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, 2007 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
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 Use of @var{initial-contents} is mostly deprecated; we recommend using
166 a non-@code{nil} value only in conjunction with specifying a cons cell
167 for @var{hist}. @xref{Initial Input}.
170 @defun read-string prompt &optional initial history default inherit-input-method
171 This function reads a string from the minibuffer and returns it. The
172 arguments @var{prompt}, @var{initial}, @var{history} and
173 @var{inherit-input-method} are used as in @code{read-from-minibuffer}.
174 The keymap used is @code{minibuffer-local-map}.
176 The optional argument @var{default} is used as in
177 @code{read-from-minibuffer}, except that, if non-@code{nil}, it also
178 specifies a default value to return if the user enters null input. As
179 in @code{read-from-minibuffer} it should be a string, or @code{nil},
180 which is equivalent to an empty string.
182 This function is a simplified interface to the
183 @code{read-from-minibuffer} function:
187 (read-string @var{prompt} @var{initial} @var{history} @var{default} @var{inherit})
190 (read-from-minibuffer @var{prompt} @var{initial} nil nil
191 @var{history} @var{default} @var{inherit})))
192 (if (and (equal value "") @var{default})
199 @defvar minibuffer-allow-text-properties
200 If this variable is @code{nil}, then @code{read-from-minibuffer} strips
201 all text properties from the minibuffer input before returning it.
202 This variable also affects @code{read-string}. However,
203 @code{read-no-blanks-input} (see below), as well as
204 @code{read-minibuffer} and related functions (@pxref{Object from
205 Minibuffer,, Reading Lisp Objects With the Minibuffer}), and all
206 functions that do minibuffer input with completion, discard text
207 properties unconditionally, regardless of the value of this variable.
210 @defvar minibuffer-local-map
212 @anchor{Definition of minibuffer-local-map}
213 @c avoid page break at anchor; work around Texinfo deficiency
214 is the default local keymap for reading from the minibuffer. By
215 default, it makes the following bindings:
219 @code{exit-minibuffer}
222 @code{exit-minibuffer}
225 @code{abort-recursive-edit}
229 @code{next-history-element}
233 @code{previous-history-element}
236 @code{next-matching-history-element}
239 @code{previous-matching-history-element}
243 @c In version 18, initial is required
245 @defun read-no-blanks-input prompt &optional initial inherit-input-method
246 This function reads a string from the minibuffer, but does not allow
247 whitespace characters as part of the input: instead, those characters
248 terminate the input. The arguments @var{prompt}, @var{initial}, and
249 @var{inherit-input-method} are used as in @code{read-from-minibuffer}.
251 This is a simplified interface to the @code{read-from-minibuffer}
252 function, and passes the value of the @code{minibuffer-local-ns-map}
253 keymap as the @var{keymap} argument for that function. Since the keymap
254 @code{minibuffer-local-ns-map} does not rebind @kbd{C-q}, it @emph{is}
255 possible to put a space into the string, by quoting it.
257 This function discards text properties, regardless of the value of
258 @code{minibuffer-allow-text-properties}.
262 (read-no-blanks-input @var{prompt} @var{initial})
264 (let (minibuffer-allow-text-properties)
265 (read-from-minibuffer @var{prompt} @var{initial} minibuffer-local-ns-map))
270 @defvar minibuffer-local-ns-map
271 This built-in variable is the keymap used as the minibuffer local keymap
272 in the function @code{read-no-blanks-input}. By default, it makes the
273 following bindings, in addition to those of @code{minibuffer-local-map}:
277 @cindex @key{SPC} in minibuffer
278 @code{exit-minibuffer}
281 @cindex @key{TAB} in minibuffer
282 @code{exit-minibuffer}
285 @cindex @kbd{?} in minibuffer
286 @code{self-insert-and-exit}
290 @node Object from Minibuffer
291 @section Reading Lisp Objects with the Minibuffer
293 This section describes functions for reading Lisp objects with the
296 @defun read-minibuffer prompt &optional initial
297 This function reads a Lisp object using the minibuffer, and returns it
298 without evaluating it. The arguments @var{prompt} and @var{initial} are
299 used as in @code{read-from-minibuffer}.
301 This is a simplified interface to the
302 @code{read-from-minibuffer} function:
306 (read-minibuffer @var{prompt} @var{initial})
308 (let (minibuffer-allow-text-properties)
309 (read-from-minibuffer @var{prompt} @var{initial} nil t))
313 Here is an example in which we supply the string @code{"(testing)"} as
319 "Enter an expression: " (format "%s" '(testing)))
321 ;; @r{Here is how the minibuffer is displayed:}
325 ---------- Buffer: Minibuffer ----------
326 Enter an expression: (testing)@point{}
327 ---------- Buffer: Minibuffer ----------
332 The user can type @key{RET} immediately to use the initial input as a
333 default, or can edit the input.
336 @defun eval-minibuffer prompt &optional initial
337 This function reads a Lisp expression using the minibuffer, evaluates
338 it, then returns the result. The arguments @var{prompt} and
339 @var{initial} are used as in @code{read-from-minibuffer}.
341 This function simply evaluates the result of a call to
342 @code{read-minibuffer}:
346 (eval-minibuffer @var{prompt} @var{initial})
348 (eval (read-minibuffer @var{prompt} @var{initial}))
353 @defun edit-and-eval-command prompt form
354 This function reads a Lisp expression in the minibuffer, and then
355 evaluates it. The difference between this command and
356 @code{eval-minibuffer} is that here the initial @var{form} is not
357 optional and it is treated as a Lisp object to be converted to printed
358 representation rather than as a string of text. It is printed with
359 @code{prin1}, so if it is a string, double-quote characters (@samp{"})
360 appear in the initial text. @xref{Output Functions}.
362 The first thing @code{edit-and-eval-command} does is to activate the
363 minibuffer with @var{prompt} as the prompt. Then it inserts the printed
364 representation of @var{form} in the minibuffer, and lets the user edit it.
365 When the user exits the minibuffer, the edited text is read with
366 @code{read} and then evaluated. The resulting value becomes the value
367 of @code{edit-and-eval-command}.
369 In the following example, we offer the user an expression with initial
370 text which is a valid form already:
374 (edit-and-eval-command "Please edit: " '(forward-word 1))
376 ;; @r{After evaluation of the preceding expression,}
377 ;; @r{the following appears in the minibuffer:}
381 ---------- Buffer: Minibuffer ----------
382 Please edit: (forward-word 1)@point{}
383 ---------- Buffer: Minibuffer ----------
388 Typing @key{RET} right away would exit the minibuffer and evaluate the
389 expression, thus moving point forward one word.
390 @code{edit-and-eval-command} returns @code{nil} in this example.
393 @node Minibuffer History
394 @section Minibuffer History
395 @cindex minibuffer history
398 A @dfn{minibuffer history list} records previous minibuffer inputs so
399 the user can reuse them conveniently. A history list is actually a
400 symbol, not a list; it is a variable whose value is a list of strings
401 (previous inputs), most recent first.
403 There are many separate history lists, used for different kinds of
404 inputs. It's the Lisp programmer's job to specify the right history
405 list for each use of the minibuffer.
407 You specify the history list with the optional @var{hist} argument
408 to either @code{read-from-minibuffer} or @code{completing-read}. Here
409 are the possible values for it:
413 Use @var{variable} (a symbol) as the history list.
415 @item (@var{variable} . @var{startpos})
416 Use @var{variable} (a symbol) as the history list, and assume that the
417 initial history position is @var{startpos} (a nonnegative integer).
419 Specifying 0 for @var{startpos} is equivalent to just specifying the
420 symbol @var{variable}. @code{previous-history-element} will display
421 the most recent element of the history list in the minibuffer. If you
422 specify a positive @var{startpos}, the minibuffer history functions
423 behave as if @code{(elt @var{variable} (1- @var{STARTPOS}))} were the
424 history element currently shown in the minibuffer.
426 For consistency, you should also specify that element of the history
427 as the initial minibuffer contents, using the @var{initial} argument
428 to the minibuffer input function (@pxref{Initial Input}).
431 If you don't specify @var{hist}, then the default history list
432 @code{minibuffer-history} is used. For other standard history lists,
433 see below. You can also create your own history list variable; just
434 initialize it to @code{nil} before the first use.
436 Both @code{read-from-minibuffer} and @code{completing-read} add new
437 elements to the history list automatically, and provide commands to
438 allow the user to reuse items on the list. The only thing your program
439 needs to do to use a history list is to initialize it and to pass its
440 name to the input functions when you wish. But it is safe to modify the
441 list by hand when the minibuffer input functions are not using it.
443 Emacs functions that add a new element to a history list can also
444 delete old elements if the list gets too long. The variable
445 @code{history-length} specifies the maximum length for most history
446 lists. To specify a different maximum length for a particular history
447 list, put the length in the @code{history-length} property of the
448 history list symbol. The variable @code{history-delete-duplicates}
449 specifies whether to delete duplicates in history.
451 @defun add-to-history history-var newelt &optional maxelt keep-all
452 This function adds a new element @var{newelt}, if it isn't the empty
453 string, to the history list stored in the variable @var{history-var},
454 and returns the updated history list. It limits the list length to
455 the value of @var{maxelt} (if non-@code{nil}) or @code{history-length}
456 (described below). The possible values of @var{maxelt} have the same
457 meaning as the values of @code{history-length}.
459 Normally, @code{add-to-history} removes duplicate members from the
460 history list if @code{history-delete-duplicates} is non-@code{nil}.
461 However, if @var{keep-all} is non-@code{nil}, that says not to remove
462 duplicates, and to add @var{newelt} to the list even if it is empty.
465 @defvar history-add-new-input
466 If the value of this variable is @code{nil}, standard functions that
467 read from the minibuffer don't add new elements to the history list.
468 This lets Lisp programs explicitly manage input history by using
469 @code{add-to-history}. By default, @code{history-add-new-input} is
470 set to a non-@code{nil} value.
473 @defvar history-length
474 The value of this variable specifies the maximum length for all
475 history lists that don't specify their own maximum lengths. If the
476 value is @code{t}, that means there no maximum (don't delete old
477 elements). The value of @code{history-length} property of the history
478 list variable's symbol, if set, overrides this variable for that
479 particular history list.
482 @defvar history-delete-duplicates
483 If the value of this variable is @code{t}, that means when adding a
484 new history element, all previous identical elements are deleted.
487 Here are some of the standard minibuffer history list variables:
489 @defvar minibuffer-history
490 The default history list for minibuffer history input.
493 @defvar query-replace-history
494 A history list for arguments to @code{query-replace} (and similar
495 arguments to other commands).
498 @defvar file-name-history
499 A history list for file-name arguments.
502 @defvar buffer-name-history
503 A history list for buffer-name arguments.
506 @defvar regexp-history
507 A history list for regular expression arguments.
510 @defvar extended-command-history
511 A history list for arguments that are names of extended commands.
514 @defvar shell-command-history
515 A history list for arguments that are shell commands.
518 @defvar read-expression-history
519 A history list for arguments that are Lisp expressions to evaluate.
523 @section Initial Input
525 Several of the functions for minibuffer input have an argument called
526 @var{initial} or @var{initial-contents}. This is a mostly-deprecated
527 feature for specifying that the minibuffer should start out with
528 certain text, instead of empty as usual.
530 If @var{initial} is a string, the minibuffer starts out containing the
531 text of the string, with point at the end, when the user starts to
532 edit the text. If the user simply types @key{RET} to exit the
533 minibuffer, it will use the initial input string to determine the
536 @strong{We discourage use of a non-@code{nil} value for
537 @var{initial}}, because initial input is an intrusive interface.
538 History lists and default values provide a much more convenient method
539 to offer useful default inputs to the user.
541 There is just one situation where you should specify a string for an
542 @var{initial} argument. This is when you specify a cons cell for the
543 @var{hist} or @var{history} argument. @xref{Minibuffer History}.
545 @var{initial} can also be a cons cell of the form @code{(@var{string}
546 . @var{position})}. This means to insert @var{string} in the
547 minibuffer but put point at @var{position} within the string's text.
549 As a historical accident, @var{position} was implemented
550 inconsistently in different functions. In @code{completing-read},
551 @var{position}'s value is interpreted as origin-zero; that is, a value
552 of 0 means the beginning of the string, 1 means after the first
553 character, etc. In @code{read-minibuffer}, and the other
554 non-completion minibuffer input functions that support this argument,
555 1 means the beginning of the string 2 means after the first character,
558 Use of a cons cell as the value for @var{initial} arguments is
559 deprecated in user code.
565 @dfn{Completion} is a feature that fills in the rest of a name
566 starting from an abbreviation for it. Completion works by comparing the
567 user's input against a list of valid names and determining how much of
568 the name is determined uniquely by what the user has typed. For
569 example, when you type @kbd{C-x b} (@code{switch-to-buffer}) and then
570 type the first few letters of the name of the buffer to which you wish
571 to switch, and then type @key{TAB} (@code{minibuffer-complete}), Emacs
572 extends the name as far as it can.
574 Standard Emacs commands offer completion for names of symbols, files,
575 buffers, and processes; with the functions in this section, you can
576 implement completion for other kinds of names.
578 The @code{try-completion} function is the basic primitive for
579 completion: it returns the longest determined completion of a given
580 initial string, with a given set of strings to match against.
582 The function @code{completing-read} provides a higher-level interface
583 for completion. A call to @code{completing-read} specifies how to
584 determine the list of valid names. The function then activates the
585 minibuffer with a local keymap that binds a few keys to commands useful
586 for completion. Other functions provide convenient simple interfaces
587 for reading certain kinds of names with completion.
590 * Basic Completion:: Low-level functions for completing strings.
591 (These are too low level to use the minibuffer.)
592 * Minibuffer Completion:: Invoking the minibuffer with completion.
593 * Completion Commands:: Minibuffer commands that do completion.
594 * High-Level Completion:: Convenient special cases of completion
595 (reading buffer name, file name, etc.)
596 * Reading File Names:: Using completion to read file names.
597 * Programmed Completion:: Writing your own completion-function.
600 @node Basic Completion
601 @subsection Basic Completion Functions
603 The completion functions @code{try-completion},
604 @code{all-completions} and @code{test-completion} have nothing in
605 themselves to do with minibuffers. We describe them in this chapter
606 so as to keep them near the higher-level completion features that do
609 If you store a completion alist in a variable, you should mark the
610 variable as ``risky'' with a non-@code{nil}
611 @code{risky-local-variable} property.
613 @defun try-completion string collection &optional predicate
614 This function returns the longest common substring of all possible
615 completions of @var{string} in @var{collection}. The value of
616 @var{collection} must be a list of strings or symbols, an alist, an
617 obarray, a hash table, or a function that implements a virtual set of
620 Completion compares @var{string} against each of the permissible
621 completions specified by @var{collection}; if the beginning of the
622 permissible completion equals @var{string}, it matches. If no permissible
623 completions match, @code{try-completion} returns @code{nil}. If only
624 one permissible completion matches, and the match is exact, then
625 @code{try-completion} returns @code{t}. Otherwise, the value is the
626 longest initial sequence common to all the permissible completions that
629 If @var{collection} is an alist (@pxref{Association Lists}), the
630 permissible completions are the elements of the alist that are either
631 strings, symbols, or conses whose @sc{car} is a string or symbol.
632 Symbols are converted to strings using @code{symbol-name}. Other
633 elements of the alist are ignored. (Remember that in Emacs Lisp, the
634 elements of alists do not @emph{have} to be conses.) In particular, a
635 list of strings or symbols is allowed, even though we usually do not
636 think of such lists as alists.
638 @cindex obarray in completion
639 If @var{collection} is an obarray (@pxref{Creating Symbols}), the names
640 of all symbols in the obarray form the set of permissible completions. The
641 global variable @code{obarray} holds an obarray containing the names of
642 all interned Lisp symbols.
644 Note that the only valid way to make a new obarray is to create it
645 empty and then add symbols to it one by one using @code{intern}.
646 Also, you cannot intern a given symbol in more than one obarray.
648 If @var{collection} is a hash table, then the keys that are strings
649 are the possible completions. Other keys are ignored.
651 You can also use a symbol that is a function as @var{collection}. Then
652 the function is solely responsible for performing completion;
653 @code{try-completion} returns whatever this function returns. The
654 function is called with three arguments: @var{string}, @var{predicate}
655 and @code{nil}. (The reason for the third argument is so that the same
656 function can be used in @code{all-completions} and do the appropriate
657 thing in either case.) @xref{Programmed Completion}.
659 If the argument @var{predicate} is non-@code{nil}, then it must be a
660 function of one argument, unless @var{collection} is a hash table, in
661 which case it should be a function of two arguments. It is used to
662 test each possible match, and the match is accepted only if
663 @var{predicate} returns non-@code{nil}. The argument given to
664 @var{predicate} is either a string or a cons cell (the @sc{car} of
665 which is a string) from the alist, or a symbol (@emph{not} a symbol
666 name) from the obarray. If @var{collection} is a hash table,
667 @var{predicate} is called with two arguments, the string key and the
670 In addition, to be acceptable, a completion must also match all the
671 regular expressions in @code{completion-regexp-list}. (Unless
672 @var{collection} is a function, in which case that function has to
673 handle @code{completion-regexp-list} itself.)
675 In the first of the following examples, the string @samp{foo} is
676 matched by three of the alist @sc{car}s. All of the matches begin with
677 the characters @samp{fooba}, so that is the result. In the second
678 example, there is only one possible match, and it is exact, so the value
685 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)))
690 (try-completion "foo" '(("barfoo" 2) ("foo" 3)))
695 In the following example, numerous symbols begin with the characters
696 @samp{forw}, and all of them begin with the word @samp{forward}. In
697 most of the symbols, this is followed with a @samp{-}, but not in all,
698 so no more than @samp{forward} can be completed.
702 (try-completion "forw" obarray)
707 Finally, in the following example, only two of the three possible
708 matches pass the predicate @code{test} (the string @samp{foobaz} is
709 too short). Both of those begin with the string @samp{foobar}.
714 (> (length (car s)) 6))
720 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
727 @defun all-completions string collection &optional predicate nospace
728 This function returns a list of all possible completions of
729 @var{string}. The arguments to this function (aside from
730 @var{nospace}) are the same as those of @code{try-completion}. Also,
731 this function uses @code{completion-regexp-list} in the same way that
732 @code{try-completion} does. The optional argument @var{nospace} only
733 matters if @var{string} is the empty string. In that case, if
734 @var{nospace} is non-@code{nil}, completions that start with a space
737 If @var{collection} is a function, it is called with three arguments:
738 @var{string}, @var{predicate} and @code{t}; then @code{all-completions}
739 returns whatever the function returns. @xref{Programmed Completion}.
741 Here is an example, using the function @code{test} shown in the
742 example for @code{try-completion}:
747 (> (length (car s)) 6))
754 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
756 @result{} ("foobar1" "foobar2")
761 @defun test-completion string collection &optional predicate
762 @anchor{Definition of test-completion}
763 This function returns non-@code{nil} if @var{string} is a valid
764 completion possibility specified by @var{collection} and
765 @var{predicate}. The arguments are the same as in
766 @code{try-completion}. For instance, if @var{collection} is a list of
767 strings, this is true if @var{string} appears in the list and
768 @var{predicate} is satisfied.
770 This function uses @code{completion-regexp-list} in the same
771 way that @code{try-completion} does.
773 If @var{predicate} is non-@code{nil} and if @var{collection} contains
774 several strings that are equal to each other, as determined by
775 @code{compare-strings} according to @code{completion-ignore-case},
776 then @var{predicate} should accept either all or none of them.
777 Otherwise, the return value of @code{test-completion} is essentially
780 If @var{collection} is a function, it is called with three arguments,
781 the values @var{string}, @var{predicate} and @code{lambda}; whatever
782 it returns, @code{test-completion} returns in turn.
785 @defvar completion-ignore-case
786 If the value of this variable is non-@code{nil}, Emacs does not
787 consider case significant in completion.
790 @defvar completion-regexp-list
791 This is a list of regular expressions. The completion functions only
792 consider a completion acceptable if it matches all regular expressions
793 in this list, with @code{case-fold-search} (@pxref{Searching and Case})
794 bound to the value of @code{completion-ignore-case}.
797 @defmac lazy-completion-table var fun
798 This macro provides a way to initialize the variable @var{var} as a
799 collection for completion in a lazy way, not computing its actual
800 contents until they are first needed. You use this macro to produce a
801 value that you store in @var{var}. The actual computation of the
802 proper value is done the first time you do completion using @var{var}.
803 It is done by calling @var{fun} with no arguments. The
804 value @var{fun} returns becomes the permanent value of @var{var}.
806 Here is an example of use:
809 (defvar foo (lazy-completion-table foo make-my-alist))
813 @node Minibuffer Completion
814 @subsection Completion and the Minibuffer
815 @cindex minibuffer completion
816 @cindex reading from minibuffer with completion
818 This section describes the basic interface for reading from the
819 minibuffer with completion.
821 @defun completing-read prompt collection &optional predicate require-match initial hist default inherit-input-method
822 This function reads a string in the minibuffer, assisting the user by
823 providing completion. It activates the minibuffer with prompt
824 @var{prompt}, which must be a string.
826 The actual completion is done by passing @var{collection} and
827 @var{predicate} to the function @code{try-completion}. This happens
828 in certain commands bound in the local keymaps used for completion.
829 Some of these commands also call @code{test-completion}. Thus, if
830 @var{predicate} is non-@code{nil}, it should be compatible with
831 @var{collection} and @code{completion-ignore-case}. @xref{Definition
834 If @var{require-match} is @code{nil}, the exit commands work regardless
835 of the input in the minibuffer. If @var{require-match} is @code{t}, the
836 usual minibuffer exit commands won't exit unless the input completes to
837 an element of @var{collection}. If @var{require-match} is neither
838 @code{nil} nor @code{t}, then the exit commands won't exit unless the
839 input already in the buffer matches an element of @var{collection}.
841 However, empty input is always permitted, regardless of the value of
842 @var{require-match}; in that case, @code{completing-read} returns
843 @var{default}, or @code{""}, if @var{default} is @code{nil}. The
844 value of @var{default} (if non-@code{nil}) is also available to the
845 user through the history commands.
847 The function @code{completing-read} uses
848 @code{minibuffer-local-completion-map} as the keymap if
849 @var{require-match} is @code{nil}, and uses
850 @code{minibuffer-local-must-match-map} if @var{require-match} is
851 non-@code{nil}. @xref{Completion Commands}.
853 The argument @var{hist} specifies which history list variable to use for
854 saving the input and for minibuffer history commands. It defaults to
855 @code{minibuffer-history}. @xref{Minibuffer History}.
857 The argument @var{initial} is mostly deprecated; we recommend using a
858 non-@code{nil} value only in conjunction with specifying a cons cell
859 for @var{hist}. @xref{Initial Input}. For default input, use
860 @var{default} instead.
862 If the argument @var{inherit-input-method} is non-@code{nil}, then the
863 minibuffer inherits the current input method (@pxref{Input
864 Methods}) and the setting of @code{enable-multibyte-characters}
865 (@pxref{Text Representations}) from whichever buffer was current before
866 entering the minibuffer.
868 If the built-in variable @code{completion-ignore-case} is
869 non-@code{nil}, completion ignores case when comparing the input
870 against the possible matches. @xref{Basic Completion}. In this mode
871 of operation, @var{predicate} must also ignore case, or you will get
874 Here's an example of using @code{completing-read}:
880 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
885 ;; @r{After evaluation of the preceding expression,}
886 ;; @r{the following appears in the minibuffer:}
888 ---------- Buffer: Minibuffer ----------
889 Complete a foo: fo@point{}
890 ---------- Buffer: Minibuffer ----------
895 If the user then types @kbd{@key{DEL} @key{DEL} b @key{RET}},
896 @code{completing-read} returns @code{barfoo}.
898 The @code{completing-read} function binds variables to pass
899 information to the commands that actually do completion.
900 They are described in the following section.
903 @node Completion Commands
904 @subsection Minibuffer Commands that Do Completion
906 This section describes the keymaps, commands and user options used
907 in the minibuffer to do completion. The description refers to the
908 situation when Partial Completion mode is disabled (as it is by
909 default). When enabled, this minor mode uses its own alternatives to
910 some of the commands described below. @xref{Completion Options,,,
911 emacs, The GNU Emacs Manual}, for a short description of Partial
914 @defvar minibuffer-completion-table
915 The value of this variable is the collection used for completion in
916 the minibuffer. This is the global variable that contains what
917 @code{completing-read} passes to @code{try-completion}. It is used by
918 minibuffer completion commands such as @code{minibuffer-complete-word}.
921 @defvar minibuffer-completion-predicate
922 This variable's value is the predicate that @code{completing-read}
923 passes to @code{try-completion}. The variable is also used by the other
924 minibuffer completion functions.
927 @defvar minibuffer-completion-confirm
928 When the value of this variable is non-@code{nil}, Emacs asks for
929 confirmation of a completion before exiting the minibuffer.
930 @code{completing-read} binds this variable, and the function
931 @code{minibuffer-complete-and-exit} checks the value before exiting.
934 @deffn Command minibuffer-complete-word
935 This function completes the minibuffer contents by at most a single
936 word. Even if the minibuffer contents have only one completion,
937 @code{minibuffer-complete-word} does not add any characters beyond the
938 first character that is not a word constituent. @xref{Syntax Tables}.
941 @deffn Command minibuffer-complete
942 This function completes the minibuffer contents as far as possible.
945 @deffn Command minibuffer-complete-and-exit
946 This function completes the minibuffer contents, and exits if
947 confirmation is not required, i.e., if
948 @code{minibuffer-completion-confirm} is @code{nil}. If confirmation
949 @emph{is} required, it is given by repeating this command
950 immediately---the command is programmed to work without confirmation
951 when run twice in succession.
954 @deffn Command minibuffer-completion-help
955 This function creates a list of the possible completions of the
956 current minibuffer contents. It works by calling @code{all-completions}
957 using the value of the variable @code{minibuffer-completion-table} as
958 the @var{collection} argument, and the value of
959 @code{minibuffer-completion-predicate} as the @var{predicate} argument.
960 The list of completions is displayed as text in a buffer named
961 @samp{*Completions*}.
964 @defun display-completion-list completions &optional common-substring
965 This function displays @var{completions} to the stream in
966 @code{standard-output}, usually a buffer. (@xref{Read and Print}, for more
967 information about streams.) The argument @var{completions} is normally
968 a list of completions just returned by @code{all-completions}, but it
969 does not have to be. Each element may be a symbol or a string, either
970 of which is simply printed. It can also be a list of two strings,
971 which is printed as if the strings were concatenated. The first of
972 the two strings is the actual completion, the second string serves as
975 The argument @var{common-substring} is the prefix that is common to
976 all the completions. With normal Emacs completion, it is usually the
977 same as the string that was completed. @code{display-completion-list}
978 uses this to highlight text in the completion list for better visual
979 feedback. This is not needed in the minibuffer; for minibuffer
980 completion, you can pass @code{nil}.
982 This function is called by @code{minibuffer-completion-help}. The
983 most common way to use it is together with
984 @code{with-output-to-temp-buffer}, like this:
987 (with-output-to-temp-buffer "*Completions*"
988 (display-completion-list
989 (all-completions (buffer-string) my-alist)
994 @defopt completion-auto-help
995 If this variable is non-@code{nil}, the completion commands
996 automatically display a list of possible completions whenever nothing
997 can be completed because the next character is not uniquely determined.
1000 @defvar minibuffer-local-completion-map
1001 @code{completing-read} uses this value as the local keymap when an
1002 exact match of one of the completions is not required. By default, this
1003 keymap makes the following bindings:
1007 @code{minibuffer-completion-help}
1010 @code{minibuffer-complete-word}
1013 @code{minibuffer-complete}
1017 with other characters bound as in @code{minibuffer-local-map}
1018 (@pxref{Definition of minibuffer-local-map}).
1021 @defvar minibuffer-local-must-match-map
1022 @code{completing-read} uses this value as the local keymap when an
1023 exact match of one of the completions is required. Therefore, no keys
1024 are bound to @code{exit-minibuffer}, the command that exits the
1025 minibuffer unconditionally. By default, this keymap makes the following
1030 @code{minibuffer-completion-help}
1033 @code{minibuffer-complete-word}
1036 @code{minibuffer-complete}
1039 @code{minibuffer-complete-and-exit}
1042 @code{minibuffer-complete-and-exit}
1046 with other characters bound as in @code{minibuffer-local-map}.
1049 @defvar minibuffer-local-filename-completion-map
1050 This is like @code{minibuffer-local-completion-map}
1051 except that it does not bind @key{SPC}. This keymap is used by the
1052 function @code{read-file-name}.
1055 @defvar minibuffer-local-must-match-filename-map
1056 This is like @code{minibuffer-local-must-match-map}
1057 except that it does not bind @key{SPC}. This keymap is used by the
1058 function @code{read-file-name}.
1061 @node High-Level Completion
1062 @subsection High-Level Completion Functions
1064 This section describes the higher-level convenient functions for
1065 reading certain sorts of names with completion.
1067 In most cases, you should not call these functions in the middle of a
1068 Lisp function. When possible, do all minibuffer input as part of
1069 reading the arguments for a command, in the @code{interactive}
1070 specification. @xref{Defining Commands}.
1072 @defun read-buffer prompt &optional default existing
1073 This function reads the name of a buffer and returns it as a string.
1074 The argument @var{default} is the default name to use, the value to
1075 return if the user exits with an empty minibuffer. If non-@code{nil},
1076 it should be a string or a buffer. It is mentioned in the prompt, but
1077 is not inserted in the minibuffer as initial input.
1079 The argument @var{prompt} should be a string ending with a colon and a
1080 space. If @var{default} is non-@code{nil}, the function inserts it in
1081 @var{prompt} before the colon to follow the convention for reading from
1082 the minibuffer with a default value (@pxref{Programming Tips}).
1084 If @var{existing} is non-@code{nil}, then the name specified must be
1085 that of an existing buffer. The usual commands to exit the minibuffer
1086 do not exit if the text is not valid, and @key{RET} does completion to
1087 attempt to find a valid name. If @var{existing} is neither @code{nil}
1088 nor @code{t}, confirmation is required after completion. (However,
1089 @var{default} is not checked for validity; it is returned, whatever it
1090 is, if the user exits with the minibuffer empty.)
1092 In the following example, the user enters @samp{minibuffer.t}, and
1093 then types @key{RET}. The argument @var{existing} is @code{t}, and the
1094 only buffer name starting with the given input is
1095 @samp{minibuffer.texi}, so that name is the value.
1098 (read-buffer "Buffer name: " "foo" t)
1100 ;; @r{After evaluation of the preceding expression,}
1101 ;; @r{the following prompt appears,}
1102 ;; @r{with an empty minibuffer:}
1106 ---------- Buffer: Minibuffer ----------
1107 Buffer name (default foo): @point{}
1108 ---------- Buffer: Minibuffer ----------
1112 ;; @r{The user types @kbd{minibuffer.t @key{RET}}.}
1113 @result{} "minibuffer.texi"
1118 @defvar read-buffer-function
1119 This variable specifies how to read buffer names. For example, if you
1120 set this variable to @code{iswitchb-read-buffer}, all Emacs commands
1121 that call @code{read-buffer} to read a buffer name will actually use the
1122 @code{iswitchb} package to read it.
1125 @defun read-command prompt &optional default
1126 This function reads the name of a command and returns it as a Lisp
1127 symbol. The argument @var{prompt} is used as in
1128 @code{read-from-minibuffer}. Recall that a command is anything for
1129 which @code{commandp} returns @code{t}, and a command name is a symbol
1130 for which @code{commandp} returns @code{t}. @xref{Interactive Call}.
1132 The argument @var{default} specifies what to return if the user enters
1133 null input. It can be a symbol or a string; if it is a string,
1134 @code{read-command} interns it before returning it. If @var{default} is
1135 @code{nil}, that means no default has been specified; then if the user
1136 enters null input, the return value is @code{(intern "")}, that is, a
1137 symbol whose name is an empty string.
1140 (read-command "Command name? ")
1143 ;; @r{After evaluation of the preceding expression,}
1144 ;; @r{the following prompt appears with an empty minibuffer:}
1148 ---------- Buffer: Minibuffer ----------
1150 ---------- Buffer: Minibuffer ----------
1155 If the user types @kbd{forward-c @key{RET}}, then this function returns
1156 @code{forward-char}.
1158 The @code{read-command} function is a simplified interface to
1159 @code{completing-read}. It uses the variable @code{obarray} so as to
1160 complete in the set of extant Lisp symbols, and it uses the
1161 @code{commandp} predicate so as to accept only command names:
1163 @cindex @code{commandp} example
1166 (read-command @var{prompt})
1168 (intern (completing-read @var{prompt} obarray
1174 @defun read-variable prompt &optional default
1175 @anchor{Definition of read-variable}
1176 This function reads the name of a user variable and returns it as a
1179 The argument @var{default} specifies what to return if the user enters
1180 null input. It can be a symbol or a string; if it is a string,
1181 @code{read-variable} interns it before returning it. If @var{default}
1182 is @code{nil}, that means no default has been specified; then if the
1183 user enters null input, the return value is @code{(intern "")}.
1187 (read-variable "Variable name? ")
1189 ;; @r{After evaluation of the preceding expression,}
1190 ;; @r{the following prompt appears,}
1191 ;; @r{with an empty minibuffer:}
1195 ---------- Buffer: Minibuffer ----------
1196 Variable name? @point{}
1197 ---------- Buffer: Minibuffer ----------
1202 If the user then types @kbd{fill-p @key{RET}}, @code{read-variable}
1203 returns @code{fill-prefix}.
1205 In general, @code{read-variable} is similar to @code{read-command},
1206 but uses the predicate @code{user-variable-p} instead of
1209 @cindex @code{user-variable-p} example
1212 (read-variable @var{prompt})
1215 (completing-read @var{prompt} obarray
1216 'user-variable-p t nil))
1221 See also the functions @code{read-coding-system} and
1222 @code{read-non-nil-coding-system}, in @ref{User-Chosen Coding Systems},
1223 and @code{read-input-method-name}, in @ref{Input Methods}.
1225 @node Reading File Names
1226 @subsection Reading File Names
1227 @cindex read file names
1228 @cindex prompt for file name
1230 Here is another high-level completion function, designed for reading a
1231 file name. It provides special features including automatic insertion
1232 of the default directory.
1234 @defun read-file-name prompt &optional directory default existing initial predicate
1235 This function reads a file name in the minibuffer, prompting with
1236 @var{prompt} and providing completion.
1238 If @var{existing} is non-@code{nil}, then the user must specify the name
1239 of an existing file; @key{RET} performs completion to make the name
1240 valid if possible, and then refuses to exit if it is not valid. If the
1241 value of @var{existing} is neither @code{nil} nor @code{t}, then
1242 @key{RET} also requires confirmation after completion. If
1243 @var{existing} is @code{nil}, then the name of a nonexistent file is
1246 @code{read-file-name} uses
1247 @code{minibuffer-local-filename-completion-map} as the keymap if
1248 @var{existing} is @code{nil}, and uses
1249 @code{minibuffer-local-must-match-filename-map} if @var{existing} is
1250 non-@code{nil}. @xref{Completion Commands}.
1252 The argument @var{directory} specifies the directory to use for
1253 completion of relative file names. It should be an absolute directory
1254 name. If @code{insert-default-directory} is non-@code{nil},
1255 @var{directory} is also inserted in the minibuffer as initial input.
1256 It defaults to the current buffer's value of @code{default-directory}.
1259 If you specify @var{initial}, that is an initial file name to insert
1260 in the buffer (after @var{directory}, if that is inserted). In this
1261 case, point goes at the beginning of @var{initial}. The default for
1262 @var{initial} is @code{nil}---don't insert any file name. To see what
1263 @var{initial} does, try the command @kbd{C-x C-v}. @strong{Please
1264 note:} we recommend using @var{default} rather than @var{initial} in
1267 If @var{default} is non-@code{nil}, then the function returns
1268 @var{default} if the user exits the minibuffer with the same non-empty
1269 contents that @code{read-file-name} inserted initially. The initial
1270 minibuffer contents are always non-empty if
1271 @code{insert-default-directory} is non-@code{nil}, as it is by
1272 default. @var{default} is not checked for validity, regardless of the
1273 value of @var{existing}. However, if @var{existing} is
1274 non-@code{nil}, the initial minibuffer contents should be a valid file
1275 (or directory) name. Otherwise @code{read-file-name} attempts
1276 completion if the user exits without any editing, and does not return
1277 @var{default}. @var{default} is also available through the history
1280 If @var{default} is @code{nil}, @code{read-file-name} tries to find a
1281 substitute default to use in its place, which it treats in exactly the
1282 same way as if it had been specified explicitly. If @var{default} is
1283 @code{nil}, but @var{initial} is non-@code{nil}, then the default is
1284 the absolute file name obtained from @var{directory} and
1285 @var{initial}. If both @var{default} and @var{initial} are @code{nil}
1286 and the buffer is visiting a file, @code{read-file-name} uses the
1287 absolute file name of that file as default. If the buffer is not
1288 visiting a file, then there is no default. In that case, if the user
1289 types @key{RET} without any editing, @code{read-file-name} simply
1290 returns the pre-inserted contents of the minibuffer.
1292 If the user types @key{RET} in an empty minibuffer, this function
1293 returns an empty string, regardless of the value of @var{existing}.
1294 This is, for instance, how the user can make the current buffer visit
1295 no file using @code{M-x set-visited-file-name}.
1297 If @var{predicate} is non-@code{nil}, it specifies a function of one
1298 argument that decides which file names are acceptable completion
1299 possibilities. A file name is an acceptable value if @var{predicate}
1300 returns non-@code{nil} for it.
1302 @code{read-file-name} does not automatically expand file names. You
1303 must call @code{expand-file-name} yourself if an absolute file name is
1310 (read-file-name "The file is ")
1312 ;; @r{After evaluation of the preceding expression,}
1313 ;; @r{the following appears in the minibuffer:}
1317 ---------- Buffer: Minibuffer ----------
1318 The file is /gp/gnu/elisp/@point{}
1319 ---------- Buffer: Minibuffer ----------
1324 Typing @kbd{manual @key{TAB}} results in the following:
1328 ---------- Buffer: Minibuffer ----------
1329 The file is /gp/gnu/elisp/manual.texi@point{}
1330 ---------- Buffer: Minibuffer ----------
1334 @c Wordy to avoid overfull hbox in smallbook mode.
1336 If the user types @key{RET}, @code{read-file-name} returns the file name
1337 as the string @code{"/gp/gnu/elisp/manual.texi"}.
1340 @defvar read-file-name-function
1341 If non-@code{nil}, this should be a function that accepts the same
1342 arguments as @code{read-file-name}. When @code{read-file-name} is
1343 called, it calls this function with the supplied arguments instead of
1344 doing its usual work.
1347 @defvar read-file-name-completion-ignore-case
1348 If this variable is non-@code{nil}, @code{read-file-name} ignores case
1349 when performing completion.
1352 @defun read-directory-name prompt &optional directory default existing initial
1353 This function is like @code{read-file-name} but allows only directory
1354 names as completion possibilities.
1356 If @var{default} is @code{nil} and @var{initial} is non-@code{nil},
1357 @code{read-directory-name} constructs a substitute default by
1358 combining @var{directory} (or the current buffer's default directory
1359 if @var{directory} is @code{nil}) and @var{initial}. If both
1360 @var{default} and @var{initial} are @code{nil}, this function uses
1361 @var{directory} as substitute default, or the current buffer's default
1362 directory if @var{directory} is @code{nil}.
1365 @defopt insert-default-directory
1366 This variable is used by @code{read-file-name}, and thus, indirectly,
1367 by most commands reading file names. (This includes all commands that
1368 use the code letters @samp{f} or @samp{F} in their interactive form.
1369 @xref{Interactive Codes,, Code Characters for interactive}.) Its
1370 value controls whether @code{read-file-name} starts by placing the
1371 name of the default directory in the minibuffer, plus the initial file
1372 name if any. If the value of this variable is @code{nil}, then
1373 @code{read-file-name} does not place any initial input in the
1374 minibuffer (unless you specify initial input with the @var{initial}
1375 argument). In that case, the default directory is still used for
1376 completion of relative file names, but is not displayed.
1378 If this variable is @code{nil} and the initial minibuffer contents are
1379 empty, the user may have to explicitly fetch the next history element
1380 to access a default value. If the variable is non-@code{nil}, the
1381 initial minibuffer contents are always non-empty and the user can
1382 always request a default value by immediately typing @key{RET} in an
1383 unedited minibuffer. (See above.)
1389 ;; @r{Here the minibuffer starts out with the default directory.}
1390 (let ((insert-default-directory t))
1391 (read-file-name "The file is "))
1395 ---------- Buffer: Minibuffer ----------
1396 The file is ~lewis/manual/@point{}
1397 ---------- Buffer: Minibuffer ----------
1401 ;; @r{Here the minibuffer is empty and only the prompt}
1402 ;; @r{appears on its line.}
1403 (let ((insert-default-directory nil))
1404 (read-file-name "The file is "))
1408 ---------- Buffer: Minibuffer ----------
1409 The file is @point{}
1410 ---------- Buffer: Minibuffer ----------
1415 @node Programmed Completion
1416 @subsection Programmed Completion
1417 @cindex programmed completion
1419 Sometimes it is not possible to create an alist or an obarray
1420 containing all the intended possible completions. In such a case, you
1421 can supply your own function to compute the completion of a given string.
1422 This is called @dfn{programmed completion}.
1424 To use this feature, pass a symbol with a function definition as the
1425 @var{collection} argument to @code{completing-read}. The function
1426 @code{completing-read} arranges to pass your completion function along
1427 to @code{try-completion} and @code{all-completions}, which will then let
1428 your function do all the work.
1430 The completion function should accept three arguments:
1434 The string to be completed.
1437 The predicate function to filter possible matches, or @code{nil} if
1438 none. Your function should call the predicate for each possible match,
1439 and ignore the possible match if the predicate returns @code{nil}.
1442 A flag specifying the type of operation.
1445 There are three flag values for three operations:
1449 @code{nil} specifies @code{try-completion}. The completion function
1450 should return the completion of the specified string, or @code{t} if the
1451 string is a unique and exact match already, or @code{nil} if the string
1452 matches no possibility.
1454 If the string is an exact match for one possibility, but also matches
1455 other longer possibilities, the function should return the string, not
1459 @code{t} specifies @code{all-completions}. The completion function
1460 should return a list of all possible completions of the specified
1464 @code{lambda} specifies @code{test-completion}. The completion
1465 function should return @code{t} if the specified string is an exact
1466 match for some possibility; @code{nil} otherwise.
1469 It would be consistent and clean for completion functions to allow
1470 lambda expressions (lists that are functions) as well as function
1471 symbols as @var{collection}, but this is impossible. Lists as
1472 completion tables already have other meanings, and it would be
1473 unreliable to treat one differently just because it is also a possible
1474 function. So you must arrange for any function you wish to use for
1475 completion to be encapsulated in a symbol.
1477 Emacs uses programmed completion when completing file names.
1478 @xref{File Name Completion}.
1480 @defmac dynamic-completion-table function
1481 This macro is a convenient way to write a function that can act as
1482 programmed completion function. The argument @var{function} should be
1483 a function that takes one argument, a string, and returns an alist of
1484 possible completions of it. You can think of
1485 @code{dynamic-completion-table} as a transducer between that interface
1486 and the interface for programmed completion functions.
1489 @node Yes-or-No Queries
1490 @section Yes-or-No Queries
1491 @cindex asking the user questions
1492 @cindex querying the user
1493 @cindex yes-or-no questions
1495 This section describes functions used to ask the user a yes-or-no
1496 question. The function @code{y-or-n-p} can be answered with a single
1497 character; it is useful for questions where an inadvertent wrong answer
1498 will not have serious consequences. @code{yes-or-no-p} is suitable for
1499 more momentous questions, since it requires three or four characters to
1502 If either of these functions is called in a command that was invoked
1503 using the mouse---more precisely, if @code{last-nonmenu-event}
1504 (@pxref{Command Loop Info}) is either @code{nil} or a list---then it
1505 uses a dialog box or pop-up menu to ask the question. Otherwise, it
1506 uses keyboard input. You can force use of the mouse or use of keyboard
1507 input by binding @code{last-nonmenu-event} to a suitable value around
1510 Strictly speaking, @code{yes-or-no-p} uses the minibuffer and
1511 @code{y-or-n-p} does not; but it seems best to describe them together.
1513 @defun y-or-n-p prompt
1514 This function asks the user a question, expecting input in the echo
1515 area. It returns @code{t} if the user types @kbd{y}, @code{nil} if the
1516 user types @kbd{n}. This function also accepts @key{SPC} to mean yes
1517 and @key{DEL} to mean no. It accepts @kbd{C-]} to mean ``quit,'' like
1518 @kbd{C-g}, because the question might look like a minibuffer and for
1519 that reason the user might try to use @kbd{C-]} to get out. The answer
1520 is a single character, with no @key{RET} needed to terminate it. Upper
1521 and lower case are equivalent.
1523 ``Asking the question'' means printing @var{prompt} in the echo area,
1524 followed by the string @w{@samp{(y or n) }}. If the input is not one of
1525 the expected answers (@kbd{y}, @kbd{n}, @kbd{@key{SPC}},
1526 @kbd{@key{DEL}}, or something that quits), the function responds
1527 @samp{Please answer y or n.}, and repeats the request.
1529 This function does not actually use the minibuffer, since it does not
1530 allow editing of the answer. It actually uses the echo area (@pxref{The
1531 Echo Area}), which uses the same screen space as the minibuffer. The
1532 cursor moves to the echo area while the question is being asked.
1534 The answers and their meanings, even @samp{y} and @samp{n}, are not
1535 hardwired. The keymap @code{query-replace-map} specifies them.
1536 @xref{Search and Replace}.
1538 In the following example, the user first types @kbd{q}, which is
1539 invalid. At the next prompt the user types @kbd{y}.
1543 (y-or-n-p "Do you need a lift? ")
1545 ;; @r{After evaluation of the preceding expression,}
1546 ;; @r{the following prompt appears in the echo area:}
1550 ---------- Echo area ----------
1551 Do you need a lift? (y or n)
1552 ---------- Echo area ----------
1555 ;; @r{If the user then types @kbd{q}, the following appears:}
1558 ---------- Echo area ----------
1559 Please answer y or n. Do you need a lift? (y or n)
1560 ---------- Echo area ----------
1563 ;; @r{When the user types a valid answer,}
1564 ;; @r{it is displayed after the question:}
1567 ---------- Echo area ----------
1568 Do you need a lift? (y or n) y
1569 ---------- Echo area ----------
1574 We show successive lines of echo area messages, but only one actually
1575 appears on the screen at a time.
1578 @defun y-or-n-p-with-timeout prompt seconds default-value
1579 Like @code{y-or-n-p}, except that if the user fails to answer within
1580 @var{seconds} seconds, this function stops waiting and returns
1581 @var{default-value}. It works by setting up a timer; see @ref{Timers}.
1582 The argument @var{seconds} may be an integer or a floating point number.
1585 @defun yes-or-no-p prompt
1586 This function asks the user a question, expecting input in the
1587 minibuffer. It returns @code{t} if the user enters @samp{yes},
1588 @code{nil} if the user types @samp{no}. The user must type @key{RET} to
1589 finalize the response. Upper and lower case are equivalent.
1591 @code{yes-or-no-p} starts by displaying @var{prompt} in the echo area,
1592 followed by @w{@samp{(yes or no) }}. The user must type one of the
1593 expected responses; otherwise, the function responds @samp{Please answer
1594 yes or no.}, waits about two seconds and repeats the request.
1596 @code{yes-or-no-p} requires more work from the user than
1597 @code{y-or-n-p} and is appropriate for more crucial decisions.
1603 (yes-or-no-p "Do you really want to remove everything? ")
1605 ;; @r{After evaluation of the preceding expression,}
1606 ;; @r{the following prompt appears,}
1607 ;; @r{with an empty minibuffer:}
1611 ---------- Buffer: minibuffer ----------
1612 Do you really want to remove everything? (yes or no)
1613 ---------- Buffer: minibuffer ----------
1618 If the user first types @kbd{y @key{RET}}, which is invalid because this
1619 function demands the entire word @samp{yes}, it responds by displaying
1620 these prompts, with a brief pause between them:
1624 ---------- Buffer: minibuffer ----------
1625 Please answer yes or no.
1626 Do you really want to remove everything? (yes or no)
1627 ---------- Buffer: minibuffer ----------
1632 @node Multiple Queries
1633 @section Asking Multiple Y-or-N Questions
1635 When you have a series of similar questions to ask, such as ``Do you
1636 want to save this buffer'' for each buffer in turn, you should use
1637 @code{map-y-or-n-p} to ask the collection of questions, rather than
1638 asking each question individually. This gives the user certain
1639 convenient facilities such as the ability to answer the whole series at
1642 @defun map-y-or-n-p prompter actor list &optional help action-alist no-cursor-in-echo-area
1643 This function asks the user a series of questions, reading a
1644 single-character answer in the echo area for each one.
1646 The value of @var{list} specifies the objects to ask questions about.
1647 It should be either a list of objects or a generator function. If it is
1648 a function, it should expect no arguments, and should return either the
1649 next object to ask about, or @code{nil} meaning stop asking questions.
1651 The argument @var{prompter} specifies how to ask each question. If
1652 @var{prompter} is a string, the question text is computed like this:
1655 (format @var{prompter} @var{object})
1659 where @var{object} is the next object to ask about (as obtained from
1662 If not a string, @var{prompter} should be a function of one argument
1663 (the next object to ask about) and should return the question text. If
1664 the value is a string, that is the question to ask the user. The
1665 function can also return @code{t} meaning do act on this object (and
1666 don't ask the user), or @code{nil} meaning ignore this object (and don't
1669 The argument @var{actor} says how to act on the answers that the user
1670 gives. It should be a function of one argument, and it is called with
1671 each object that the user says yes for. Its argument is always an
1672 object obtained from @var{list}.
1674 If the argument @var{help} is given, it should be a list of this form:
1677 (@var{singular} @var{plural} @var{action})
1681 where @var{singular} is a string containing a singular noun that
1682 describes the objects conceptually being acted on, @var{plural} is the
1683 corresponding plural noun, and @var{action} is a transitive verb
1684 describing what @var{actor} does.
1686 If you don't specify @var{help}, the default is @code{("object"
1687 "objects" "act on")}.
1689 Each time a question is asked, the user may enter @kbd{y}, @kbd{Y}, or
1690 @key{SPC} to act on that object; @kbd{n}, @kbd{N}, or @key{DEL} to skip
1691 that object; @kbd{!} to act on all following objects; @key{ESC} or
1692 @kbd{q} to exit (skip all following objects); @kbd{.} (period) to act on
1693 the current object and then exit; or @kbd{C-h} to get help. These are
1694 the same answers that @code{query-replace} accepts. The keymap
1695 @code{query-replace-map} defines their meaning for @code{map-y-or-n-p}
1696 as well as for @code{query-replace}; see @ref{Search and Replace}.
1698 You can use @var{action-alist} to specify additional possible answers
1699 and what they mean. It is an alist of elements of the form
1700 @code{(@var{char} @var{function} @var{help})}, each of which defines one
1701 additional answer. In this element, @var{char} is a character (the
1702 answer); @var{function} is a function of one argument (an object from
1703 @var{list}); @var{help} is a string.
1705 When the user responds with @var{char}, @code{map-y-or-n-p} calls
1706 @var{function}. If it returns non-@code{nil}, the object is considered
1707 ``acted upon,'' and @code{map-y-or-n-p} advances to the next object in
1708 @var{list}. If it returns @code{nil}, the prompt is repeated for the
1711 Normally, @code{map-y-or-n-p} binds @code{cursor-in-echo-area} while
1712 prompting. But if @var{no-cursor-in-echo-area} is non-@code{nil}, it
1715 If @code{map-y-or-n-p} is called in a command that was invoked using the
1716 mouse---more precisely, if @code{last-nonmenu-event} (@pxref{Command
1717 Loop Info}) is either @code{nil} or a list---then it uses a dialog box
1718 or pop-up menu to ask the question. In this case, it does not use
1719 keyboard input or the echo area. You can force use of the mouse or use
1720 of keyboard input by binding @code{last-nonmenu-event} to a suitable
1721 value around the call.
1723 The return value of @code{map-y-or-n-p} is the number of objects acted on.
1726 @node Reading a Password
1727 @section Reading a Password
1728 @cindex passwords, reading
1730 To read a password to pass to another program, you can use the
1731 function @code{read-passwd}.
1733 @defun read-passwd prompt &optional confirm default
1734 This function reads a password, prompting with @var{prompt}. It does
1735 not echo the password as the user types it; instead, it echoes @samp{.}
1736 for each character in the password.
1738 The optional argument @var{confirm}, if non-@code{nil}, says to read the
1739 password twice and insist it must be the same both times. If it isn't
1740 the same, the user has to type it over and over until the last two
1743 The optional argument @var{default} specifies the default password to
1744 return if the user enters empty input. If @var{default} is @code{nil},
1745 then @code{read-passwd} returns the null string in that case.
1748 @node Minibuffer Commands
1749 @section Minibuffer Commands
1751 This section describes some commands meant for use in the
1754 @deffn Command exit-minibuffer
1755 This command exits the active minibuffer. It is normally bound to
1756 keys in minibuffer local keymaps.
1759 @deffn Command self-insert-and-exit
1760 This command exits the active minibuffer after inserting the last
1761 character typed on the keyboard (found in @code{last-command-char};
1762 @pxref{Command Loop Info}).
1765 @deffn Command previous-history-element n
1766 This command replaces the minibuffer contents with the value of the
1767 @var{n}th previous (older) history element.
1770 @deffn Command next-history-element n
1771 This command replaces the minibuffer contents with the value of the
1772 @var{n}th more recent history element.
1775 @deffn Command previous-matching-history-element pattern n
1776 This command replaces the minibuffer contents with the value of the
1777 @var{n}th previous (older) history element that matches @var{pattern} (a
1778 regular expression).
1781 @deffn Command next-matching-history-element pattern n
1782 This command replaces the minibuffer contents with the value of the
1783 @var{n}th next (newer) history element that matches @var{pattern} (a
1784 regular expression).
1787 @node Minibuffer Windows
1788 @section Minibuffer Windows
1789 @cindex minibuffer windows
1791 These functions access and select minibuffer windows
1792 and test whether they are active.
1794 @defun active-minibuffer-window
1795 This function returns the currently active minibuffer window, or
1796 @code{nil} if none is currently active.
1799 @defun minibuffer-window &optional frame
1800 @anchor{Definition of minibuffer-window}
1801 This function returns the minibuffer window used for frame @var{frame}.
1802 If @var{frame} is @code{nil}, that stands for the current frame. Note
1803 that the minibuffer window used by a frame need not be part of that
1804 frame---a frame that has no minibuffer of its own necessarily uses some
1805 other frame's minibuffer window.
1808 @defun set-minibuffer-window window
1809 This function specifies @var{window} as the minibuffer window to use.
1810 This affects where the minibuffer is displayed if you put text in it
1811 without invoking the usual minibuffer commands. It has no effect on
1812 the usual minibuffer input functions because they all start by
1813 choosing the minibuffer window according to the current frame.
1817 @defun window-minibuffer-p &optional window
1818 This function returns non-@code{nil} if @var{window} is a minibuffer
1820 @var{window} defaults to the selected window.
1823 It is not correct to determine whether a given window is a minibuffer by
1824 comparing it with the result of @code{(minibuffer-window)}, because
1825 there can be more than one minibuffer window if there is more than one
1828 @defun minibuffer-window-active-p window
1829 This function returns non-@code{nil} if @var{window}, assumed to be
1830 a minibuffer window, is currently active.
1833 @node Minibuffer Contents
1834 @section Minibuffer Contents
1836 These functions access the minibuffer prompt and contents.
1838 @defun minibuffer-prompt
1839 This function returns the prompt string of the currently active
1840 minibuffer. If no minibuffer is active, it returns @code{nil}.
1843 @defun minibuffer-prompt-end
1844 This function returns the current
1845 position of the end of the minibuffer prompt, if a minibuffer is
1846 current. Otherwise, it returns the minimum valid buffer position.
1849 @defun minibuffer-prompt-width
1850 This function returns the current display-width of the minibuffer
1851 prompt, if a minibuffer is current. Otherwise, it returns zero.
1854 @defun minibuffer-contents
1855 This function returns the editable
1856 contents of the minibuffer (that is, everything except the prompt) as
1857 a string, if a minibuffer is current. Otherwise, it returns the
1858 entire contents of the current buffer.
1861 @defun minibuffer-contents-no-properties
1862 This is like @code{minibuffer-contents}, except that it does not copy text
1863 properties, just the characters themselves. @xref{Text Properties}.
1866 @defun minibuffer-completion-contents
1867 This is like @code{minibuffer-contents}, except that it returns only
1868 the contents before point. That is the part that completion commands
1869 operate on. @xref{Minibuffer Completion}.
1872 @defun delete-minibuffer-contents
1873 This function erases the editable contents of the minibuffer (that is,
1874 everything except the prompt), if a minibuffer is current. Otherwise,
1875 it erases the entire current buffer.
1878 @node Recursive Mini
1879 @section Recursive Minibuffers
1880 @cindex recursive minibuffers
1882 These functions and variables deal with recursive minibuffers
1883 (@pxref{Recursive Editing}):
1885 @defun minibuffer-depth
1886 This function returns the current depth of activations of the
1887 minibuffer, a nonnegative integer. If no minibuffers are active, it
1891 @defopt enable-recursive-minibuffers
1892 If this variable is non-@code{nil}, you can invoke commands (such as
1893 @code{find-file}) that use minibuffers even while the minibuffer window
1894 is active. Such invocation produces a recursive editing level for a new
1895 minibuffer. The outer-level minibuffer is invisible while you are
1896 editing the inner one.
1898 If this variable is @code{nil}, you cannot invoke minibuffer
1899 commands when the minibuffer window is active, not even if you switch to
1900 another window to do it.
1904 If a command name has a property @code{enable-recursive-minibuffers}
1905 that is non-@code{nil}, then the command can use the minibuffer to read
1906 arguments even if it is invoked from the minibuffer. A command can
1907 also achieve this by binding @code{enable-recursive-minibuffers}
1908 to @code{t} in the interactive declaration (@pxref{Using Interactive}).
1909 The minibuffer command @code{next-matching-history-element} (normally
1910 @kbd{M-s} in the minibuffer) does the latter.
1912 @node Minibuffer Misc
1913 @section Minibuffer Miscellany
1915 @defun minibufferp &optional buffer-or-name
1916 This function returns non-@code{nil} if @var{buffer-or-name} is a
1917 minibuffer. If @var{buffer-or-name} is omitted, it tests the current
1921 @defvar minibuffer-setup-hook
1922 This is a normal hook that is run whenever the minibuffer is entered.
1926 @defvar minibuffer-exit-hook
1927 This is a normal hook that is run whenever the minibuffer is exited.
1931 @defvar minibuffer-help-form
1932 @anchor{Definition of minibuffer-help-form}
1933 The current value of this variable is used to rebind @code{help-form}
1934 locally inside the minibuffer (@pxref{Help Functions}).
1937 @defvar minibuffer-scroll-window
1938 @anchor{Definition of minibuffer-scroll-window}
1939 If the value of this variable is non-@code{nil}, it should be a window
1940 object. When the function @code{scroll-other-window} is called in the
1941 minibuffer, it scrolls this window.
1944 @defun minibuffer-selected-window
1945 This function returns the window which was selected when the
1946 minibuffer was entered. If selected window is not a minibuffer
1947 window, it returns @code{nil}.
1950 @defopt max-mini-window-height
1951 This variable specifies the maximum height for resizing minibuffer
1952 windows. If a float, it specifies a fraction of the height of the
1953 frame. If an integer, it specifies a number of lines.
1956 @defun minibuffer-message string
1957 This function displays @var{string} temporarily at the end of the
1958 minibuffer text, for two seconds, or until the next input event
1959 arrives, whichever comes first.
1963 arch-tag: bba7f945-9078-477f-a2ce-18818a6e1218