A minibuffer is a special buffer that Emacs commands use to read arguments more complicated than the single numeric prefix argument. These arguments include file names, buffer names, and command names (as in M-x). The minibuffer is displayed on the bottom line of the frame, in the same place as the echo area, but only while it is in use for reading an argument.
In most ways, a minibuffer is a normal Emacs buffer. Most operations within a buffer, such as editing commands, work normally in a minibuffer. However, many operations for managing buffers do not apply to minibuffers. The name of a minibuffer always has the form ` *Minibuf-number', and it cannot be changed. Minibuffers are displayed only in special windows used only for minibuffers; these windows always appear at the bottom of a frame. (Sometimes frames have no minibuffer window, and sometimes a special kind of frame contains nothing but a minibuffer window; see section Minibuffers and Frames.)
The minibuffer's window is normally a single line. You can resize it temporarily with the window sizing commands; it reverts to its normal size when the minibuffer is exited. You can resize it permanently by using the window sizing commands in the frame's other window, when the minibuffer is not active. If the frame contains just a minibuffer, you can change the minibuffer's size by changing the frame's size.
If a command uses a minibuffer while there is an active
minibuffer, this is called a recursive minibuffer. The
first minibuffer is named ` *Minibuf-0*'. Recursive
minibuffers are named by incrementing the number at the end of the
name. (The names begin with a space so that they won't show up in
normal buffer lists.) Of several recursive minibuffers, the
innermost (or most recently entered) is the active minibuffer. We
usually call this "the" minibuffer. You can permit or forbid
recursive minibuffers by setting the variable
enable-recursive-minibuffers or by putting properties
of that name on command symbols (see section Minibuffer Miscellany).
Like other buffers, a minibuffer may use any of several local keymaps (see section Keymaps); these contain various exit commands and in some cases completion commands (see section Completion).
minibuffer-local-map is for ordinary input (no
completion).
minibuffer-local-ns-map is similar, except that
SPC exits just like RET. This is used mainly
for Mocklisp compatibility.
minibuffer-local-completion-map is for permissive
completion.
minibuffer-local-must-match-map is for strict
completion and for cautious completion.
Most often, the minibuffer is used to read text as a string. It
can also be used to read a Lisp object in textual form. The most
basic primitive for minibuffer input is
read-from-minibuffer; it can do either one.
In most cases, you should not call minibuffer input functions in
the middle of a Lisp function. Instead, do all minibuffer input as
part of reading the arguments for a command, in the
interactive specification. See section Defining Commands.
nil, then it uses
read to convert the text into a Lisp object (see
section Input Functions). The first thing this function does is to activate a minibuffer and display it with prompt-string as the prompt. This value must be a string. Then the user can edit text in the minibuffer.
When the user types a command to exit the minibuffer,
read-from-minibuffer constructs the return value from
the text in the minibuffer. Normally it returns a string containing
that text. However, if read is non-nil,
read-from-minibuffer reads the text and returns the
resulting Lisp object, unevaluated. (See section Input Functions, for information about
reading.)
The argument default specifies a default value to
make available through the history commands. It should be a string,
or nil. If read is non-nil,
then default is also used as the input to
read, if the user enters empty input. However, in the
usual case (where read is nil),
read-from-minibuffer does not return
default when the user enters empty input; it returns an
empty string, "". In this respect, it is different
from all the other minibuffer input functions in this chapter.
If keymap is non-nil, that keymap is the
local keymap to use in the minibuffer. If keymap is
omitted or nil, the value of
minibuffer-local-map is used as the keymap. Specifying
a keymap is the most important way to customize the minibuffer for
various applications such as completion.
The argument hist specifies which history list
variable to use for saving the input and for history commands used
in the minibuffer. It defaults to minibuffer-history.
See section Minibuffer History.
If the variable minibuffer-allow-text-properties is
non-nil, then the string which is returned includes
whatever text properties were present in the minibuffer. Otherwise
all the text properties are stripped when the value is
returned.
If the argument inherit-input-method is
non-nil, then the minibuffer inherits the current
input method (see section Input
Methods) and the setting of
enable-multibyte-characters (see section Text Representations) from whichever
buffer was current before entering the minibuffer.
If initial-contents is a string,
read-from-minibuffer inserts it into the minibuffer,
leaving point at the end, before the user starts to edit the text.
The minibuffer appears with this text as its initial contents.
Alternatively, initial-contents can be a cons cell of
the form (string . position).
This means to insert string in the minibuffer but put
point position characters from the beginning, rather
than at the end.
Usage note: The initial-contents
argument and the default argument are two alternative
features for more or less the same job. It does not make sense to
use both features in a single call to
read-from-minibuffer. In general, we recommend using
default, since this permits the user to insert the
default value when it is wanted, but does not burden the user with
deleting it from the minibuffer on other occasions.
read-from-minibuffer. The keymap used is
minibuffer-local-map. The optional argument history, if non-nil, specifies a history list and optionally the initial position in the list. The optional argument default specifies a default value to return if the user enters null input; it should be a string. The optional argument inherit-input-method specifies whether to inherit the current buffer's input method.
This function is a simplified interface to the
read-from-minibuffer function:
(read-string prompt initial history default inherit)
==
(let ((value
(read-from-minibuffer prompt initial nil nil
history default inherit)))
(if (equal value "")
default
value))
nil, then read-from-minibuffer strips all
text properties from the minibuffer input before returning it.
Since all minibuffer input uses read-from-minibuffer,
this variable applies to all minibuffer input. Note that the completion functions discard text properties unconditionally, regardless of the value of this variable.
exit-minibufferexit-minibufferabort-recursive-editnext-history-elementprevious-history-elementnext-matching-history-elementprevious-matching-history-elementread-from-minibuffer. This is a simplified interface to the
read-from-minibuffer function, and passes the value of
the minibuffer-local-ns-map keymap as the
keymap argument for that function. Since the keymap
minibuffer-local-ns-map does not rebind
C-q, it is possible to put a space into the
string, by quoting it.
(read-no-blanks-input prompt initial) == (read-from-minibuffer prompt initial minibuffer-local-ns-map)
read-no-blanks-input. By default, it makes the
following bindings, in addition to those of
minibuffer-local-map: exit-minibufferexit-minibufferself-insert-and-exitThis section describes functions for reading Lisp objects with the minibuffer.
read-from-minibuffer. This is a simplified interface to the
read-from-minibuffer function:
(read-minibuffer prompt initial) == (read-from-minibuffer prompt initial nil t)
Here is an example in which we supply the string
"(testing)" as initial input:
(read-minibuffer "Enter an expression: " (format "%s" '(testing))) ;; Here is how the minibuffer is displayed: ---------- Buffer: Minibuffer ---------- Enter an expression: (testing)-!- ---------- Buffer: Minibuffer ----------
The user can type RET immediately to use the initial input as a default, or can edit the input.
read-from-minibuffer. This function simply evaluates the result of a call to
read-minibuffer:
(eval-minibuffer prompt initial) == (eval (read-minibuffer prompt initial))
eval-minibuffer is that here
the initial form is not optional and it is treated as a
Lisp object to be converted to printed representation rather than
as a string of text. It is printed with prin1, so if
it is a string, double-quote characters (`"') appear
in the initial text. See section Output
Functions. The first thing edit-and-eval-command does is to
activate the minibuffer with prompt as the prompt. Then
it inserts the printed representation of form in the
minibuffer, and lets the user edit it. When the user exits the
minibuffer, the edited text is read with read and then
evaluated. The resulting value becomes the value of
edit-and-eval-command.
In the following example, we offer the user an expression with initial text which is a valid form already:
(edit-and-eval-command "Please edit: " '(forward-word 1)) ;; After evaluation of the preceding expression, ;; the following appears in the minibuffer: ---------- Buffer: Minibuffer ---------- Please edit: (forward-word 1)-!- ---------- Buffer: Minibuffer ----------
Typing RET right away would exit the minibuffer and
evaluate the expression, thus moving point forward one word.
edit-and-eval-command returns nil in this
example.
A minibuffer history list records previous minibuffer inputs so the user can reuse them conveniently. A history list is actually a symbol, not a list; it is a variable whose value is a list of strings (previous inputs), most recent first.
There are many separate history lists, used for different kinds of inputs. It's the Lisp programmer's job to specify the right history list for each use of the minibuffer.
The basic minibuffer input functions
read-from-minibuffer and completing-read
both accept an optional argument named hist which is how
you specify the history list. Here are the possible values:
If you don't specify hist, then the default history
list minibuffer-history is used. For other standard
history lists, see below. You can also create your own history list
variable; just initialize it to nil before the first
use.
Both read-from-minibuffer and
completing-read add new elements to the history list
automatically, and provide commands to allow the user to reuse
items on the list. The only thing your program needs to do to use a
history list is to initialize it and to pass its name to the input
functions when you wish. But it is safe to modify the list by hand
when the minibuffer input functions are not using it.
Here are some of the standard minibuffer history list variables:
query-replace (and similar arguments to other
commands).
Completion is a feature that fills in the rest of a
name starting from an abbreviation for it. Completion works by
comparing the user's input against a list of valid names and
determining how much of the name is determined uniquely by what the
user has typed. For example, when you type C-x b
(switch-to-buffer) and then type the first few letters
of the name of the buffer to which you wish to switch, and then
type TAB (minibuffer-complete), Emacs
extends the name as far as it can.
Standard Emacs commands offer completion for names of symbols, files, buffers, and processes; with the functions in this section, you can implement completion for other kinds of names.
The try-completion function is the basic primitive
for completion: it returns the longest determined completion of a
given initial string, with a given set of strings to match
against.
The function completing-read provides a
higher-level interface for completion. A call to
completing-read specifies how to determine the list of
valid names. The function then activates the minibuffer with a
local keymap that binds a few keys to commands useful for
completion. Other functions provide convenient simple interfaces
for reading certain kinds of names with completion.
The two functions try-completion and
all-completions have nothing in themselves to do with
minibuffers. We describe them in this chapter so as to keep them
near the higher-level completion features that do use the
minibuffer.
Completion compares string against each of the
permissible completions specified by collection; if the
beginning of the permissible completion equals string,
it matches. If no permissible completions match,
try-completion returns nil. If only one
permissible completion matches, and the match is exact, then
try-completion returns t. Otherwise, the
value is the longest initial sequence common to all the permissible
completions that match.
If collection is an alist (see section Association Lists), the CARs of the alist elements form the set of permissible completions.
If collection is an
obarray (see section Creating and
Interning Symbols), the names of all symbols in the obarray
form the set of permissible completions. The global variable
obarray holds an obarray containing the names of all
interned Lisp symbols.
Note that the only valid way to make a new obarray is to create
it empty and then add symbols to it one by one using
intern. Also, you cannot intern a given symbol in more
than one obarray.
If the argument predicate is non-nil,
then it must be a function of one argument. It is used to test each
possible match, and the match is accepted only if
predicate returns non-nil. The argument
given to predicate is either a cons cell from the alist
(the CAR of which is a string) or else it is a symbol (not
a symbol name) from the obarray.
You can also use a symbol that is a function as
collection. Then the function is solely responsible for
performing completion; try-completion returns whatever
this function returns. The function is called with three arguments:
string, predicate and nil. (The
reason for the third argument is so that the same function can be
used in all-completions and do the appropriate thing
in either case.) See section Programmed
Completion.
In the first of the following examples, the string
`foo' is matched by three of the alist CARs. All of
the matches begin with the characters `fooba', so that
is the result. In the second example, there is only one possible
match, and it is exact, so the value is t.
(try-completion
"foo"
'(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)))
=> "fooba"
(try-completion "foo" '(("barfoo" 2) ("foo" 3)))
=> t
In the following example, numerous symbols begin with the characters `forw', and all of them begin with the word `forward'. In most of the symbols, this is followed with a `-', but not in all, so no more than `forward' can be completed.
(try-completion "forw" obarray)
=> "forward"
Finally, in the following example, only two of the three
possible matches pass the predicate test (the string
`foobaz' is too short). Both of those begin with the
string `foobar'.
(defun test (s)
(> (length (car s)) 6))
=> test
(try-completion
"foo"
'(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
'test)
=> "foobar"
try-completion.
If collection is a function, it is called with three
arguments: string, predicate and
t; then all-completions returns whatever
the function returns. See section Programmed Completion.
If nospace is non-nil, completions that
start with a space are ignored unless string also starts
with a space.
Here is an example, using the function test shown
in the example for try-completion:
(defun test (s)
(> (length (car s)) 6))
=> test
(all-completions
"foo"
'(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
'test)
=> ("foobar1" "foobar2")
nil, Emacs does not consider case significant
in completion.
This section describes the basic interface for reading from the minibuffer with completion.
The actual completion is done by passing collection
and predicate to the function
try-completion. This happens in certain commands bound
in the local keymaps used for completion.
If require-match is nil, the exit
commands work regardless of the input in the minibuffer. If
require-match is t, the usual minibuffer
exit commands won't exit unless the input completes to an element
of collection. If require-match is neither
nil nor t, then the exit commands won't
exit unless the input already in the buffer matches an element of
collection.
However, empty input is always permitted, regardless of the
value of require-match; in that case,
completing-read returns default. The value
of default (if non-nil) is also available
to the user through the history commands.
The user can exit with null input by typing RET with
an empty minibuffer. Then completing-read returns
"". This is how the user requests whatever default the
command uses for the value being read. The user can return using
RET in this way regardless of the value of
require-match, and regardless of whether the empty
string is included in collection.
The function completing-read works by calling
read-minibuffer. It uses
minibuffer-local-completion-map as the keymap if
require-match is nil, and uses
minibuffer-local-must-match-map if
require-match is non-nil. See section Minibuffer Commands That Do
Completion.
The argument hist specifies which history list
variable to use for saving the input and for minibuffer history
commands. It defaults to minibuffer-history. See
section Minibuffer History.
If initial is non-nil,
completing-read inserts it into the minibuffer as part
of the input. Then it allows the user to edit the input, providing
several commands to attempt completion. In most cases, we recommend
using default, and not initial.
If the argument inherit-input-method is
non-nil, then the minibuffer inherits the current
input method (see section Input
Methods) and the setting of
enable-multibyte-characters (see section Text Representations) from whichever
buffer was current before entering the minibuffer.
Completion ignores case when comparing the input against the
possible matches, if the built-in variable
completion-ignore-case is non-nil. See
section Basic Completion
Functions.
Here's an example of using completing-read:
(completing-read
"Complete a foo: "
'(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
nil t "fo")
;; After evaluation of the preceding expression,
;; the following appears in the minibuffer:
---------- Buffer: Minibuffer ----------
Complete a foo: fo-!-
---------- Buffer: Minibuffer ----------
If the user then types DEL DEL b
RET, completing-read returns
barfoo.
The completing-read function binds three variables
to pass information to the commands that actually do completion.
These variables are minibuffer-completion-table,
minibuffer-completion-predicate and
minibuffer-completion-confirm. For more information
about them, see section Minibuffer
Commands That Do Completion.
This section describes the keymaps, commands and user options used in the minibuffer to do completion.
completing-read
uses this value as the local keymap when an exact match of one of
the completions is not required. By default, this keymap makes the
following bindings: minibuffer-completion-helpminibuffer-complete-wordminibuffer-completewith other characters bound as in
minibuffer-local-map (see section Reading Text Strings with the
Minibuffer).
completing-read
uses this value as the local keymap when an exact match of one of
the completions is required. Therefore, no keys are bound to
exit-minibuffer, the command that exits the minibuffer
unconditionally. By default, this keymap makes the following
bindings: minibuffer-completion-helpminibuffer-complete-wordminibuffer-completeminibuffer-complete-and-exitminibuffer-complete-and-exitwith other characters bound as in
minibuffer-local-map.
completing-read
passes to try-completion. It is used by minibuffer
completion commands such as
minibuffer-complete-word.
completing-read passes to
try-completion. The variable is also used by the other
minibuffer completion functions.
minibuffer-complete-word does not add any characters
beyond the first character that is not a word constituent. See
section Syntax Tables.
minibuffer-completion-confirm is
nil. If confirmation is required, it is given
by repeating this command immediately--the command is programmed to
work without confirmation when run twice in succession.
nil, Emacs asks for confirmation of a
completion before exiting the minibuffer. The function
minibuffer-complete-and-exit checks the value of this
variable before it exits.
all-completions using the value of
the variable minibuffer-completion-table as the
collection argument, and the value of
minibuffer-completion-predicate as the
predicate argument. The list of completions is displayed
as text in a buffer named `*Completions*'.
standard-output, usually a buffer. (See section Reading and Printing Lisp Objects, for
more information about streams.) The argument
completions is normally a list of completions just
returned by all-completions, but it does not have to
be. Each element may be a symbol or a string, either of which is
simply printed, or a list of two strings, which is printed as if
the strings were concatenated. This function is called by
minibuffer-completion-help. The most common way to use
it is together with with-output-to-temp-buffer, like
this:
(with-output-to-temp-buffer "*Completions*"
(display-completion-list
(all-completions (buffer-string) my-alist)))
nil, the completion commands automatically display
a list of possible completions whenever nothing can be completed
because the next character is not uniquely determined.
This section describes the higher-level convenient functions for reading certain sorts of names with completion.
In most cases, you should not call these functions in the middle
of a Lisp function. When possible, do all minibuffer input as part
of reading the arguments for a command, in the
interactive specification. See section Defining Commands.
nil, it should be a string or a buffer. It is
mentioned in the prompt, but is not inserted in the minibuffer as
initial input. If existing is non-nil, then the name
specified must be that of an existing buffer. The usual commands to
exit the minibuffer do not exit if the text is not valid, and
RET does completion to attempt to find a valid name.
(However, default is not checked for validity; it is
returned, whatever it is, if the user exits with the minibuffer
empty.)
In the following example, the user enters
`minibuffer.t', and then types RET. The
argument existing is t, and the only buffer
name starting with the given input is
`minibuffer.texi', so that name is the value.
(read-buffer "Buffer name? " "foo" t)
;; After evaluation of the preceding expression,
;; the following prompt appears,
;; with an empty minibuffer:
---------- Buffer: Minibuffer ----------
Buffer name? (default foo) -!-
---------- Buffer: Minibuffer ----------
;; The user types minibuffer.t RET.
=> "minibuffer.texi"
iswitchb-read-buffer, all Emacs commands that call
read-buffer to read a buffer name will actually use
the iswitchb package to read it.
read-from-minibuffer.
Recall that a command is anything for which commandp
returns t, and a command name is a symbol for which
commandp returns t. See section Interactive Call. The argument default specifies what to return if the
user enters null input. It can be a symbol or a string; if it is a
string, read-command interns it before returning it.
If default is nil, that means no default
has been specified; then if the user enters null input, the return
value is nil.
(read-command "Command name? ") ;; After evaluation of the preceding expression, ;; the following prompt appears with an empty minibuffer: ---------- Buffer: Minibuffer ---------- Command name? ---------- Buffer: Minibuffer ----------
If the user types forward-c RET, then this function
returns forward-char.
The read-command function is a simplified interface
to completing-read. It uses the variable
obarray so as to complete in the set of extant Lisp
symbols, and it uses the commandp predicate so as to
accept only command names:
(read-command prompt)
==
(intern (completing-read prompt obarray
'commandp t nil))
The argument default specifies what to return if the
user enters null input. It can be a symbol or a string; if it is a
string, read-variable interns it before returning it.
If default is nil, that means no default
has been specified; then if the user enters null input, the return
value is nil.
(read-variable "Variable name? ") ;; After evaluation of the preceding expression, ;; the following prompt appears, ;; with an empty minibuffer: ---------- Buffer: Minibuffer ---------- Variable name? -!- ---------- Buffer: Minibuffer ----------
If the user then types fill-p RET,
read-variable returns fill-prefix.
This function is similar to read-command, but uses
the predicate user-variable-p instead of
commandp:
(read-variable prompt)
==
(intern
(completing-read prompt obarray
'user-variable-p t nil))
See also the functions read-coding-system and
read-non-nil-coding-system, in section User-Chosen Coding Systems.
Here is another high-level completion function, designed for reading a file name. It provides special features including automatic insertion of the default directory.
nil, then the function returns default
if the user just types RET. default is not
checked for validity; it is returned, whatever it is, if the user
exits with the minibuffer empty. If existing is non-nil, then the user
must specify the name of an existing file; RET performs
completion to make the name valid if possible, and then refuses to
exit if it is not valid. If the value of existing is
neither nil nor t, then RET
also requires confirmation after completion. If existing
is nil, then the name of a nonexistent file is
acceptable.
The argument directory specifies the directory to use
for completion of relative file names. If
insert-default-directory is non-nil,
directory is also inserted in the minibuffer as initial
input. It defaults to the current buffer's value of
default-directory.
If you specify initial, that is an initial file name
to insert in the buffer (after directory, if that is
inserted). In this case, point goes at the beginning of
initial. The default for initial is
nil---don't insert any file name. To see what
initial does, try the command C-x C-v.
Note: we recommend using default rather
than initial in most cases.
Here is an example:
(read-file-name "The file is ") ;; After evaluation of the preceding expression, ;; the following appears in the minibuffer: ---------- Buffer: Minibuffer ---------- The file is /gp/gnu/elisp/-!- ---------- Buffer: Minibuffer ----------
Typing manual TAB results in the following:
---------- Buffer: Minibuffer ---------- The file is /gp/gnu/elisp/manual.texi-!- ---------- Buffer: Minibuffer ----------
If the user types RET, read-file-name
returns the file name as the string
"/gp/gnu/elisp/manual.texi".
read-file-name. Its value controls whether
read-file-name starts by placing the name of the
default directory in the minibuffer, plus the initial file name if
any. If the value of this variable is nil, then
read-file-name does not place any initial input in the
minibuffer (unless you specify initial input with the
initial argument). In that case, the default directory
is still used for completion of relative file names, but is not
displayed. For example:
;; Here the minibuffer starts out with the default directory. (let ((insert-default-directory t)) (read-file-name "The file is ")) ---------- Buffer: Minibuffer ---------- The file is ~lewis/manual/-!- ---------- Buffer: Minibuffer ---------- ;; Here the minibuffer is empty and only the prompt ;; appears on its line. (let ((insert-default-directory nil)) (read-file-name "The file is ")) ---------- Buffer: Minibuffer ---------- The file is -!- ---------- Buffer: Minibuffer ----------
Sometimes it is not possible to create an alist or an obarray containing all the intended possible completions. In such a case, you can supply your own function to compute the completion of a given string. This is called programmed completion.
To use this feature, pass a symbol with a function definition as
the collection argument to completing-read.
The function completing-read arranges to pass your
completion function along to try-completion and
all-completions, which will then let your function do
all the work.
The completion function should accept three arguments:
nil if none. Your function should call the predicate
for each possible match, and ignore the possible match if the
predicate returns nil.
There are three flag values for three operations:
nil specifies try-completion. The
completion function should return the completion of the specified
string, or t if the string is a unique and exact match
already, or nil if the string matches no possibility.
If the string is an exact match for one possibility, but also
matches other longer possibilities, the function should return the
string, not t.
t specifies all-completions. The
completion function should return a list of all possible
completions of the specified string.
lambda specifies a test for an exact match. The
completion function should return t if the specified
string is an exact match for some possibility; nil
otherwise.
It would be consistent and clean for completion functions to allow lambda expressions (lists that are functions) as well as function symbols as collection, but this is impossible. Lists as completion tables are already assigned another meaning--as alists. It would be unreliable to fail to handle an alist normally because it is also a possible function. So you must arrange for any function you wish to use for completion to be encapsulated in a symbol.
Emacs uses programmed completion when completing file names. See section File Name Completion.
This section describes functions used to ask the user a
yes-or-no question. The function y-or-n-p can be
answered with a single character; it is useful for questions where
an inadvertent wrong answer will not have serious consequences.
yes-or-no-p is suitable for more momentous questions,
since it requires three or four characters to answer.
If either of these functions is called in a command that was
invoked using the mouse--more precisely, if
last-nonmenu-event (see section Information from the Command Loop) is
either nil or a list--then it uses a dialog box or
pop-up menu to ask the question. Otherwise, it uses keyboard input.
You can force use of the mouse or use of keyboard input by binding
last-nonmenu-event to a suitable value around the
call.
Strictly speaking, yes-or-no-p uses the minibuffer
and y-or-n-p does not; but it seems best to describe
them together.
t if the user types y, nil if
the user types n. This function also accepts
SPC to mean yes and DEL to mean no. It
accepts C-] to mean "quit", like C-g, because
the question might look like a minibuffer and for that reason the
user might try to use C-] to get out. The answer is a
single character, with no RET needed to terminate it.
Upper and lower case are equivalent. "Asking the question" means printing prompt in the echo area, followed by the string `(y or n) '. If the input is not one of the expected answers (y, n, SPC, DEL, or something that quits), the function responds `Please answer y or n.', and repeats the request.
This function does not actually use the minibuffer, since it does not allow editing of the answer. It actually uses the echo area (see section The Echo Area), which uses the same screen space as the minibuffer. The cursor moves to the echo area while the question is being asked.
The answers and their meanings, even `y' and
`n', are not hardwired. The keymap
query-replace-map specifies them. See section Search and Replace.
In the following example, the user first types q, which is invalid. At the next prompt the user types y.
(y-or-n-p "Do you need a lift? ") ;; After evaluation of the preceding expression, ;; the following prompt appears in the echo area: ---------- Echo area ---------- Do you need a lift? (y or n) ---------- Echo area ---------- ;; If the user then types q, the following appears: ---------- Echo area ---------- Please answer y or n. Do you need a lift? (y or n) ---------- Echo area ---------- ;; When the user types a valid answer, ;; it is displayed after the question: ---------- Echo area ---------- Do you need a lift? (y or n) y ---------- Echo area ----------
We show successive lines of echo area messages, but only one actually appears on the screen at a time.
y-or-n-p,
except that if the user fails to answer within seconds
seconds, this function stops waiting and returns
default-value. It works by setting up a timer; see
section Timers for Delayed
Execution. The argument seconds may be an integer or
a floating point number.
t if the user enters `yes',
nil if the user types `no'. The user must
type RET to finalize the response. Upper and lower case
are equivalent. yes-or-no-p starts by displaying prompt
in the echo area, followed by `(yes or no) '. The user
must type one of the expected responses; otherwise, the function
responds `Please answer yes or no.', waits about two
seconds and repeats the request.
yes-or-no-p requires more work from the user than
y-or-n-p and is appropriate for more crucial
decisions.
Here is an example:
(yes-or-no-p "Do you really want to remove everything? ") ;; After evaluation of the preceding expression, ;; the following prompt appears, ;; with an empty minibuffer: ---------- Buffer: minibuffer ---------- Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ----------
If the user first types y RET, which is invalid because this function demands the entire word `yes', it responds by displaying these prompts, with a brief pause between them:
---------- Buffer: minibuffer ---------- Please answer yes or no. Do you really want to remove everything? (yes or no) ---------- Buffer: minibuffer ----------
When you have a series of similar questions to ask, such as "Do
you want to save this buffer" for each buffer in turn, you should
use map-y-or-n-p to ask the collection of questions,
rather than asking each question individually. This gives the user
certain convenient facilities such as the ability to answer the
whole series at once.
The value of list specifies the objects to ask
questions about. It should be either a list of objects or a
generator function. If it is a function, it should expect no
arguments, and should return either the next object to ask about,
or nil meaning stop asking questions.
The argument prompter specifies how to ask each question. If prompter is a string, the question text is computed like this:
(format prompter object)
where object is the next object to ask about (as obtained from list).
If not a string, prompter should be a function of one
argument (the next object to ask about) and should return the
question text. If the value is a string, that is the question to
ask the user. The function can also return t meaning
do act on this object (and don't ask the user), or nil
meaning ignore this object (and don't ask the user).
The argument actor says how to act on the answers that the user gives. It should be a function of one argument, and it is called with each object that the user says yes for. Its argument is always an object obtained from list.
If the argument help is given, it should be a list of this form:
(singular plural action)
where singular is a string containing a singular noun that describes the objects conceptually being acted on, plural is the corresponding plural noun, and action is a transitive verb describing what actor does.
If you don't specify help, the default is
("object" "objects" "act on").
Each time a question is asked, the user may enter y,
Y, or SPC to act on that object;
n, N, or DEL to skip that object;
! to act on all following objects; ESC or
q to exit (skip all following objects); .
(period) to act on the current object and then exit; or
C-h to get help. These are the same answers that
query-replace accepts. The keymap
query-replace-map defines their meaning for
map-y-or-n-p as well as for
query-replace; see section Search and Replace.
You can use action-alist to specify additional
possible answers and what they mean. It is an alist of elements of
the form (char function
help), each of which defines one additional
answer. In this element, char is a character (the
answer); function is a function of one argument (an
object from list); help is a string.
When the user responds with char,
map-y-or-n-p calls function. If it returns
non-nil, the object is considered "acted upon", and
map-y-or-n-p advances to the next object in
list. If it returns nil, the prompt is
repeated for the same object.
If map-y-or-n-p is called in a command that was
invoked using the mouse--more precisely, if
last-nonmenu-event (see section Information from the Command Loop) is
either nil or a list--then it uses a dialog box or
pop-up menu to ask the question. In this case, it does not use
keyboard input or the echo area. You can force use of the mouse or
use of keyboard input by binding last-nonmenu-event to
a suitable value around the call.
The return value of map-y-or-n-p is the number of
objects acted on.
To read a password to pass to another program, you can use the
function read-passwd.
The optional argument confirm, if
non-nil, says to read the password twice and insist it
must be the same both times. If it isn't the same, the user has to
type it over and over until the last two times match.
The optional argument default specifies the default
password to return if the user enters empty input. If
default is nil, then
read-passwd returns the null string in that case.
This section describes some basic functions and variables related to minibuffers.
last-command-char; see section Information from the Command
Loop).
nil.
help-form locally inside
the minibuffer (see section Help
Functions).
nil if none is
currently active.
nil, that stands for the current
frame. Note that the minibuffer window used by a frame need not be
part of that frame--a frame that has no minibuffer of its own
necessarily uses some other frame's minibuffer window.
nil if window is a minibuffer
window.
It is not correct to determine whether a given window is a
minibuffer by comparing it with the result of
(minibuffer-window), because there can be more than
one minibuffer window if there is more than one frame.
nil if window, assumed to be a
minibuffer window, is currently active.
nil, it should be a window object. When the
function scroll-other-window is called in the
minibuffer, it scrolls this window.
Finally, some functions and variables deal with recursive minibuffers (see section Recursive Editing):
nil, you can invoke commands (such as
find-file) that use minibuffers even while the
minibuffer window is active. Such invocation produces a recursive
editing level for a new minibuffer. The outer-level minibuffer is
invisible while you are editing the inner one. If this variable is nil, you cannot invoke
minibuffer commands when the minibuffer window is active, not even
if you switch to another window to do it.
If a command name has a property
enable-recursive-minibuffers that is
non-nil, then the command can use the minibuffer to
read arguments even if it is invoked from the minibuffer. The
minibuffer command next-matching-history-element
(normally M-s in the minibuffer) uses this feature.