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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.
| 20.1 Introduction to Minibuffers | Basic information about minibuffers. | |
| 20.2 Reading Text Strings with the Minibuffer | How to read a straight text string. | |
| 20.3 Reading Lisp Objects with the Minibuffer | How to read a Lisp object or expression. | |
| 20.4 Minibuffer History | Recording previous minibuffer inputs so the user can reuse them. | |
| 20.5 Completion | How to invoke and customize completion. | |
| 20.6 Yes-or-No Queries | Asking a question with a simple answer. | |
| 20.7 Asking Multiple Y-or-N Questions | Asking a series of similar questions. | |
| 20.8 Reading a Password | Reading a password from the terminal. | |
| 20.9 Minibuffer Miscellany | Various customization hooks and variables. |
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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 29.8 Minibuffers and Frames.)
The text in the minibuffer always starts with the prompt string,
the text that was specified by the program that is using the minibuffer
to tell the user what sort of input to type. This text is marked
read-only so you won't accidentally delete or change it. It is also
marked as a field (see section 32.19.10 Defining and Using Fields), so that certain motion functions,
including beginning-of-line, forward-word,
forward-sentence, and forward-paragraph, stop at the
boundary between the prompt and the actual text. (In older Emacs
versions, the prompt was displayed using a special mechanism and was not
part of the buffer contents.)
The minibuffer's window is normally a single line; it grows automatically if necessary if the contents require more space. You can explicitly 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 20.9 Minibuffer Miscellany).
Like other buffers, a minibuffer may use any of several local keymaps (see section 22. Keymaps); these contain various exit commands and in some cases completion commands (see section 20.5 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.
When Emacs is running in batch mode, any request to read from the minibuffer actually reads a line from the standard input descriptor that was supplied when Emacs was started.
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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 21.2 Defining Commands.
nil, then it uses
read to convert the text into a Lisp object (see section 19.3 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 19.3 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 20.4 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 33.11 Input Methods) and
the setting of enable-multibyte-characters (see section 33.1 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-minibuffer
exit-minibuffer
abort-recursive-edit
next-history-element
previous-history-element
next-matching-history-element
previous-matching-history-element
read-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-minibuffer
exit-minibuffer
self-insert-and-exit
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This 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 19.5 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.
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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 specify startpos, then you should also specify that element of the history as the initial minibuffer contents, for consistency.
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).
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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.
| 20.5.1 Basic Completion Functions | Low-level functions for completing strings. | |
| (These are too low level to use the minibuffer.) | ||
|---|---|---|
| 20.5.2 Completion and the Minibuffer | Invoking the minibuffer with completion. | |
| 20.5.3 Minibuffer Commands that Do Completion | Minibuffer commands that do completion. | |
| 20.5.4 High-Level Completion Functions | Convenient special cases of completion | |
| (reading buffer name, file name, etc.) | ||
| 20.5.5 Reading File Names | Using completion to read file names. | |
| 20.5.6 Programmed Completion | Finding the completions for a given file name. | |
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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 5.8 Association Lists), the CARs of the alist elements form the set of permissible completions.
If collection is an obarray (see section 8.3 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 20.5.6 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 nospace is
non-nil, completions that start with a space are ignored unless
string also starts with a space.
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 20.5.6 Programmed Completion.
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.
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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 20.5.3 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 20.4 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.
We discourage use of a non-nil value for
initial, because it is an intrusive interface. The history
list feature (which did not exist when we introduced initial)
offers a far more convenient and general way for the user to get the
default and edit it, and it is always available.
If the argument inherit-input-method is non-nil, then the
minibuffer inherits the current input method (see section 33.11 Input Methods) and the setting of enable-multibyte-characters
(see section 33.1 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 20.5.1 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 20.5.3 Minibuffer Commands that Do Completion.
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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-help
minibuffer-complete-word
minibuffer-complete
with other characters bound as in minibuffer-local-map
(see section 20.2 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-help
minibuffer-complete-word
minibuffer-complete
minibuffer-complete-and-exit
minibuffer-complete-and-exit
with 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 35. 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 19. 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.
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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 21.2 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 21.3 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 33.10.4 User-Chosen Coding Systems.
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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 ---------- |
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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 25.8.6 File Name Completion.
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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 21.4 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 38.4 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 34.5 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 40.7 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 ---------- |
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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 34.5 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.
Normally, map-y-or-n-p binds cursor-in-echo-area while
prompting. But if no-cursor-in-echo-area is non-nil, it
does not do that.
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 21.4 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.
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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.
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This section describes some basic functions and variables related to minibuffers.
last-command-char;
see section 21.4 Information from the Command Loop).
nil.
minibuffer-contents, except that it does not copy text
properties, just the characters themselves. See section 32.19 Text Properties.
help-form
locally inside the minibuffer (see section 24.5 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 21.12 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.
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