate this
expression) remains the value of `last-command-char'.
* Function: discard-input
This function discards the contents of the terminal input buffer
and cancels any keyboard macro that might be in the process of
definition. It returns `nil'.
In the following example, the user may type a number of
characters right after starting the evaluation of the form.
After the `sleep-for' finishes sleeping, any characters that
have been typed are discarded.
Typing `C-g' while the command loop has run a Lisp function causes
Emacs to "quit" whatever it is doing. This means that control
returns to the innermost active command loop.
Typing `C-g' while the command loop is waiting for keyboard input
does not cause a quit; it acts as an ordinary input character. In
the simplest case, you cannot tell the difference, because `C-g'
normally runs the command `keyboard-quit', whose effect is to quit.
However, when `C-g' follows a prefix key, the result is an undefined
key. The effect is to cancel the prefix key as well as any prefix
argument.
In the minibuffer, `C-g' has a different definition: it aborts out
of the minibuffer. This means, in effect, that it exits the
minibuffer and then quits. (Simply quitting would return to the
command loop *within* the minibuffer.) The reason why `C-g' does not
quit directly when the command reader is reading input is so that its
meaning can be redefined in the minibuffer in this way. `C-g'
following a prefix key is not redefined in the minibuffer, and it has
its normal effect of canceling the prefix key and prefix argument.
This too would not be possible if `C-g' quit directly.
`C-g' causes a quit by setting the variable `quit-flag' to a
non-`nil' value. Emacs checks this variable at appropriate times and
quits if it is not `nil'. Setting `quit-flag' non-`nil' in any way
thus causes a quit.
At the level of C code, quits cannot happen just anywhere; only at
the special places which check `quit-flag'. The reason for this is
that quitting at other places might leave an inconsistency in Emacs's
internal state. Because quitting is delayed until a safe place,
quitting cannot make Emacs crash.
Certain functions such as `read-key-sequence' or
`read-quoted-char' prevent quitting entirely even though they wait
for input. Instead of quitting, `C-g' serves as the requested input.
In the case of `read-key-sequence', this serves to bring about the
special behavior of `C-g' in the command loop. In the case of
`read-quoted-char', this is so that `C-q' can be used to quote a
`C-g'.
You can prevent quitting for a portion of a Lisp function by
binding the variable `inhibit-quit' to a non-`nil' value. Then,
although `C-g' still sets `quit-flag' to `t' as usual, the usual
result of this--a quit--is prevented. Eventually, `inhibit-quit'
will become `nil' again, such as when its binding is unwound at the
end of a `let' form. At that time, if `quit-flag' is still
non-`nil', the requested quit happens immediately. This behavior is
ideal for a "critical section", where you wish to make sure that
quitting does not happen within that part of the program.
In some functions (such as `read-quoted-char'), `C-g' is handled
in a special way which does not involve quitting. This is done by
reading the input with `inhibit-quit' bound to `t' and setting
`quit-flag' to `nil' before `inhibit-quit' becomes `nil' again. This
excerpt from the definition of `read-quoted-char' shows how this is
done; it also shows that normal quitting is permitted after the first
character of input.
* Variable: quit-flag
If this variable is non-`nil', then Emacs quits immediately,
unless `inhibit-quit' is non-`nil'. Typing `C-g' sets
`quit-flag' non-`nil', regardless of `inhibit-quit'.
* Variable: inhibit-quit
This variable determines whether Emacs should quit when
`quit-flag' is set to a value other than `nil'. If
`inhibit-quit' is non-`nil', then `quit-flag' has no special
effect.
* Command: keyboard-quit
This function signals the `quit' condition with `(signal 'quit
nil)'. This is the same thing that quitting does. (See
`signal' in *Note Errors::.)
You can specify a character other than `C-g' to use for quitting.
See the function `set-input-mode' in *Note Terminal Input::.
Most Emacs commands can use a "prefix argument", a number
specified before the command itself. (Don't confuse prefix arguments
with prefix keys.) The prefix argument is represented by a value
that is always available (though it may be `nil', meaning there is no
prefix argument). Each command may use the prefix argument or ignore
it.
There are two representations of the prefix argument: "raw" and
"numeric". The editor command loop uses the raw representation
internally, and so do the Lisp variables that store the information,
but commands can request either representation.
Here are the possible values of a raw prefix argument:
* `nil', meaning there is no prefix argument. Its numeric value
is 1, but numerous commands make a distinction between `nil' and
the integer 1.
* An integer, which stands for itself.
* A list of one element, which is an integer. This form of prefix
argument results from one or a succession of `C-u''s with no
digits. The numeric value is the integer in the list, but some
commands make a distinction between such a list and an integer
alone.
* The symbol `-'. This indicates that `M--' or `C-u -' was typed,
without following digits. The equivalent numeric value is -1,
but some commands make a distinction between the integer -1 and
the symbol `-'.
The various possibilities may be illustrated by calling the
following function with various prefixes:
(defun print-prefix (arg)
"Print the value of the raw prefix arg at point."
(interactive "P")
(message "%s" arg))
Here are the results of calling `print-prefix' with various raw
prefix arguments:
There are two variables used to store the prefix argument:
`prefix-arg' and `current-prefix-arg'. Commands such as
`universal-argument' that set up prefix arguments for other commands
store them in `prefix-arg'. In contrast, `current-prefix-arg'
conveys the prefix argument to the current command, so setting it has
no effect on the prefix arguments for future commands.
Normally, commands specify which representation to use for the
prefix argument, either numeric or raw, in the `interactive'
declaration. (*Note Interactive Call::.) Alternatively, functions
may look at the value of the prefix argument directly in the variable
`current-prefix-arg', but this is less clean.
Don't call `universal-argument', `digit-argument', or
`negative-argument' unless you intend to let the user enter the
prefix argument for the *next* command.
* Command: universal-argument
This command reads input and specifies a prefix argument for the
following command. Don't call this command yourself unless you
know what you are doing.
* Command: digit-argument ARG
This command adds to the prefix argument for the following
command. The argument ARG is the raw prefix argument as it was
before this command; it is used to compute the updated prefix
argument. Don't call this command yourself unless you know what
you are doing.
* Command: negative-argument ARG
This command adds to the numeric argument for the next command.
The argument ARG is the raw prefix argument as it was before
this command; its value is negated to form the new prefix
argument. Don't call this command yourself unless you know what
you are doing.
* Function: prefix-numeric-value ARG
This function returns the numeric meaning of a valid raw prefix
argument value, ARG. The argument may be a symbol, a number, or
a list. If it is `nil', the value 1 is returned; if it is any
other symbol, the value -1 is returned. If it is a number, that
number is returned; if it is a list, the CAR of that list (which
should be a number) is returned.
* Variable: current-prefix-arg
This variable is the value of the raw prefix argument for the
*current* command. Commands may examine it directly, but the
usual way to access it is with `(interactive "P")'.
* Variable: prefix-arg
The value of this variable is the raw prefix argument for the
*next* editing command. Commands that specify prefix arguments
for the following command work by setting this variable.
The Emacs command loop is entered automatically when Emacs starts
up. This top-level invocation of the command loop is never exited
until the Emacs is killed. Lisp programs can also invoke the command
loop. Since this makes more than one activation of the command loop,
we call it "recursive editing". A recursive editing level has the
effect of suspending whatever command invoked it and permitting the
user to do arbitrary editing before resuming that command.
The commands available during recursive editing are the same ones
available in the top-level editing loop and defined in the keymaps.
Only a few special commands exit the recursive editing level; the
others return to the recursive editing level when finished. (The
special commands for exiting are always available, but do nothing
when recursive editing is not in progress.)
All command loops, including recursive ones, set up all-purpose
error handlers so that an error in a command run from the command
loop will not exit the loop.
Minibuffer input is a special kind of recursive editing. It has a
few special wrinkles, such as enabling display of the minibuffer and
the minibuffer window, but fewer than you might suppose. Certain
keys behave differently in the minibuffer, but that is only because
of the minibuffer's local map; if you switch windows, you get the
usual Emacs commands.
To invoke a recursive editing level, call the function
`recursive-edit'. This function contains the command loop; it also
contains a call to `catch' with tag `exit', which makes it possible
to exit the recursive editing level by throwing to `exit' (*note
Catch and Throw::.). If you throw a value other than `t', then
`recursive-edit' returns normally to the function that called it.
The command `C-M-c' (`exit-recursive-edit') does this. Throwing a
`t' value causes `recursive-edit' to quit, so that control returns to
the command loop one level up. This is called "aborting", and is
done by `C-]' (`abort-recursive-edit').
Most applications should not use recursive editing, except as part
of using the minibuffer. Usually it is more convenient for the user
if you change the major mode of the current buffer temporarily to a
special major mode, which has a command to go back to the previous
mode. (This technique is used by the `w' command in Rmail.) Or, if
you wish to give the user different text to edit "recursively",
create and select a new buffer in a special mode. In this mode,
define a command to complete the processing and go back to the
previous buffer. (The `m' command in Rmail does this.)
Recursive edits are useful in debugging. You can insert a call to
`debug' into a function definition as a sort of breakpoint, so that
you can look around when the function gets there. `debug' invokes a
recursive edit but also provides the other features of the debugger.
Recursive editing levels are also used when you type `C-r' in
`query-replace' or use `C-x q' (`kbd-macro-query').
* Function: recursive-edit
This function invokes the editor command loop. It is called
automatically by the initialization of Emacs, to let the user
begin editing. When called from a Lisp program, it enters a
recursive editing level.
In the following example, the function `simple-rec' first
advances point one word, then enters a recursive edit, printing
out a message in the echo area. The user can then do any
editing desired, and then type `C-M-c' to exit and continue
executing `simple-rec'.
* Command: exit-recursive-edit
This function exits from the innermost recursive edit (including
minibuffer input). Its definition is effectively `(throw 'exit
nil)'.
* Command: abort-recursive-edit
This function aborts the command that requested the innermost
recursive edit (including minibuffer input), by signaling `quit'
after exiting the recursive edit. Its definition is effectively
`(throw 'exit t)'. *Note Quitting::.
* Command: top-level
This function exits all recursive editing levels; it does not
return a value, as it jumps completely out of any computation
directly back to the main command loop.
* Function: recursion-depth
This function returns the current depth of recursive edits.
When no recursive edit is active, it returns 0.
"Disabling a command" marks the command as requiring user
confirmation before it can be executed. Disabling is used for
commands which might be confusing to beginning users, to prevent them
from using the commands by accident.
The low-level mechanism for disabling a command is to put a
non-`nil' `disabled' property on the Lisp symbol for the command.
These properties are normally set up by the user's `.emacs' file with
Lisp expressions such as this:
(put 'upcase-region 'disabled t)
For a few commands, these properties are present by default and may
be removed by the `.emacs' file.
If the value of the `disabled' property is a string, that string
is included in the message printed when the command is used:
(put 'delete-region 'disabled
"Text deleted this way cannot be yanked back!\n")
*Note : (emacs)Disabling, for the details on what happens when a
disabled command is invoked interactively. Disabling a command has
no effect on calling it as a function from Lisp programs.
* Command: enable-command COMMAND
Allow COMMAND to be executed without special confirmation from
now on. The user's `.emacs' file is optionally altered so that
this will apply to future sessions.
* Command: disable-command COMMAND
Require special confirmation to execute COMMAND from now on.
The user's `.emacs' file is optionally altered so that this will
apply to future sessions.
* Variable: disabled-command-hook
The value of this variable is a function to be called instead of
any command that is disabled (i.e., that has a non-`nil'
disabled property). By default, the value of
`disabled-command-hook' is a function defined to ask the user
whether to proceed.
The command loop keeps a history of the complex commands that have
been executed, to make it convenient to repeat these commands. A
"complex command" is one for which the interactive argument reading
uses the minibuffer. This includes any `M-x' command, any `M-ESC'
command, and any command whose `interactive' specification reads an
argument from the minibuffer. Explicit use of the minibuffer during
the execution of the command itself does not cause the command to be
considered complex.
* Variable: command-history
This variable's value is a list of recent complex commands, each
represented as a form to evaluate. It continues to accumulate
all complex commands for the duration of the editing session,
but all but the first (most recent) thirty elements are deleted
when a garbage collection takes place (*note Garbage
Collection::.).
There are a number of commands and even two entire modes devoted
to facilitating the editing and recall of previous commands. The
commands `repeat-complex-command', and `list-command-history' are
described in the user manual (*note : (emacs)Repetition.).
* Variable: repeat-complex-command-map
The value of this variable is a sparse keymap used by the
minibuffer inside of `read-complex-command'.
A "keyboard macro" is a canned sequence of keystrokes that can be
considered a command and made the definition of a key. Don't confuse
keyboard macros with Lisp macros (*note Macros::.).
* Function: execute-kbd-macro MACRO &optional COUNT
This function executes MACRO as a string of editor commands. If
MACRO is a string, then the characters in that string are
executed exactly as if they had been typed as command input.
If MACRO is a symbol, then its function definition is used in
place of MACRO. If that is another symbol, this process repeats.
Eventually the result should be a string. If the result is
neither a symbol nor a string, an error is signaled.
The argument COUNT is a repeat count; MACRO is executed that
many times. If COUNT is omitted or `nil', MACRO is executed
once. If it is 0, MACRO is executed over and over until it
encounters an error or a failing search.
* Variable: last-kbd-macro
This variable is the definition of the most recently defined
keyboard macro. Its value is a string or `nil'.
* Variable: executing-macro
This variable contains the string that defines the keyboard
macro that is currently executing. It is `nil' if no macro is
currently executing.
* Variable: defining-kbd-macro
This variable indicates whether a keyboard macro is being
defined. It is set to `t' by `start-kbd-macro', and `nil' by
`end-kbd-macro'. It is not hard to use this variable to make a
command behave differently when run from a keyboard macro
(perhaps indirectly by calling `interactive-p'). However, do
not set this variable yourself.
The user-level commands for defining, running and editing keyboard
macros include `call-last-kbd-macro', `insert-kbd-macro',
`start-kbd-macro', `end-kbd-macro', `kbd-macro-query', and
`name-last-kbd-macro'. They are described in the user's manual
(*note : (emacs)Keyboard Macros.).
The bindings between keyboard input and commands are recorded in
data structures called "keymaps". Each binding in a keymap
associates (or "binds") an individual character either with another
keymap or with a command. When a character is bound to a keymap,
that keymap is used to look up the next character typed; this
continues until a command is found. This process is called "key
lookup".
* Menu:
* Keymap Terms:: Definitions of terms pertaining to keymaps.
* Creating Keymaps:: Functions to create and copy keymaps.
* Key Lookup:: How extracting elements from keymaps works.
* Functions for Key Lookup:: How to request key lookup.
* Prefix Keys:: Defining a key with a keymap as its definition.
* Global and Local Keymaps:: Each buffer has a local keymap
to override the standard (global) bindings.
* Changing Key Bindings:: Redefining a key in a keymap.
* Key Binding Commands:: Interactive interfaces for redefining keys.
* Scanning Keymaps:: Looking through all keymaps, for printing help.
A "keymap" is a table mapping characters to definitions (which can
be any Lisp objects, though only certain types are meaningful for
execution by the command loop). Given a character and a keymap,
Emacs can get the character's definition.
A sequence of keyboard input characters that form a unit is called
a "key sequence", or "key" for short. A sequence of one character is
always a key sequence, and so are some multicharacter sequences.
A keymap determines a binding or definition for any key sequence.
If the key sequence is a single character, its binding is the
definition of the character in the keymap. The binding of a
multicharacter key sequence is found by an iterative process: the
binding of the first character is found, and must be a keymap; then
the second character's binding is found in that keymap, and so on
until all the characters in the key sequence are used up.
If the binding of a key sequence is a keymap, we call the key
sequence a "prefix key". Otherwise, we call it a "complete key"
(because no more characters can be added to it). If the binding is
`nil', we call the key "undefined". Examples of prefix keys are
`C-c', `C-x', and `C-x 4'. Examples of defined complete keys are
`X', RET, and `C-x 4 C-f'. Examples of undefined complete keys are
`C-x C-g', and `C-c 3'. *Note Prefix Keys::, for more details.
The rule for finding the binding of a key sequence assumes that
the intermediate bindings (found for the characters before the last)
are all keymaps; if this is not so, the sequence of characters does
not form a unit--it is not really a key sequence. In other words,
removing one or more characters from the end of any key must always
yield a prefix key. For example, `C-f C-f' is not a key; `C-f' is
not a prefix key, so a longer sequence starting with `C-f' cannot be
a key. Note that the set of possible multicharacter key sequences
depends on the bindings for prefix keys; therefore, it can be
different for different keymaps, and can change when bindings are
changed. However, a one-character sequence is always a key sequence,
because it does not depend on any prefix keys for its validity.
At any time, two primary keymaps are in use for finding key
bindings: the "global map", which is shared by all buffers, and the
"local keymap", which is usually associated with a specific major
mode. The local keymap bindings shadow (i.e., take precedence over)
the corresponding global bindings. *Note Global and Local Keymaps::,
for details.
A keymap can be represented as one of two kinds of Lisp object: a
vector or a list. A "full keymap" is a vector of length 128. The
binding for a character in such a keymap is found by indexing into
the vector with the character as the index.
A "sparse keymap" is a list whose CAR is the symbol `keymap', and
whose remaining elements are cons cells of the form `(CHAR .
BINDING)'. It is called a sparse keymap because it stores only the
entries which are significant. Use a sparse keymap when you expect
only a few entries. (`define-key' automatically creates sparse
keymaps for intermediate keymaps.)
Keymaps record directly only character codes less than 128; they
are unable to handle directly the META characters, whose codes are
from 128 to 255. Instead, META characters are regarded for purposes
of key lookup as sequences of two characters, the first of which is
ESC (the usual value of `meta-prefix-char'). Thus, the key `M-a' is
really represented as `ESC a', and its global binding is found at the
slot for `a' in `esc-map'.
Here as an example is the local keymap for Lisp mode, a sparse
keymap. It defines `C-c C-l' as the `run-lisp' command, `M-C-q' as
`indent-sexp', and `M-C-x' as `lisp-send-defun'.
* Function: keymapp OBJECT
This function returns `t' if OBJECT is a keymap, `nil'
otherwise. A keymap is either a vector of length 128, or a list
with the form `(keymap PAIRS...)', where PAIRS stands for a
series of associations, cons cells of the form `(CHAR . BINDING)'.
(keymapp '(keymap))
=> t
(keymapp (current-global-map))
=> t
* Function: make-keymap
This function creates and returns a new full keymap (i.e., a
vector of length 128). All entries in the keymap are `nil',
which means that no characters are defined.
(make-keymap)
=> [nil nil nil ... nil nil]
* Function: make-sparse-keymap
This function creates and returns a new sparse keymap with no
entries. In this keymap, no characters are defined.
(make-sparse-keymap)
=> (keymap)
* Function: copy-keymap KEYMAP
This function returns a copy of KEYMAP. Any keymaps which
appear directly as bindings in KEYMAP are also copied
recursively, and so on to any number of levels. However,
recursive copying does not take place when the definition of a
character is a symbol whose function definition is a keymap; the
same symbol appears in the new copy.
