2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, 2002,
4 @c 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../info/minibuf
7 @node Minibuffers, Command Loop, Read and Print, Top
9 @cindex arguments, reading
10 @cindex complex arguments
13 A @dfn{minibuffer} is a special buffer that Emacs commands use to
14 read arguments more complicated than the single numeric prefix
15 argument. These arguments include file names, buffer names, and
16 command names (as in @kbd{M-x}). The minibuffer is displayed on the
17 bottom line of the frame, in the same place as the echo area
18 (@pxref{The Echo Area}), but only while it is in use for reading an
22 * Intro to Minibuffers:: Basic information about minibuffers.
23 * Text from Minibuffer:: How to read a straight text string.
24 * Object from Minibuffer:: How to read a Lisp object or expression.
25 * Minibuffer History:: Recording previous minibuffer inputs
26 so the user can reuse them.
27 * Initial Input:: Specifying initial contents for the minibuffer.
28 * Completion:: How to invoke and customize completion.
29 * Yes-or-No Queries:: Asking a question with a simple answer.
30 * Multiple Queries:: Asking a series of similar questions.
31 * Reading a Password:: Reading a password from the terminal.
32 * Minibuffer Commands:: Commands used as key bindings in minibuffers.
33 * Minibuffer Contents:: How such commands access the minibuffer text.
34 * Minibuffer Windows:: Operating on the special minibuffer windows.
35 * Recursive Mini:: Whether recursive entry to minibuffer is allowed.
36 * Minibuffer Misc:: Various customization hooks and variables.
39 @node Intro to Minibuffers
40 @section Introduction to Minibuffers
42 In most ways, a minibuffer is a normal Emacs buffer. Most operations
43 @emph{within} a buffer, such as editing commands, work normally in a
44 minibuffer. However, many operations for managing buffers do not apply
45 to minibuffers. The name of a minibuffer always has the form @w{@samp{
46 *Minibuf-@var{number}*}}, and it cannot be changed. Minibuffers are
47 displayed only in special windows used only for minibuffers; these
48 windows always appear at the bottom of a frame. (Sometimes frames have
49 no minibuffer window, and sometimes a special kind of frame contains
50 nothing but a minibuffer window; see @ref{Minibuffers and Frames}.)
52 The text in the minibuffer always starts with the @dfn{prompt string},
53 the text that was specified by the program that is using the minibuffer
54 to tell the user what sort of input to type. This text is marked
55 read-only so you won't accidentally delete or change it. It is also
56 marked as a field (@pxref{Fields}), so that certain motion functions,
57 including @code{beginning-of-line}, @code{forward-word},
58 @code{forward-sentence}, and @code{forward-paragraph}, stop at the
59 boundary between the prompt and the actual text. (In older Emacs
60 versions, the prompt was displayed using a special mechanism and was not
61 part of the buffer contents.)
63 The minibuffer's window is normally a single line; it grows
64 automatically if necessary if the contents require more space. You can
65 explicitly resize it temporarily with the window sizing commands; it
66 reverts to its normal size when the minibuffer is exited. You can
67 resize it permanently by using the window sizing commands in the frame's
68 other window, when the minibuffer is not active. If the frame contains
69 just a minibuffer, you can change the minibuffer's size by changing the
72 Use of the minibuffer reads input events, and that alters the values
73 of variables such as @code{this-command} and @code{last-command}
74 (@pxref{Command Loop Info}). Your program should bind them around the
75 code that uses the minibuffer, if you do not want that to change them.
77 If a command uses a minibuffer while there is an active minibuffer,
78 this is called a @dfn{recursive minibuffer}. The first minibuffer is
79 named @w{@samp{ *Minibuf-0*}}. Recursive minibuffers are named by
80 incrementing the number at the end of the name. (The names begin with a
81 space so that they won't show up in normal buffer lists.) Of several
82 recursive minibuffers, the innermost (or most recently entered) is the
83 active minibuffer. We usually call this ``the'' minibuffer. You can
84 permit or forbid recursive minibuffers by setting the variable
85 @code{enable-recursive-minibuffers} or by putting properties of that
86 name on command symbols (@pxref{Recursive Mini}).
88 Like other buffers, a minibuffer uses a local keymap
89 (@pxref{Keymaps}) to specify special key bindings. The function that
90 invokes the minibuffer also sets up its local map according to the job
91 to be done. @xref{Text from Minibuffer}, for the non-completion
92 minibuffer local maps. @xref{Completion Commands}, for the minibuffer
93 local maps for completion.
95 When Emacs is running in batch mode, any request to read from the
96 minibuffer actually reads a line from the standard input descriptor that
97 was supplied when Emacs was started.
99 @node Text from Minibuffer
100 @section Reading Text Strings with the Minibuffer
102 Most often, the minibuffer is used to read text as a string. It can
103 also be used to read a Lisp object in textual form. The most basic
104 primitive for minibuffer input is @code{read-from-minibuffer}; it can do
105 either one. There are also specialized commands for reading
106 commands, variables, file names, etc. (@pxref{Completion}).
108 In most cases, you should not call minibuffer input functions in the
109 middle of a Lisp function. Instead, do all minibuffer input as part of
110 reading the arguments for a command, in the @code{interactive}
111 specification. @xref{Defining Commands}.
113 @defun read-from-minibuffer prompt-string &optional initial-contents keymap read hist default inherit-input-method keep-all
114 This function is the most general way to get input through the
115 minibuffer. By default, it accepts arbitrary text and returns it as a
116 string; however, if @var{read} is non-@code{nil}, then it uses
117 @code{read} to convert the text into a Lisp object (@pxref{Input
120 The first thing this function does is to activate a minibuffer and
121 display it with @var{prompt-string} as the prompt. This value must be a
122 string. Then the user can edit text in the minibuffer.
124 When the user types a command to exit the minibuffer,
125 @code{read-from-minibuffer} constructs the return value from the text in
126 the minibuffer. Normally it returns a string containing that text.
127 However, if @var{read} is non-@code{nil}, @code{read-from-minibuffer}
128 reads the text and returns the resulting Lisp object, unevaluated.
129 (@xref{Input Functions}, for information about reading.)
131 The argument @var{default} specifies a default value to make available
132 through the history commands. It should be a string, or @code{nil}.
133 If non-@code{nil}, the user can access it using
134 @code{next-history-element}, usually bound in the minibuffer to
135 @kbd{M-n}. If @var{read} is non-@code{nil}, then @var{default} is
136 also used as the input to @code{read}, if the user enters empty input.
137 (If @var{read} is non-@code{nil} and @var{default} is @code{nil}, empty
138 input results in an @code{end-of-file} error.) However, in the usual
139 case (where @var{read} is @code{nil}), @code{read-from-minibuffer}
140 ignores @var{default} when the user enters empty input and returns an
141 empty string, @code{""}. In this respect, it is different from all
142 the other minibuffer input functions in this chapter.
144 If @var{keymap} is non-@code{nil}, that keymap is the local keymap to
145 use in the minibuffer. If @var{keymap} is omitted or @code{nil}, the
146 value of @code{minibuffer-local-map} is used as the keymap. Specifying
147 a keymap is the most important way to customize the minibuffer for
148 various applications such as completion.
150 The argument @var{hist} specifies which history list variable to use
151 for saving the input and for history commands used in the minibuffer.
152 It defaults to @code{minibuffer-history}. @xref{Minibuffer History}.
154 If the variable @code{minibuffer-allow-text-properties} is
155 non-@code{nil}, then the string which is returned includes whatever text
156 properties were present in the minibuffer. Otherwise all the text
157 properties are stripped when the value is returned.
159 If the argument @var{inherit-input-method} is non-@code{nil}, then the
160 minibuffer inherits the current input method (@pxref{Input Methods}) and
161 the setting of @code{enable-multibyte-characters} (@pxref{Text
162 Representations}) from whichever buffer was current before entering the
165 If @var{keep-all} is non-@code{nil}, even empty and duplicate inputs
166 are added to the history list.
168 Use of @var{initial-contents} is mostly deprecated; we recommend using
169 a non-@code{nil} value only in conjunction with specifying a cons cell
170 for @var{hist}. @xref{Initial Input}.
173 @defun read-string prompt &optional initial history default inherit-input-method
174 This function reads a string from the minibuffer and returns it. The
175 arguments @var{prompt}, @var{initial}, @var{history} and
176 @var{inherit-input-method} are used as in @code{read-from-minibuffer}.
177 The keymap used is @code{minibuffer-local-map}.
179 The optional argument @var{default} is used as in
180 @code{read-from-minibuffer}, except that, if non-@code{nil}, it also
181 specifies a default value to return if the user enters null input. As
182 in @code{read-from-minibuffer} it should be a string, or @code{nil},
183 which is equivalent to an empty string.
185 This function is a simplified interface to the
186 @code{read-from-minibuffer} function:
190 (read-string @var{prompt} @var{initial} @var{history} @var{default} @var{inherit})
193 (read-from-minibuffer @var{prompt} @var{initial} nil nil
194 @var{history} @var{default} @var{inherit})))
195 (if (and (equal value "") @var{default})
202 @defvar minibuffer-allow-text-properties
203 If this variable is @code{nil}, then @code{read-from-minibuffer} strips
204 all text properties from the minibuffer input before returning it.
205 This variable also affects @code{read-string}. However,
206 @code{read-no-blanks-input} (see below), as well as
207 @code{read-minibuffer} and related functions (@pxref{Object from
208 Minibuffer,, Reading Lisp Objects With the Minibuffer}), and all
209 functions that do minibuffer input with completion, discard text
210 properties unconditionally, regardless of the value of this variable.
213 @defvar minibuffer-local-map
214 @anchor{Definition of minibuffer-local-map}
215 This is the default local keymap for reading from the minibuffer. By
216 default, it makes the following bindings:
220 @code{exit-minibuffer}
223 @code{exit-minibuffer}
226 @code{abort-recursive-edit}
230 @code{next-history-element}
234 @code{previous-history-element}
237 @code{next-matching-history-element}
240 @code{previous-matching-history-element}
244 @c In version 18, initial is required
246 @defun read-no-blanks-input prompt &optional initial inherit-input-method
247 This function reads a string from the minibuffer, but does not allow
248 whitespace characters as part of the input: instead, those characters
249 terminate the input. The arguments @var{prompt}, @var{initial}, and
250 @var{inherit-input-method} are used as in @code{read-from-minibuffer}.
252 This is a simplified interface to the @code{read-from-minibuffer}
253 function, and passes the value of the @code{minibuffer-local-ns-map}
254 keymap as the @var{keymap} argument for that function. Since the keymap
255 @code{minibuffer-local-ns-map} does not rebind @kbd{C-q}, it @emph{is}
256 possible to put a space into the string, by quoting it.
258 This function discards text properties, regardless of the value of
259 @code{minibuffer-allow-text-properties}.
263 (read-no-blanks-input @var{prompt} @var{initial})
265 (let (minibuffer-allow-text-properties)
266 (read-from-minibuffer @var{prompt} @var{initial} minibuffer-local-ns-map))
271 @defvar minibuffer-local-ns-map
272 This built-in variable is the keymap used as the minibuffer local keymap
273 in the function @code{read-no-blanks-input}. By default, it makes the
274 following bindings, in addition to those of @code{minibuffer-local-map}:
278 @cindex @key{SPC} in minibuffer
279 @code{exit-minibuffer}
282 @cindex @key{TAB} in minibuffer
283 @code{exit-minibuffer}
286 @cindex @kbd{?} in minibuffer
287 @code{self-insert-and-exit}
291 @node Object from Minibuffer
292 @section Reading Lisp Objects with the Minibuffer
294 This section describes functions for reading Lisp objects with the
297 @defun read-minibuffer prompt &optional initial
298 This function reads a Lisp object using the minibuffer, and returns it
299 without evaluating it. The arguments @var{prompt} and @var{initial} are
300 used as in @code{read-from-minibuffer}.
302 This is a simplified interface to the
303 @code{read-from-minibuffer} function:
307 (read-minibuffer @var{prompt} @var{initial})
309 (let (minibuffer-allow-text-properties)
310 (read-from-minibuffer @var{prompt} @var{initial} nil t))
314 Here is an example in which we supply the string @code{"(testing)"} as
320 "Enter an expression: " (format "%s" '(testing)))
322 ;; @r{Here is how the minibuffer is displayed:}
326 ---------- Buffer: Minibuffer ----------
327 Enter an expression: (testing)@point{}
328 ---------- Buffer: Minibuffer ----------
333 The user can type @key{RET} immediately to use the initial input as a
334 default, or can edit the input.
337 @defun eval-minibuffer prompt &optional initial
338 This function reads a Lisp expression using the minibuffer, evaluates
339 it, then returns the result. The arguments @var{prompt} and
340 @var{initial} are used as in @code{read-from-minibuffer}.
342 This function simply evaluates the result of a call to
343 @code{read-minibuffer}:
347 (eval-minibuffer @var{prompt} @var{initial})
349 (eval (read-minibuffer @var{prompt} @var{initial}))
354 @defun edit-and-eval-command prompt form
355 This function reads a Lisp expression in the minibuffer, and then
356 evaluates it. The difference between this command and
357 @code{eval-minibuffer} is that here the initial @var{form} is not
358 optional and it is treated as a Lisp object to be converted to printed
359 representation rather than as a string of text. It is printed with
360 @code{prin1}, so if it is a string, double-quote characters (@samp{"})
361 appear in the initial text. @xref{Output Functions}.
363 The first thing @code{edit-and-eval-command} does is to activate the
364 minibuffer with @var{prompt} as the prompt. Then it inserts the printed
365 representation of @var{form} in the minibuffer, and lets the user edit it.
366 When the user exits the minibuffer, the edited text is read with
367 @code{read} and then evaluated. The resulting value becomes the value
368 of @code{edit-and-eval-command}.
370 In the following example, we offer the user an expression with initial
371 text which is a valid form already:
375 (edit-and-eval-command "Please edit: " '(forward-word 1))
377 ;; @r{After evaluation of the preceding expression,}
378 ;; @r{the following appears in the minibuffer:}
382 ---------- Buffer: Minibuffer ----------
383 Please edit: (forward-word 1)@point{}
384 ---------- Buffer: Minibuffer ----------
389 Typing @key{RET} right away would exit the minibuffer and evaluate the
390 expression, thus moving point forward one word.
391 @code{edit-and-eval-command} returns @code{nil} in this example.
394 @node Minibuffer History
395 @section Minibuffer History
396 @cindex minibuffer history
399 A @dfn{minibuffer history list} records previous minibuffer inputs so
400 the user can reuse them conveniently. A history list is actually a
401 symbol, not a list; it is a variable whose value is a list of strings
402 (previous inputs), most recent first.
404 There are many separate history lists, used for different kinds of
405 inputs. It's the Lisp programmer's job to specify the right history
406 list for each use of the minibuffer.
408 You specify the history list with the optional @var{hist} argument
409 to either @code{read-from-minibuffer} or @code{completing-read}. Here
410 are the possible values for it:
414 Use @var{variable} (a symbol) as the history list.
416 @item (@var{variable} . @var{startpos})
417 Use @var{variable} (a symbol) as the history list, and assume that the
418 initial history position is @var{startpos} (a nonnegative integer).
420 Specifying 0 for @var{startpos} is equivalent to just specifying the
421 symbol @var{variable}. @code{previous-history-element} will display
422 the most recent element of the history list in the minibuffer. If you
423 specify a positive @var{startpos}, the minibuffer history functions
424 behave as if @code{(elt @var{variable} (1- @var{STARTPOS}))} were the
425 history element currently shown in the minibuffer.
427 For consistency, you should also specify that element of the history
428 as the initial minibuffer contents, using the @var{initial} argument
429 to the minibuffer input function (@pxref{Initial Input}).
432 If you don't specify @var{hist}, then the default history list
433 @code{minibuffer-history} is used. For other standard history lists,
434 see below. You can also create your own history list variable; just
435 initialize it to @code{nil} before the first use.
437 Both @code{read-from-minibuffer} and @code{completing-read} add new
438 elements to the history list automatically, and provide commands to
439 allow the user to reuse items on the list. The only thing your program
440 needs to do to use a history list is to initialize it and to pass its
441 name to the input functions when you wish. But it is safe to modify the
442 list by hand when the minibuffer input functions are not using it.
444 Emacs functions that add a new element to a history list can also
445 delete old elements if the list gets too long. The variable
446 @code{history-length} specifies the maximum length for most history
447 lists. To specify a different maximum length for a particular history
448 list, put the length in the @code{history-length} property of the
449 history list symbol. The variable @code{history-delete-duplicates}
450 specifies whether to delete duplicates in history.
452 @defun add-to-history history-var newelt &optional maxelt keep-all
453 This function adds a new element @var{newelt}, if non-empty, to the
454 history list stored in the variable @var{history-var}, and returns the
455 updated history list. By default, the list length is limited by the
456 value specified by @code{history-length} (described below), but the
457 optional argument @var{maxelt} overrides that. The possible values of
458 @var{maxelt} have the same meaning as the values of
459 @code{history-length}.
461 Duplicate members are removed from the history list, if
462 @code{history-delete-duplicates} is non-@code{nil}.
464 If @var{keep-all} is non-@code{nil}, even an empty or duplicate
465 @var{newelt} element is added to the history list.
468 @defvar history-length
469 The value of this variable specifies the maximum length for all
470 history lists that don't specify their own maximum lengths. If the
471 value is @code{t}, that means there no maximum (don't delete old
472 elements). The value of @code{history-length} property of the history
473 list variable's symbol, if set, overrides this variable for that
474 particular history list.
477 @defvar history-delete-duplicates
478 If the value of this variable is @code{t}, that means when adding a
479 new history element, all previous identical elements are deleted.
482 Here are some of the standard minibuffer history list variables:
484 @defvar minibuffer-history
485 The default history list for minibuffer history input.
488 @defvar query-replace-history
489 A history list for arguments to @code{query-replace} (and similar
490 arguments to other commands).
493 @defvar file-name-history
494 A history list for file-name arguments.
497 @defvar buffer-name-history
498 A history list for buffer-name arguments.
501 @defvar regexp-history
502 A history list for regular expression arguments.
505 @defvar extended-command-history
506 A history list for arguments that are names of extended commands.
509 @defvar shell-command-history
510 A history list for arguments that are shell commands.
513 @defvar read-expression-history
514 A history list for arguments that are Lisp expressions to evaluate.
518 @section Initial Input
520 Several of the functions for minibuffer input have an argument called
521 @var{initial} or @var{initial-contents}. This is a mostly-deprecated
522 feature for specifying that the minibuffer should start out with
523 certain text, instead of empty as usual.
525 If @var{initial} is a string, the minibuffer starts out containing the
526 text of the string, with point at the end, when the user starts to
527 edit the text. If the user simply types @key{RET} to exit the
528 minibuffer, it will use the initial input string to determine the
531 @strong{We discourage use of a non-@code{nil} value for
532 @var{initial}}, because initial input is an intrusive interface.
533 History lists and default values provide a much more convenient method
534 to offer useful default inputs to the user.
536 There is just one situation where you should specify a string for an
537 @var{initial} argument. This is when you specify a cons cell for the
538 @var{hist} or @var{history} argument. @xref{Minibuffer History}.
540 @var{initial} can also be a cons cell of the form @code{(@var{string}
541 . @var{position})}. This means to insert @var{string} in the
542 minibuffer but put point at @var{position} within the string's text.
544 As a historical accident, @var{position} was implemented
545 inconsistently in different functions. In @code{completing-read},
546 @var{position}'s value is interpreted as origin-zero; that is, a value
547 of 0 means the beginning of the string, 1 means after the first
548 character, etc. In @code{read-minibuffer}, and the other
549 non-completion minibuffer input functions that support this argument,
550 1 means the beginning of the string 2 means after the first character,
553 Use of a cons cell as the value for @var{initial} arguments is
554 deprecated in user code.
560 @dfn{Completion} is a feature that fills in the rest of a name
561 starting from an abbreviation for it. Completion works by comparing the
562 user's input against a list of valid names and determining how much of
563 the name is determined uniquely by what the user has typed. For
564 example, when you type @kbd{C-x b} (@code{switch-to-buffer}) and then
565 type the first few letters of the name of the buffer to which you wish
566 to switch, and then type @key{TAB} (@code{minibuffer-complete}), Emacs
567 extends the name as far as it can.
569 Standard Emacs commands offer completion for names of symbols, files,
570 buffers, and processes; with the functions in this section, you can
571 implement completion for other kinds of names.
573 The @code{try-completion} function is the basic primitive for
574 completion: it returns the longest determined completion of a given
575 initial string, with a given set of strings to match against.
577 The function @code{completing-read} provides a higher-level interface
578 for completion. A call to @code{completing-read} specifies how to
579 determine the list of valid names. The function then activates the
580 minibuffer with a local keymap that binds a few keys to commands useful
581 for completion. Other functions provide convenient simple interfaces
582 for reading certain kinds of names with completion.
585 * Basic Completion:: Low-level functions for completing strings.
586 (These are too low level to use the minibuffer.)
587 * Minibuffer Completion:: Invoking the minibuffer with completion.
588 * Completion Commands:: Minibuffer commands that do completion.
589 * High-Level Completion:: Convenient special cases of completion
590 (reading buffer name, file name, etc.)
591 * Reading File Names:: Using completion to read file names.
592 * Programmed Completion:: Writing your own completion-function.
595 @node Basic Completion
596 @subsection Basic Completion Functions
598 The completion functions @code{try-completion},
599 @code{all-completions} and @code{test-completion} have nothing in
600 themselves to do with minibuffers. We describe them in this chapter
601 so as to keep them near the higher-level completion features that do
604 If you store a completion alist in a variable, you should mark the
605 variable as ``risky'' with a non-@code{nil}
606 @code{risky-local-variable} property.
608 @defun try-completion string collection &optional predicate
609 This function returns the longest common substring of all possible
610 completions of @var{string} in @var{collection}. The value of
611 @var{collection} must be a list of strings or symbols, an alist, an
612 obarray, a hash table, or a function that implements a virtual set of
615 Completion compares @var{string} against each of the permissible
616 completions specified by @var{collection}; if the beginning of the
617 permissible completion equals @var{string}, it matches. If no permissible
618 completions match, @code{try-completion} returns @code{nil}. If only
619 one permissible completion matches, and the match is exact, then
620 @code{try-completion} returns @code{t}. Otherwise, the value is the
621 longest initial sequence common to all the permissible completions that
624 If @var{collection} is an alist (@pxref{Association Lists}), the
625 permissible completions are the elements of the alist that are either
626 strings, symbols, or conses whose @sc{car} is a string or symbol.
627 Symbols are converted to strings using @code{symbol-name}.
628 Other elements of the alist are ignored. (Remember that in Emacs Lisp,
629 the elements of alists do not @emph{have} to be conses.) As all
630 elements of the alist can be strings, this case actually includes
631 lists of strings or symbols, even though we usually do not think of
632 such lists as alists.
634 @cindex obarray in completion
635 If @var{collection} is an obarray (@pxref{Creating Symbols}), the names
636 of all symbols in the obarray form the set of permissible completions. The
637 global variable @code{obarray} holds an obarray containing the names of
638 all interned Lisp symbols.
640 Note that the only valid way to make a new obarray is to create it
641 empty and then add symbols to it one by one using @code{intern}.
642 Also, you cannot intern a given symbol in more than one obarray.
644 If @var{collection} is a hash table, then the keys that are strings
645 are the possible completions. Other keys are ignored.
647 You can also use a symbol that is a function as @var{collection}. Then
648 the function is solely responsible for performing completion;
649 @code{try-completion} returns whatever this function returns. The
650 function is called with three arguments: @var{string}, @var{predicate}
651 and @code{nil}. (The reason for the third argument is so that the same
652 function can be used in @code{all-completions} and do the appropriate
653 thing in either case.) @xref{Programmed Completion}.
655 If the argument @var{predicate} is non-@code{nil}, then it must be a
656 function of one argument, unless @var{collection} is a hash table, in
657 which case it should be a function of two arguments. It is used to
658 test each possible match, and the match is accepted only if
659 @var{predicate} returns non-@code{nil}. The argument given to
660 @var{predicate} is either a string or a cons cell (the @sc{car} of
661 which is a string) from the alist, or a symbol (@emph{not} a symbol
662 name) from the obarray. If @var{collection} is a hash table,
663 @var{predicate} is called with two arguments, the string key and the
666 In addition, to be acceptable, a completion must also match all the
667 regular expressions in @code{completion-regexp-list}. (Unless
668 @var{collection} is a function, in which case that function has to
669 handle @code{completion-regexp-list} itself.)
671 In the first of the following examples, the string @samp{foo} is
672 matched by three of the alist @sc{car}s. All of the matches begin with
673 the characters @samp{fooba}, so that is the result. In the second
674 example, there is only one possible match, and it is exact, so the value
681 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)))
686 (try-completion "foo" '(("barfoo" 2) ("foo" 3)))
691 In the following example, numerous symbols begin with the characters
692 @samp{forw}, and all of them begin with the word @samp{forward}. In
693 most of the symbols, this is followed with a @samp{-}, but not in all,
694 so no more than @samp{forward} can be completed.
698 (try-completion "forw" obarray)
703 Finally, in the following example, only two of the three possible
704 matches pass the predicate @code{test} (the string @samp{foobaz} is
705 too short). Both of those begin with the string @samp{foobar}.
710 (> (length (car s)) 6))
716 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
723 @defun all-completions string collection &optional predicate nospace
724 This function returns a list of all possible completions of
725 @var{string}. The arguments to this function (aside from
726 @var{nospace}) are the same as those of @code{try-completion}. Also,
727 this function uses @code{completion-regexp-list} in the same way that
728 @code{try-completion} does. The optional argument @var{nospace} only
729 matters if @var{string} is the empty string. In that case, if
730 @var{nospace} is non-@code{nil}, completions that start with a space
733 If @var{collection} is a function, it is called with three arguments:
734 @var{string}, @var{predicate} and @code{t}; then @code{all-completions}
735 returns whatever the function returns. @xref{Programmed Completion}.
737 Here is an example, using the function @code{test} shown in the
738 example for @code{try-completion}:
743 (> (length (car s)) 6))
750 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
752 @result{} ("foobar1" "foobar2")
757 @defun test-completion string collection &optional predicate
758 @anchor{Definition of test-completion}
759 This function returns non-@code{nil} if @var{string} is a valid
760 completion possibility specified by @var{collection} and
761 @var{predicate}. The arguments are the same as in
762 @code{try-completion}. For instance, if @var{collection} is a list of
763 strings, this is true if @var{string} appears in the list and
764 @var{predicate} is satisfied.
766 @code{test-completion} uses @code{completion-regexp-list} in the same
767 way that @code{try-completion} does.
769 If @var{predicate} is non-@code{nil} and if @var{collection} contains
770 several strings that are equal to each other, as determined by
771 @code{compare-strings} according to @code{completion-ignore-case},
772 then @var{predicate} should accept either all or none of them.
773 Otherwise, the return value of @code{test-completion} is essentially
776 If @var{collection} is a function, it is called with three arguments,
777 the values @var{string}, @var{predicate} and @code{lambda}; whatever
778 it returns, @code{test-completion} returns in turn.
781 @defvar completion-ignore-case
782 If the value of this variable is non-@code{nil}, Emacs does not
783 consider case significant in completion.
786 @defvar completion-regexp-list
787 This is a list of regular expressions. The completion functions only
788 consider a completion acceptable if it matches all regular expressions
789 in this list, with @code{case-fold-search} (@pxref{Searching and Case})
790 bound to the value of @code{completion-ignore-case}.
793 @defmac lazy-completion-table var fun
794 This macro provides a way to initialize the variable @var{var} as a
795 collection for completion in a lazy way, not computing its actual
796 contents until they are first needed. You use this macro to produce a
797 value that you store in @var{var}. The actual computation of the
798 proper value is done the first time you do completion using @var{var}.
799 It is done by calling @var{fun} with no arguments. The
800 value @var{fun} returns becomes the permanent value of @var{var}.
802 Here is an example of use:
805 (defvar foo (lazy-completion-table foo make-my-alist))
809 @node Minibuffer Completion
810 @subsection Completion and the Minibuffer
812 This section describes the basic interface for reading from the
813 minibuffer with completion.
815 @defun completing-read prompt collection &optional predicate require-match initial hist default inherit-input-method
816 This function reads a string in the minibuffer, assisting the user by
817 providing completion. It activates the minibuffer with prompt
818 @var{prompt}, which must be a string.
820 The actual completion is done by passing @var{collection} and
821 @var{predicate} to the function @code{try-completion}. This happens
822 in certain commands bound in the local keymaps used for completion.
823 Some of these commands also call @code{test-completion}. Thus, if
824 @var{predicate} is non-@code{nil}, it should be compatible with
825 @var{collection} and @code{completion-ignore-case}. @xref{Definition
828 If @var{require-match} is @code{nil}, the exit commands work regardless
829 of the input in the minibuffer. If @var{require-match} is @code{t}, the
830 usual minibuffer exit commands won't exit unless the input completes to
831 an element of @var{collection}. If @var{require-match} is neither
832 @code{nil} nor @code{t}, then the exit commands won't exit unless the
833 input already in the buffer matches an element of @var{collection}.
835 However, empty input is always permitted, regardless of the value of
836 @var{require-match}; in that case, @code{completing-read} returns
837 @var{default}, or @code{""}, if @var{default} is @code{nil}. The
838 value of @var{default} (if non-@code{nil}) is also available to the
839 user through the history commands.
841 The function @code{completing-read} uses
842 @code{minibuffer-local-completion-map} as the keymap if
843 @var{require-match} is @code{nil}, and uses
844 @code{minibuffer-local-must-match-map} if @var{require-match} is
845 non-@code{nil}. @xref{Completion Commands}.
847 The argument @var{hist} specifies which history list variable to use for
848 saving the input and for minibuffer history commands. It defaults to
849 @code{minibuffer-history}. @xref{Minibuffer History}.
851 The argument @var{initial} is mostly deprecated; we recommend using a
852 non-@code{nil} value only in conjunction with specifying a cons cell
853 for @var{hist}. @xref{Initial Input}. For default input, use
854 @var{default} instead.
856 If the argument @var{inherit-input-method} is non-@code{nil}, then the
857 minibuffer inherits the current input method (@pxref{Input
858 Methods}) and the setting of @code{enable-multibyte-characters}
859 (@pxref{Text Representations}) from whichever buffer was current before
860 entering the minibuffer.
862 If the built-in variable @code{completion-ignore-case} is
863 non-@code{nil}, completion ignores case when comparing the input
864 against the possible matches. @xref{Basic Completion}. In this mode
865 of operation, @var{predicate} must also ignore case, or you will get
868 Here's an example of using @code{completing-read}:
874 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
879 ;; @r{After evaluation of the preceding expression,}
880 ;; @r{the following appears in the minibuffer:}
882 ---------- Buffer: Minibuffer ----------
883 Complete a foo: fo@point{}
884 ---------- Buffer: Minibuffer ----------
889 If the user then types @kbd{@key{DEL} @key{DEL} b @key{RET}},
890 @code{completing-read} returns @code{barfoo}.
892 The @code{completing-read} function binds variables to pass
893 information to the commands that actually do completion.
894 They are described in the following section.
897 @node Completion Commands
898 @subsection Minibuffer Commands that Do Completion
900 This section describes the keymaps, commands and user options used
901 in the minibuffer to do completion. The description refers to the
902 situation when Partial Completion mode is disabled (as it is by
903 default). When enabled, this minor mode uses its own alternatives to
904 some of the commands described below. @xref{Completion Options,,,
905 emacs, The GNU Emacs Manual}, for a short description of Partial
908 @defvar minibuffer-completion-table
909 The value of this variable is the collection used for completion in
910 the minibuffer. This is the global variable that contains what
911 @code{completing-read} passes to @code{try-completion}. It is used by
912 minibuffer completion commands such as @code{minibuffer-complete-word}.
915 @defvar minibuffer-completion-predicate
916 This variable's value is the predicate that @code{completing-read}
917 passes to @code{try-completion}. The variable is also used by the other
918 minibuffer completion functions.
921 @defvar minibuffer-completion-confirm
922 When the value of this variable is non-@code{nil}, Emacs asks for
923 confirmation of a completion before exiting the minibuffer.
924 @code{completing-read} binds this variable, and the function
925 @code{minibuffer-complete-and-exit} checks the value before exiting.
928 @deffn Command minibuffer-complete-word
929 This function completes the minibuffer contents by at most a single
930 word. Even if the minibuffer contents have only one completion,
931 @code{minibuffer-complete-word} does not add any characters beyond the
932 first character that is not a word constituent. @xref{Syntax Tables}.
935 @deffn Command minibuffer-complete
936 This function completes the minibuffer contents as far as possible.
939 @deffn Command minibuffer-complete-and-exit
940 This function completes the minibuffer contents, and exits if
941 confirmation is not required, i.e., if
942 @code{minibuffer-completion-confirm} is @code{nil}. If confirmation
943 @emph{is} required, it is given by repeating this command
944 immediately---the command is programmed to work without confirmation
945 when run twice in succession.
948 @deffn Command minibuffer-completion-help
949 This function creates a list of the possible completions of the
950 current minibuffer contents. It works by calling @code{all-completions}
951 using the value of the variable @code{minibuffer-completion-table} as
952 the @var{collection} argument, and the value of
953 @code{minibuffer-completion-predicate} as the @var{predicate} argument.
954 The list of completions is displayed as text in a buffer named
955 @samp{*Completions*}.
958 @defun display-completion-list completions &optional common-substring
959 This function displays @var{completions} to the stream in
960 @code{standard-output}, usually a buffer. (@xref{Read and Print}, for more
961 information about streams.) The argument @var{completions} is normally
962 a list of completions just returned by @code{all-completions}, but it
963 does not have to be. Each element may be a symbol or a string, either
964 of which is simply printed. It can also be a list of two strings,
965 which is printed as if the strings were concatenated. The first of
966 the two strings is the actual completion, the second string serves as
969 The argument @var{common-substring} is the prefix that is common to
970 all the completions. With normal Emacs completion, it is usually the
971 same as the string that was completed. @code{display-completion-list}
972 uses this to highlight text in the completion list for better visual
973 feedback. This is not needed in the minibuffer; for minibuffer
974 completion, you can pass @code{nil}.
976 This function is called by @code{minibuffer-completion-help}. The
977 most common way to use it is together with
978 @code{with-output-to-temp-buffer}, like this:
981 (with-output-to-temp-buffer "*Completions*"
982 (display-completion-list
983 (all-completions (buffer-string) my-alist)
988 @defopt completion-auto-help
989 If this variable is non-@code{nil}, the completion commands
990 automatically display a list of possible completions whenever nothing
991 can be completed because the next character is not uniquely determined.
994 @defvar minibuffer-local-completion-map
995 @code{completing-read} uses this value as the local keymap when an
996 exact match of one of the completions is not required. By default, this
997 keymap makes the following bindings:
1001 @code{minibuffer-completion-help}
1004 @code{minibuffer-complete-word}
1007 @code{minibuffer-complete}
1011 with other characters bound as in @code{minibuffer-local-map}
1012 (@pxref{Definition of minibuffer-local-map}).
1015 @defvar minibuffer-local-must-match-map
1016 @code{completing-read} uses this value as the local keymap when an
1017 exact match of one of the completions is required. Therefore, no keys
1018 are bound to @code{exit-minibuffer}, the command that exits the
1019 minibuffer unconditionally. By default, this keymap makes the following
1024 @code{minibuffer-completion-help}
1027 @code{minibuffer-complete-word}
1030 @code{minibuffer-complete}
1033 @code{minibuffer-complete-and-exit}
1036 @code{minibuffer-complete-and-exit}
1040 with other characters bound as in @code{minibuffer-local-map}.
1043 @defvar minibuffer-local-filename-completion-map
1044 This is like @code{minibuffer-local-completion-map}
1045 except that it does not bind @key{SPC}. This keymap is used by the
1046 function @code{read-file-name}.
1049 @defvar minibuffer-local-must-match-filename-map
1050 This is like @code{minibuffer-local-must-match-map}
1051 except that it does not bind @key{SPC}. This keymap is used by the
1052 function @code{read-file-name}.
1055 @node High-Level Completion
1056 @subsection High-Level Completion Functions
1058 This section describes the higher-level convenient functions for
1059 reading certain sorts of names with completion.
1061 In most cases, you should not call these functions in the middle of a
1062 Lisp function. When possible, do all minibuffer input as part of
1063 reading the arguments for a command, in the @code{interactive}
1064 specification. @xref{Defining Commands}.
1066 @defun read-buffer prompt &optional default existing
1067 This function reads the name of a buffer and returns it as a string.
1068 The argument @var{default} is the default name to use, the value to
1069 return if the user exits with an empty minibuffer. If non-@code{nil},
1070 it should be a string or a buffer. It is mentioned in the prompt, but
1071 is not inserted in the minibuffer as initial input.
1073 The argument @var{prompt} should be a string ending with a colon and a
1074 space. If @var{default} is non-@code{nil}, the function inserts it in
1075 @var{prompt} before the colon to follow the convention for reading from
1076 the minibuffer with a default value (@pxref{Programming Tips}).
1078 If @var{existing} is non-@code{nil}, then the name specified must be
1079 that of an existing buffer. The usual commands to exit the minibuffer
1080 do not exit if the text is not valid, and @key{RET} does completion to
1081 attempt to find a valid name. If @var{existing} is neither @code{nil}
1082 nor @code{t}, confirmation is required after completion. (However,
1083 @var{default} is not checked for validity; it is returned, whatever it
1084 is, if the user exits with the minibuffer empty.)
1086 In the following example, the user enters @samp{minibuffer.t}, and
1087 then types @key{RET}. The argument @var{existing} is @code{t}, and the
1088 only buffer name starting with the given input is
1089 @samp{minibuffer.texi}, so that name is the value.
1092 (read-buffer "Buffer name: " "foo" t)
1094 ;; @r{After evaluation of the preceding expression,}
1095 ;; @r{the following prompt appears,}
1096 ;; @r{with an empty minibuffer:}
1100 ---------- Buffer: Minibuffer ----------
1101 Buffer name (default foo): @point{}
1102 ---------- Buffer: Minibuffer ----------
1106 ;; @r{The user types @kbd{minibuffer.t @key{RET}}.}
1107 @result{} "minibuffer.texi"
1112 @defvar read-buffer-function
1113 This variable specifies how to read buffer names. For example, if you
1114 set this variable to @code{iswitchb-read-buffer}, all Emacs commands
1115 that call @code{read-buffer} to read a buffer name will actually use the
1116 @code{iswitchb} package to read it.
1119 @defun read-command prompt &optional default
1120 This function reads the name of a command and returns it as a Lisp
1121 symbol. The argument @var{prompt} is used as in
1122 @code{read-from-minibuffer}. Recall that a command is anything for
1123 which @code{commandp} returns @code{t}, and a command name is a symbol
1124 for which @code{commandp} returns @code{t}. @xref{Interactive Call}.
1126 The argument @var{default} specifies what to return if the user enters
1127 null input. It can be a symbol or a string; if it is a string,
1128 @code{read-command} interns it before returning it. If @var{default} is
1129 @code{nil}, that means no default has been specified; then if the user
1130 enters null input, the return value is @code{(intern "")}, that is, a
1131 symbol whose name is an empty string.
1134 (read-command "Command name? ")
1137 ;; @r{After evaluation of the preceding expression,}
1138 ;; @r{the following prompt appears with an empty minibuffer:}
1142 ---------- Buffer: Minibuffer ----------
1144 ---------- Buffer: Minibuffer ----------
1149 If the user types @kbd{forward-c @key{RET}}, then this function returns
1150 @code{forward-char}.
1152 The @code{read-command} function is a simplified interface to
1153 @code{completing-read}. It uses the variable @code{obarray} so as to
1154 complete in the set of extant Lisp symbols, and it uses the
1155 @code{commandp} predicate so as to accept only command names:
1157 @cindex @code{commandp} example
1160 (read-command @var{prompt})
1162 (intern (completing-read @var{prompt} obarray
1168 @defun read-variable prompt &optional default
1169 @anchor{Definition of read-variable}
1170 This function reads the name of a user variable and returns it as a
1173 The argument @var{default} specifies what to return if the user enters
1174 null input. It can be a symbol or a string; if it is a string,
1175 @code{read-variable} interns it before returning it. If @var{default}
1176 is @code{nil}, that means no default has been specified; then if the
1177 user enters null input, the return value is @code{(intern "")}.
1181 (read-variable "Variable name? ")
1183 ;; @r{After evaluation of the preceding expression,}
1184 ;; @r{the following prompt appears,}
1185 ;; @r{with an empty minibuffer:}
1189 ---------- Buffer: Minibuffer ----------
1190 Variable name? @point{}
1191 ---------- Buffer: Minibuffer ----------
1196 If the user then types @kbd{fill-p @key{RET}}, @code{read-variable}
1197 returns @code{fill-prefix}.
1199 This function is similar to @code{read-command}, but uses the
1200 predicate @code{user-variable-p} instead of @code{commandp}:
1202 @cindex @code{user-variable-p} example
1205 (read-variable @var{prompt})
1208 (completing-read @var{prompt} obarray
1209 'user-variable-p t nil))
1214 See also the functions @code{read-coding-system} and
1215 @code{read-non-nil-coding-system}, in @ref{User-Chosen Coding Systems},
1216 and @code{read-input-method-name}, in @ref{Input Methods}.
1218 @node Reading File Names
1219 @subsection Reading File Names
1221 Here is another high-level completion function, designed for reading a
1222 file name. It provides special features including automatic insertion
1223 of the default directory.
1225 @defun read-file-name prompt &optional directory default existing initial predicate
1226 This function reads a file name in the minibuffer, prompting with
1227 @var{prompt} and providing completion.
1229 If @var{existing} is non-@code{nil}, then the user must specify the name
1230 of an existing file; @key{RET} performs completion to make the name
1231 valid if possible, and then refuses to exit if it is not valid. If the
1232 value of @var{existing} is neither @code{nil} nor @code{t}, then
1233 @key{RET} also requires confirmation after completion. If
1234 @var{existing} is @code{nil}, then the name of a nonexistent file is
1237 The function @code{read-file-name} uses
1238 @code{minibuffer-local-filename-completion-map} as the keymap if
1239 @var{existing} is @code{nil}, and uses
1240 @code{minibuffer-local-must-match-filename-map} if @var{existing} is
1241 non-@code{nil}. @xref{Completion Commands}.
1243 The argument @var{directory} specifies the directory to use for
1244 completion of relative file names. It should be an absolute directory
1245 name. If @code{insert-default-directory} is non-@code{nil},
1246 @var{directory} is also inserted in the minibuffer as initial input.
1247 It defaults to the current buffer's value of @code{default-directory}.
1250 If you specify @var{initial}, that is an initial file name to insert
1251 in the buffer (after @var{directory}, if that is inserted). In this
1252 case, point goes at the beginning of @var{initial}. The default for
1253 @var{initial} is @code{nil}---don't insert any file name. To see what
1254 @var{initial} does, try the command @kbd{C-x C-v}. @strong{Please
1255 note:} we recommend using @var{default} rather than @var{initial} in
1258 If @var{default} is non-@code{nil}, then the function returns
1259 @var{default} if the user exits the minibuffer with the same non-empty
1260 contents that @code{read-file-name} inserted initially. The initial
1261 minibuffer contents are always non-empty if
1262 @code{insert-default-directory} is non-@code{nil}, as it is by
1263 default. @var{default} is not checked for validity, regardless of the
1264 value of @var{existing}. However, if @var{existing} is
1265 non-@code{nil}, the initial minibuffer contents should be a valid file
1266 (or directory) name. Otherwise @code{read-file-name} attempts
1267 completion if the user exits without any editing, and does not return
1268 @var{default}. @var{default} is also available through the history
1271 If @var{default} is @code{nil}, @code{read-file-name} tries to find a
1272 substitute default to use in its place, which it treats in exactly the
1273 same way as if it had been specified explicitly. If @var{default} is
1274 @code{nil}, but @var{initial} is non-@code{nil}, then the default is
1275 the absolute file name obtained from @var{directory} and
1276 @var{initial}. If both @var{default} and @var{initial} are @code{nil}
1277 and the buffer is visiting a file, @code{read-file-name} uses the
1278 absolute file name of that file as default. If the buffer is not
1279 visiting a file, then there is no default. In that case, if the user
1280 types @key{RET} without any editing, @code{read-file-name} simply
1281 returns the pre-inserted contents of the minibuffer.
1283 If the user types @key{RET} in an empty minibuffer, this function
1284 returns an empty string, regardless of the value of @var{existing}.
1285 This is, for instance, how the user can make the current buffer visit
1286 no file using @code{M-x set-visited-file-name}.
1288 If @var{predicate} is non-@code{nil}, it specifies a function of one
1289 argument that decides which file names are acceptable completion
1290 possibilities. A file name is an acceptable value if @var{predicate}
1291 returns non-@code{nil} for it.
1293 @code{read-file-name} does not automatically expand file names. You
1294 must call @code{expand-file-name} yourself if an absolute file name is
1301 (read-file-name "The file is ")
1303 ;; @r{After evaluation of the preceding expression,}
1304 ;; @r{the following appears in the minibuffer:}
1308 ---------- Buffer: Minibuffer ----------
1309 The file is /gp/gnu/elisp/@point{}
1310 ---------- Buffer: Minibuffer ----------
1315 Typing @kbd{manual @key{TAB}} results in the following:
1319 ---------- Buffer: Minibuffer ----------
1320 The file is /gp/gnu/elisp/manual.texi@point{}
1321 ---------- Buffer: Minibuffer ----------
1325 @c Wordy to avoid overfull hbox in smallbook mode.
1327 If the user types @key{RET}, @code{read-file-name} returns the file name
1328 as the string @code{"/gp/gnu/elisp/manual.texi"}.
1331 @defvar read-file-name-function
1332 If non-@code{nil}, this should be a function that accepts the same
1333 arguments as @code{read-file-name}. When @code{read-file-name} is
1334 called, it calls this function with the supplied arguments instead of
1335 doing its usual work.
1338 @defvar read-file-name-completion-ignore-case
1339 If this variable is non-@code{nil}, @code{read-file-name} ignores case
1340 when performing completion.
1343 @defun read-directory-name prompt &optional directory default existing initial
1344 This function is like @code{read-file-name} but allows only directory
1345 names as completion possibilities.
1347 If @var{default} is @code{nil} and @var{initial} is non-@code{nil},
1348 @code{read-directory-name} constructs a substitute default by
1349 combining @var{directory} (or the current buffer's default directory
1350 if @var{directory} is @code{nil}) and @var{initial}. If both
1351 @var{default} and @var{initial} are @code{nil}, this function uses
1352 @var{directory} as substitute default, or the current buffer's default
1353 directory if @var{directory} is @code{nil}.
1356 @defopt insert-default-directory
1357 This variable is used by @code{read-file-name}, and thus, indirectly,
1358 by most commands reading file names. (This includes all commands that
1359 use the code letters @samp{f} or @samp{F} in their interactive form.
1360 @xref{Interactive Codes,, Code Characters for interactive}.) Its
1361 value controls whether @code{read-file-name} starts by placing the
1362 name of the default directory in the minibuffer, plus the initial file
1363 name if any. If the value of this variable is @code{nil}, then
1364 @code{read-file-name} does not place any initial input in the
1365 minibuffer (unless you specify initial input with the @var{initial}
1366 argument). In that case, the default directory is still used for
1367 completion of relative file names, but is not displayed.
1369 If this variable is @code{nil} and the initial minibuffer contents are
1370 empty, the user may have to explicitly fetch the next history element
1371 to access a default value. If the variable is non-@code{nil}, the
1372 initial minibuffer contents are always non-empty and the user can
1373 always request a default value by immediately typing @key{RET} in an
1374 unedited minibuffer. (See above.)
1380 ;; @r{Here the minibuffer starts out with the default directory.}
1381 (let ((insert-default-directory t))
1382 (read-file-name "The file is "))
1386 ---------- Buffer: Minibuffer ----------
1387 The file is ~lewis/manual/@point{}
1388 ---------- Buffer: Minibuffer ----------
1392 ;; @r{Here the minibuffer is empty and only the prompt}
1393 ;; @r{appears on its line.}
1394 (let ((insert-default-directory nil))
1395 (read-file-name "The file is "))
1399 ---------- Buffer: Minibuffer ----------
1400 The file is @point{}
1401 ---------- Buffer: Minibuffer ----------
1406 @node Programmed Completion
1407 @subsection Programmed Completion
1408 @cindex programmed completion
1410 Sometimes it is not possible to create an alist or an obarray
1411 containing all the intended possible completions. In such a case, you
1412 can supply your own function to compute the completion of a given string.
1413 This is called @dfn{programmed completion}.
1415 To use this feature, pass a symbol with a function definition as the
1416 @var{collection} argument to @code{completing-read}. The function
1417 @code{completing-read} arranges to pass your completion function along
1418 to @code{try-completion} and @code{all-completions}, which will then let
1419 your function do all the work.
1421 The completion function should accept three arguments:
1425 The string to be completed.
1428 The predicate function to filter possible matches, or @code{nil} if
1429 none. Your function should call the predicate for each possible match,
1430 and ignore the possible match if the predicate returns @code{nil}.
1433 A flag specifying the type of operation.
1436 There are three flag values for three operations:
1440 @code{nil} specifies @code{try-completion}. The completion function
1441 should return the completion of the specified string, or @code{t} if the
1442 string is a unique and exact match already, or @code{nil} if the string
1443 matches no possibility.
1445 If the string is an exact match for one possibility, but also matches
1446 other longer possibilities, the function should return the string, not
1450 @code{t} specifies @code{all-completions}. The completion function
1451 should return a list of all possible completions of the specified
1455 @code{lambda} specifies @code{test-completion}. The completion
1456 function should return @code{t} if the specified string is an exact
1457 match for some possibility; @code{nil} otherwise.
1460 It would be consistent and clean for completion functions to allow
1461 lambda expressions (lists that are functions) as well as function
1462 symbols as @var{collection}, but this is impossible. Lists as
1463 completion tables already have other meanings, and it would be
1464 unreliable to treat one differently just because it is also a possible
1465 function. So you must arrange for any function you wish to use for
1466 completion to be encapsulated in a symbol.
1468 Emacs uses programmed completion when completing file names.
1469 @xref{File Name Completion}.
1471 @defmac dynamic-completion-table function
1472 This macro is a convenient way to write a function that can act as
1473 programmed completion function. The argument @var{function} should be
1474 a function that takes one argument, a string, and returns an alist of
1475 possible completions of it. You can think of
1476 @code{dynamic-completion-table} as a transducer between that interface
1477 and the interface for programmed completion functions.
1480 @node Yes-or-No Queries
1481 @section Yes-or-No Queries
1482 @cindex asking the user questions
1483 @cindex querying the user
1484 @cindex yes-or-no questions
1486 This section describes functions used to ask the user a yes-or-no
1487 question. The function @code{y-or-n-p} can be answered with a single
1488 character; it is useful for questions where an inadvertent wrong answer
1489 will not have serious consequences. @code{yes-or-no-p} is suitable for
1490 more momentous questions, since it requires three or four characters to
1493 If either of these functions is called in a command that was invoked
1494 using the mouse---more precisely, if @code{last-nonmenu-event}
1495 (@pxref{Command Loop Info}) is either @code{nil} or a list---then it
1496 uses a dialog box or pop-up menu to ask the question. Otherwise, it
1497 uses keyboard input. You can force use of the mouse or use of keyboard
1498 input by binding @code{last-nonmenu-event} to a suitable value around
1501 Strictly speaking, @code{yes-or-no-p} uses the minibuffer and
1502 @code{y-or-n-p} does not; but it seems best to describe them together.
1504 @defun y-or-n-p prompt
1505 This function asks the user a question, expecting input in the echo
1506 area. It returns @code{t} if the user types @kbd{y}, @code{nil} if the
1507 user types @kbd{n}. This function also accepts @key{SPC} to mean yes
1508 and @key{DEL} to mean no. It accepts @kbd{C-]} to mean ``quit'', like
1509 @kbd{C-g}, because the question might look like a minibuffer and for
1510 that reason the user might try to use @kbd{C-]} to get out. The answer
1511 is a single character, with no @key{RET} needed to terminate it. Upper
1512 and lower case are equivalent.
1514 ``Asking the question'' means printing @var{prompt} in the echo area,
1515 followed by the string @w{@samp{(y or n) }}. If the input is not one of
1516 the expected answers (@kbd{y}, @kbd{n}, @kbd{@key{SPC}},
1517 @kbd{@key{DEL}}, or something that quits), the function responds
1518 @samp{Please answer y or n.}, and repeats the request.
1520 This function does not actually use the minibuffer, since it does not
1521 allow editing of the answer. It actually uses the echo area (@pxref{The
1522 Echo Area}), which uses the same screen space as the minibuffer. The
1523 cursor moves to the echo area while the question is being asked.
1525 The answers and their meanings, even @samp{y} and @samp{n}, are not
1526 hardwired. The keymap @code{query-replace-map} specifies them.
1527 @xref{Search and Replace}.
1529 In the following example, the user first types @kbd{q}, which is
1530 invalid. At the next prompt the user types @kbd{y}.
1534 (y-or-n-p "Do you need a lift? ")
1536 ;; @r{After evaluation of the preceding expression,}
1537 ;; @r{the following prompt appears in the echo area:}
1541 ---------- Echo area ----------
1542 Do you need a lift? (y or n)
1543 ---------- Echo area ----------
1546 ;; @r{If the user then types @kbd{q}, the following appears:}
1549 ---------- Echo area ----------
1550 Please answer y or n. Do you need a lift? (y or n)
1551 ---------- Echo area ----------
1554 ;; @r{When the user types a valid answer,}
1555 ;; @r{it is displayed after the question:}
1558 ---------- Echo area ----------
1559 Do you need a lift? (y or n) y
1560 ---------- Echo area ----------
1565 We show successive lines of echo area messages, but only one actually
1566 appears on the screen at a time.
1569 @defun y-or-n-p-with-timeout prompt seconds default-value
1570 Like @code{y-or-n-p}, except that if the user fails to answer within
1571 @var{seconds} seconds, this function stops waiting and returns
1572 @var{default-value}. It works by setting up a timer; see @ref{Timers}.
1573 The argument @var{seconds} may be an integer or a floating point number.
1576 @defun yes-or-no-p prompt
1577 This function asks the user a question, expecting input in the
1578 minibuffer. It returns @code{t} if the user enters @samp{yes},
1579 @code{nil} if the user types @samp{no}. The user must type @key{RET} to
1580 finalize the response. Upper and lower case are equivalent.
1582 @code{yes-or-no-p} starts by displaying @var{prompt} in the echo area,
1583 followed by @w{@samp{(yes or no) }}. The user must type one of the
1584 expected responses; otherwise, the function responds @samp{Please answer
1585 yes or no.}, waits about two seconds and repeats the request.
1587 @code{yes-or-no-p} requires more work from the user than
1588 @code{y-or-n-p} and is appropriate for more crucial decisions.
1594 (yes-or-no-p "Do you really want to remove everything? ")
1596 ;; @r{After evaluation of the preceding expression,}
1597 ;; @r{the following prompt appears,}
1598 ;; @r{with an empty minibuffer:}
1602 ---------- Buffer: minibuffer ----------
1603 Do you really want to remove everything? (yes or no)
1604 ---------- Buffer: minibuffer ----------
1609 If the user first types @kbd{y @key{RET}}, which is invalid because this
1610 function demands the entire word @samp{yes}, it responds by displaying
1611 these prompts, with a brief pause between them:
1615 ---------- Buffer: minibuffer ----------
1616 Please answer yes or no.
1617 Do you really want to remove everything? (yes or no)
1618 ---------- Buffer: minibuffer ----------
1623 @node Multiple Queries
1624 @section Asking Multiple Y-or-N Questions
1626 When you have a series of similar questions to ask, such as ``Do you
1627 want to save this buffer'' for each buffer in turn, you should use
1628 @code{map-y-or-n-p} to ask the collection of questions, rather than
1629 asking each question individually. This gives the user certain
1630 convenient facilities such as the ability to answer the whole series at
1633 @defun map-y-or-n-p prompter actor list &optional help action-alist no-cursor-in-echo-area
1634 This function asks the user a series of questions, reading a
1635 single-character answer in the echo area for each one.
1637 The value of @var{list} specifies the objects to ask questions about.
1638 It should be either a list of objects or a generator function. If it is
1639 a function, it should expect no arguments, and should return either the
1640 next object to ask about, or @code{nil} meaning stop asking questions.
1642 The argument @var{prompter} specifies how to ask each question. If
1643 @var{prompter} is a string, the question text is computed like this:
1646 (format @var{prompter} @var{object})
1650 where @var{object} is the next object to ask about (as obtained from
1653 If not a string, @var{prompter} should be a function of one argument
1654 (the next object to ask about) and should return the question text. If
1655 the value is a string, that is the question to ask the user. The
1656 function can also return @code{t} meaning do act on this object (and
1657 don't ask the user), or @code{nil} meaning ignore this object (and don't
1660 The argument @var{actor} says how to act on the answers that the user
1661 gives. It should be a function of one argument, and it is called with
1662 each object that the user says yes for. Its argument is always an
1663 object obtained from @var{list}.
1665 If the argument @var{help} is given, it should be a list of this form:
1668 (@var{singular} @var{plural} @var{action})
1672 where @var{singular} is a string containing a singular noun that
1673 describes the objects conceptually being acted on, @var{plural} is the
1674 corresponding plural noun, and @var{action} is a transitive verb
1675 describing what @var{actor} does.
1677 If you don't specify @var{help}, the default is @code{("object"
1678 "objects" "act on")}.
1680 Each time a question is asked, the user may enter @kbd{y}, @kbd{Y}, or
1681 @key{SPC} to act on that object; @kbd{n}, @kbd{N}, or @key{DEL} to skip
1682 that object; @kbd{!} to act on all following objects; @key{ESC} or
1683 @kbd{q} to exit (skip all following objects); @kbd{.} (period) to act on
1684 the current object and then exit; or @kbd{C-h} to get help. These are
1685 the same answers that @code{query-replace} accepts. The keymap
1686 @code{query-replace-map} defines their meaning for @code{map-y-or-n-p}
1687 as well as for @code{query-replace}; see @ref{Search and Replace}.
1689 You can use @var{action-alist} to specify additional possible answers
1690 and what they mean. It is an alist of elements of the form
1691 @code{(@var{char} @var{function} @var{help})}, each of which defines one
1692 additional answer. In this element, @var{char} is a character (the
1693 answer); @var{function} is a function of one argument (an object from
1694 @var{list}); @var{help} is a string.
1696 When the user responds with @var{char}, @code{map-y-or-n-p} calls
1697 @var{function}. If it returns non-@code{nil}, the object is considered
1698 ``acted upon'', and @code{map-y-or-n-p} advances to the next object in
1699 @var{list}. If it returns @code{nil}, the prompt is repeated for the
1702 Normally, @code{map-y-or-n-p} binds @code{cursor-in-echo-area} while
1703 prompting. But if @var{no-cursor-in-echo-area} is non-@code{nil}, it
1706 If @code{map-y-or-n-p} is called in a command that was invoked using the
1707 mouse---more precisely, if @code{last-nonmenu-event} (@pxref{Command
1708 Loop Info}) is either @code{nil} or a list---then it uses a dialog box
1709 or pop-up menu to ask the question. In this case, it does not use
1710 keyboard input or the echo area. You can force use of the mouse or use
1711 of keyboard input by binding @code{last-nonmenu-event} to a suitable
1712 value around the call.
1714 The return value of @code{map-y-or-n-p} is the number of objects acted on.
1717 @node Reading a Password
1718 @section Reading a Password
1719 @cindex passwords, reading
1721 To read a password to pass to another program, you can use the
1722 function @code{read-passwd}.
1724 @defun read-passwd prompt &optional confirm default
1725 This function reads a password, prompting with @var{prompt}. It does
1726 not echo the password as the user types it; instead, it echoes @samp{.}
1727 for each character in the password.
1729 The optional argument @var{confirm}, if non-@code{nil}, says to read the
1730 password twice and insist it must be the same both times. If it isn't
1731 the same, the user has to type it over and over until the last two
1734 The optional argument @var{default} specifies the default password to
1735 return if the user enters empty input. If @var{default} is @code{nil},
1736 then @code{read-passwd} returns the null string in that case.
1739 @node Minibuffer Commands
1740 @section Minibuffer Commands
1742 This section describes some commands meant for use in the
1745 @deffn Command exit-minibuffer
1746 This command exits the active minibuffer. It is normally bound to
1747 keys in minibuffer local keymaps.
1750 @deffn Command self-insert-and-exit
1751 This command exits the active minibuffer after inserting the last
1752 character typed on the keyboard (found in @code{last-command-char};
1753 @pxref{Command Loop Info}).
1756 @deffn Command previous-history-element n
1757 This command replaces the minibuffer contents with the value of the
1758 @var{n}th previous (older) history element.
1761 @deffn Command next-history-element n
1762 This command replaces the minibuffer contents with the value of the
1763 @var{n}th more recent history element.
1766 @deffn Command previous-matching-history-element pattern n
1767 This command replaces the minibuffer contents with the value of the
1768 @var{n}th previous (older) history element that matches @var{pattern} (a
1769 regular expression).
1772 @deffn Command next-matching-history-element pattern n
1773 This command replaces the minibuffer contents with the value of the
1774 @var{n}th next (newer) history element that matches @var{pattern} (a
1775 regular expression).
1778 @node Minibuffer Windows
1779 @section Minibuffer Windows
1781 These functions access and select minibuffer windows
1782 and test whether they are active.
1784 @defun active-minibuffer-window
1785 This function returns the currently active minibuffer window, or
1786 @code{nil} if none is currently active.
1789 @defun minibuffer-window &optional frame
1790 @anchor{Definition of minibuffer-window}
1791 This function returns the minibuffer window used for frame @var{frame}.
1792 If @var{frame} is @code{nil}, that stands for the current frame. Note
1793 that the minibuffer window used by a frame need not be part of that
1794 frame---a frame that has no minibuffer of its own necessarily uses some
1795 other frame's minibuffer window.
1798 @defun set-minibuffer-window window
1799 This function specifies @var{window} as the minibuffer window to use.
1800 This affects where the minibuffer is displayed if you put text in it
1801 without invoking the usual minibuffer commands. It has no effect on
1802 the usual minibuffer input functions because they all start by
1803 choosing the minibuffer window according to the current frame.
1807 @defun window-minibuffer-p &optional window
1808 This function returns non-@code{nil} if @var{window} is a minibuffer
1810 @var{window} defaults to the selected window.
1813 It is not correct to determine whether a given window is a minibuffer by
1814 comparing it with the result of @code{(minibuffer-window)}, because
1815 there can be more than one minibuffer window if there is more than one
1818 @defun minibuffer-window-active-p window
1819 This function returns non-@code{nil} if @var{window}, assumed to be
1820 a minibuffer window, is currently active.
1823 @node Minibuffer Contents
1824 @section Minibuffer Contents
1826 These functions access the minibuffer prompt and contents.
1828 @defun minibuffer-prompt
1829 This function returns the prompt string of the currently active
1830 minibuffer. If no minibuffer is active, it returns @code{nil}.
1833 @defun minibuffer-prompt-end
1834 @tindex minibuffer-prompt-end
1835 This function returns the current
1836 position of the end of the minibuffer prompt, if a minibuffer is
1837 current. Otherwise, it returns the minimum valid buffer position.
1840 @defun minibuffer-prompt-width
1841 This function returns the current display-width of the minibuffer
1842 prompt, if a minibuffer is current. Otherwise, it returns zero.
1845 @defun minibuffer-contents
1846 @tindex minibuffer-contents
1847 This function returns the editable
1848 contents of the minibuffer (that is, everything except the prompt) as
1849 a string, if a minibuffer is current. Otherwise, it returns the
1850 entire contents of the current buffer.
1853 @defun minibuffer-contents-no-properties
1854 @tindex minibuffer-contents-no-properties
1855 This is like @code{minibuffer-contents}, except that it does not copy text
1856 properties, just the characters themselves. @xref{Text Properties}.
1859 @defun minibuffer-completion-contents
1860 @tindex minibuffer-completion-contents
1861 This is like @code{minibuffer-contents}, except that it returns only
1862 the contents before point. That is the part that completion commands
1863 operate on. @xref{Minibuffer Completion}.
1866 @defun delete-minibuffer-contents
1867 @tindex delete-minibuffer-contents
1868 This function erases the editable contents of the minibuffer (that is,
1869 everything except the prompt), if a minibuffer is current. Otherwise,
1870 it erases the entire current buffer.
1873 @node Recursive Mini
1874 @section Recursive Minibuffers
1876 These functions and variables deal with recursive minibuffers
1877 (@pxref{Recursive Editing}):
1879 @defun minibuffer-depth
1880 This function returns the current depth of activations of the
1881 minibuffer, a nonnegative integer. If no minibuffers are active, it
1885 @defopt enable-recursive-minibuffers
1886 If this variable is non-@code{nil}, you can invoke commands (such as
1887 @code{find-file}) that use minibuffers even while the minibuffer window
1888 is active. Such invocation produces a recursive editing level for a new
1889 minibuffer. The outer-level minibuffer is invisible while you are
1890 editing the inner one.
1892 If this variable is @code{nil}, you cannot invoke minibuffer
1893 commands when the minibuffer window is active, not even if you switch to
1894 another window to do it.
1898 If a command name has a property @code{enable-recursive-minibuffers}
1899 that is non-@code{nil}, then the command can use the minibuffer to read
1900 arguments even if it is invoked from the minibuffer. A command can
1901 also achieve this by binding @code{enable-recursive-minibuffers}
1902 to @code{t} in the interactive declaration (@pxref{Using Interactive}).
1903 The minibuffer command @code{next-matching-history-element} (normally
1904 @kbd{M-s} in the minibuffer) does the latter.
1906 @node Minibuffer Misc
1907 @section Minibuffer Miscellany
1909 @defun minibufferp &optional buffer-or-name
1910 This function returns non-@code{nil} if @var{buffer-or-name} is a
1911 minibuffer. If @var{buffer-or-name} is omitted, it tests the current
1915 @defvar minibuffer-setup-hook
1916 This is a normal hook that is run whenever the minibuffer is entered.
1920 @defvar minibuffer-exit-hook
1921 This is a normal hook that is run whenever the minibuffer is exited.
1925 @defvar minibuffer-help-form
1926 @anchor{Definition of minibuffer-help-form}
1927 The current value of this variable is used to rebind @code{help-form}
1928 locally inside the minibuffer (@pxref{Help Functions}).
1931 @defvar minibuffer-scroll-window
1932 @anchor{Definition of minibuffer-scroll-window}
1933 If the value of this variable is non-@code{nil}, it should be a window
1934 object. When the function @code{scroll-other-window} is called in the
1935 minibuffer, it scrolls this window.
1938 @defun minibuffer-selected-window
1939 This function returns the window which was selected when the
1940 minibuffer was entered. If selected window is not a minibuffer
1941 window, it returns @code{nil}.
1944 @defopt max-mini-window-height
1945 This variable specifies the maximum height for resizing minibuffer
1946 windows. If a float, it specifies a fraction of the height of the
1947 frame. If an integer, it specifies a number of lines.
1950 @defun minibuffer-message string
1951 This function displays @var{string} temporarily at the end of the
1952 minibuffer text, for two seconds, or until the next input event
1953 arrives, whichever comes first.
1957 arch-tag: bba7f945-9078-477f-a2ce-18818a6e1218