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-dups
453 This function adds a new element @var{newelt} to the history list
454 stored in the variable @var{history-var}, and returns the updated
455 history list. By default, the list length is limited by the value
456 specified by @code{history-length} (described below), but the optional
457 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, unless
462 @code{history-delete-duplicates} is @code{nil} or the second optional
463 argument of this function @var{keep-dups} is non-@code{nil}.
466 @defvar history-length
467 The value of this variable specifies the maximum length for all
468 history lists that don't specify their own maximum lengths. If the
469 value is @code{t}, that means there no maximum (don't delete old
470 elements). The value of @code{history-length} property of the history
471 list variable's symbol, if set, overrides this variable for that
472 particular history list.
475 @defvar history-delete-duplicates
476 If the value of this variable is @code{t}, that means when adding a
477 new history element, all previous identical elements are deleted.
480 Here are some of the standard minibuffer history list variables:
482 @defvar minibuffer-history
483 The default history list for minibuffer history input.
486 @defvar query-replace-history
487 A history list for arguments to @code{query-replace} (and similar
488 arguments to other commands).
491 @defvar file-name-history
492 A history list for file-name arguments.
495 @defvar buffer-name-history
496 A history list for buffer-name arguments.
499 @defvar regexp-history
500 A history list for regular expression arguments.
503 @defvar extended-command-history
504 A history list for arguments that are names of extended commands.
507 @defvar shell-command-history
508 A history list for arguments that are shell commands.
511 @defvar read-expression-history
512 A history list for arguments that are Lisp expressions to evaluate.
516 @section Initial Input
518 Several of the functions for minibuffer input have an argument called
519 @var{initial} or @var{initial-contents}. This is a mostly-deprecated
520 feature for specifiying that the minibuffer should start out with
521 certain text, instead of empty as usual.
523 If @var{initial} is a string, the minibuffer starts out containing the
524 text of the string, with point at the end, when the user starts to
525 edit the text. If the user simply types @key{RET} to exit the
526 minibuffer, it will use the initial input string to determine the
529 @strong{We discourage use of a non-@code{nil} value for
530 @var{initial}}, because initial input is an intrusive interface.
531 History lists and default values provide a much more convenient method
532 to offer useful default inputs to the user.
534 There is just one situation where you should specify a string for an
535 @var{initial} argument. This is when you specify a cons cell for the
536 @var{hist} or @var{history} argument. @xref{Minibuffer History}.
538 @var{initial} can also be a cons cell of the form @code{(@var{string}
539 . @var{position})}. This means to insert @var{string} in the
540 minibuffer but put point at @var{position} within the string's text.
542 As a historical accident, @var{position} was implemented
543 inconsistently in different functions. In @code{completing-read},
544 @var{position}'s value is interpreted as origin-zero; that is, a value
545 of 0 means the beginning of the string, 1 means after the first
546 character, etc. In @code{read-minibuffer}, and the other
547 non-completion minibuffer input functions that support this argument,
548 1 means the beginning of the string 2 means after the first character,
551 Use of a cons cell as the value for @var{initial} arguments is
552 deprecated in user code.
558 @dfn{Completion} is a feature that fills in the rest of a name
559 starting from an abbreviation for it. Completion works by comparing the
560 user's input against a list of valid names and determining how much of
561 the name is determined uniquely by what the user has typed. For
562 example, when you type @kbd{C-x b} (@code{switch-to-buffer}) and then
563 type the first few letters of the name of the buffer to which you wish
564 to switch, and then type @key{TAB} (@code{minibuffer-complete}), Emacs
565 extends the name as far as it can.
567 Standard Emacs commands offer completion for names of symbols, files,
568 buffers, and processes; with the functions in this section, you can
569 implement completion for other kinds of names.
571 The @code{try-completion} function is the basic primitive for
572 completion: it returns the longest determined completion of a given
573 initial string, with a given set of strings to match against.
575 The function @code{completing-read} provides a higher-level interface
576 for completion. A call to @code{completing-read} specifies how to
577 determine the list of valid names. The function then activates the
578 minibuffer with a local keymap that binds a few keys to commands useful
579 for completion. Other functions provide convenient simple interfaces
580 for reading certain kinds of names with completion.
583 * Basic Completion:: Low-level functions for completing strings.
584 (These are too low level to use the minibuffer.)
585 * Minibuffer Completion:: Invoking the minibuffer with completion.
586 * Completion Commands:: Minibuffer commands that do completion.
587 * High-Level Completion:: Convenient special cases of completion
588 (reading buffer name, file name, etc.)
589 * Reading File Names:: Using completion to read file names.
590 * Programmed Completion:: Writing your own completion-function.
593 @node Basic Completion
594 @subsection Basic Completion Functions
596 The completion functions @code{try-completion},
597 @code{all-completions} and @code{test-completion} have nothing in
598 themselves to do with minibuffers. We describe them in this chapter
599 so as to keep them near the higher-level completion features that do
602 If you store a completion alist in a variable, you should mark the
603 variable as ``risky'' with a non-@code{nil}
604 @code{risky-local-variable} property.
606 @defun try-completion string collection &optional predicate
607 This function returns the longest common substring of all possible
608 completions of @var{string} in @var{collection}. The value of
609 @var{collection} must be a list of strings or symbols, an alist, an
610 obarray, a hash table, or a function that implements a virtual set of
613 Completion compares @var{string} against each of the permissible
614 completions specified by @var{collection}; if the beginning of the
615 permissible completion equals @var{string}, it matches. If no permissible
616 completions match, @code{try-completion} returns @code{nil}. If only
617 one permissible completion matches, and the match is exact, then
618 @code{try-completion} returns @code{t}. Otherwise, the value is the
619 longest initial sequence common to all the permissible completions that
622 If @var{collection} is an alist (@pxref{Association Lists}), the
623 permissible completions are the elements of the alist that are either
624 strings, symbols, or conses whose @sc{car} is a string or symbol.
625 Symbols are converted to strings using @code{symbol-name}.
626 Other elements of the alist are ignored. (Remember that in Emacs Lisp,
627 the elements of alists do not @emph{have} to be conses.) As all
628 elements of the alist can be strings, this case actually includes
629 lists of strings or symbols, even though we usually do not think of
630 such lists as alists.
632 @cindex obarray in completion
633 If @var{collection} is an obarray (@pxref{Creating Symbols}), the names
634 of all symbols in the obarray form the set of permissible completions. The
635 global variable @code{obarray} holds an obarray containing the names of
636 all interned Lisp symbols.
638 Note that the only valid way to make a new obarray is to create it
639 empty and then add symbols to it one by one using @code{intern}.
640 Also, you cannot intern a given symbol in more than one obarray.
642 If @var{collection} is a hash table, then the keys that are strings
643 are the possible completions. Other keys are ignored.
645 You can also use a symbol that is a function as @var{collection}. Then
646 the function is solely responsible for performing completion;
647 @code{try-completion} returns whatever this function returns. The
648 function is called with three arguments: @var{string}, @var{predicate}
649 and @code{nil}. (The reason for the third argument is so that the same
650 function can be used in @code{all-completions} and do the appropriate
651 thing in either case.) @xref{Programmed Completion}.
653 If the argument @var{predicate} is non-@code{nil}, then it must be a
654 function of one argument, unless @var{collection} is a hash table, in
655 which case it should be a function of two arguments. It is used to
656 test each possible match, and the match is accepted only if
657 @var{predicate} returns non-@code{nil}. The argument given to
658 @var{predicate} is either a string or a cons cell (the @sc{car} of
659 which is a string) from the alist, or a symbol (@emph{not} a symbol
660 name) from the obarray. If @var{collection} is a hash table,
661 @var{predicate} is called with two arguments, the string key and the
664 In addition, to be acceptable, a completion must also match all the
665 regular expressions in @code{completion-regexp-list}. (Unless
666 @var{collection} is a function, in which case that function has to
667 handle @code{completion-regexp-list} itself.)
669 In the first of the following examples, the string @samp{foo} is
670 matched by three of the alist @sc{car}s. All of the matches begin with
671 the characters @samp{fooba}, so that is the result. In the second
672 example, there is only one possible match, and it is exact, so the value
679 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)))
684 (try-completion "foo" '(("barfoo" 2) ("foo" 3)))
689 In the following example, numerous symbols begin with the characters
690 @samp{forw}, and all of them begin with the word @samp{forward}. In
691 most of the symbols, this is followed with a @samp{-}, but not in all,
692 so no more than @samp{forward} can be completed.
696 (try-completion "forw" obarray)
701 Finally, in the following example, only two of the three possible
702 matches pass the predicate @code{test} (the string @samp{foobaz} is
703 too short). Both of those begin with the string @samp{foobar}.
708 (> (length (car s)) 6))
714 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
721 @defun all-completions string collection &optional predicate nospace
722 This function returns a list of all possible completions of
723 @var{string}. The arguments to this function (aside from
724 @var{nospace}) are the same as those of @code{try-completion}. Also,
725 this function uses @code{completion-regexp-list} in the same way that
726 @code{try-completion} does. The optional argument @var{nospace} only
727 matters if @var{string} is the empty string. In that case, if
728 @var{nospace} is non-@code{nil}, completions that start with a space
731 If @var{collection} is a function, it is called with three arguments:
732 @var{string}, @var{predicate} and @code{t}; then @code{all-completions}
733 returns whatever the function returns. @xref{Programmed Completion}.
735 Here is an example, using the function @code{test} shown in the
736 example for @code{try-completion}:
741 (> (length (car s)) 6))
748 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
750 @result{} ("foobar1" "foobar2")
755 @defun test-completion string collection &optional predicate
756 @anchor{Definition of test-completion}
757 This function returns non-@code{nil} if @var{string} is a valid
758 completion possibility specified by @var{collection} and
759 @var{predicate}. The arguments are the same as in
760 @code{try-completion}. For instance, if @var{collection} is a list of
761 strings, this is true if @var{string} appears in the list and
762 @var{predicate} is satisfied.
764 @code{test-completion} uses @code{completion-regexp-list} in the same
765 way that @code{try-completion} does.
767 If @var{predicate} is non-@code{nil} and if @var{collection} contains
768 several strings that are equal to each other, as determined by
769 @code{compare-strings} according to @code{completion-ignore-case},
770 then @var{predicate} should accept either all or none of them.
771 Otherwise, the return value of @code{test-completion} is essentially
774 If @var{collection} is a function, it is called with three arguments,
775 the values @var{string}, @var{predicate} and @code{lambda}; whatever
776 it returns, @code{test-completion} returns in turn.
779 @defvar completion-ignore-case
780 If the value of this variable is non-@code{nil}, Emacs does not
781 consider case significant in completion.
784 @defvar completion-regexp-list
785 This is a list of regular expressions. The completion functions only
786 consider a completion acceptable if it matches all regular expressions
787 in this list, with @code{case-fold-search} (@pxref{Searching and Case})
788 bound to the value of @code{completion-ignore-case}.
791 @defmac lazy-completion-table var fun
792 This macro provides a way to initialize the variable @var{var} as a
793 collection for completion in a lazy way, not computing its actual
794 contents until they are first needed. You use this macro to produce a
795 value that you store in @var{var}. The actual computation of the
796 proper value is done the first time you do completion using @var{var}.
797 It is done by calling @var{fun} with no arguments. The
798 value @var{fun} returns becomes the permanent value of @var{var}.
800 Here is an example of use:
803 (defvar foo (lazy-completion-table foo make-my-alist))
807 @node Minibuffer Completion
808 @subsection Completion and the Minibuffer
810 This section describes the basic interface for reading from the
811 minibuffer with completion.
813 @defun completing-read prompt collection &optional predicate require-match initial hist default inherit-input-method
814 This function reads a string in the minibuffer, assisting the user by
815 providing completion. It activates the minibuffer with prompt
816 @var{prompt}, which must be a string.
818 The actual completion is done by passing @var{collection} and
819 @var{predicate} to the function @code{try-completion}. This happens
820 in certain commands bound in the local keymaps used for completion.
821 Some of these commands also call @code{test-completion}. Thus, if
822 @var{predicate} is non-@code{nil}, it should be compatible with
823 @var{collection} and @code{completion-ignore-case}. @xref{Definition
826 If @var{require-match} is @code{nil}, the exit commands work regardless
827 of the input in the minibuffer. If @var{require-match} is @code{t}, the
828 usual minibuffer exit commands won't exit unless the input completes to
829 an element of @var{collection}. If @var{require-match} is neither
830 @code{nil} nor @code{t}, then the exit commands won't exit unless the
831 input already in the buffer matches an element of @var{collection}.
833 However, empty input is always permitted, regardless of the value of
834 @var{require-match}; in that case, @code{completing-read} returns
835 @var{default}, or @code{""}, if @var{default} is @code{nil}. The
836 value of @var{default} (if non-@code{nil}) is also available to the
837 user through the history commands.
839 The function @code{completing-read} uses
840 @code{minibuffer-local-completion-map} as the keymap if
841 @var{require-match} is @code{nil}, and uses
842 @code{minibuffer-local-must-match-map} if @var{require-match} is
843 non-@code{nil}. @xref{Completion Commands}.
845 The argument @var{hist} specifies which history list variable to use for
846 saving the input and for minibuffer history commands. It defaults to
847 @code{minibuffer-history}. @xref{Minibuffer History}.
849 The argument @var{initial} is mostly deprecated; we recommend using a
850 non-@code{nil} value only in conjunction with specifying a cons cell
851 for @var{hist}. @xref{Initial Input}. For default input, use
852 @var{default} instead.
854 If the argument @var{inherit-input-method} is non-@code{nil}, then the
855 minibuffer inherits the current input method (@pxref{Input
856 Methods}) and the setting of @code{enable-multibyte-characters}
857 (@pxref{Text Representations}) from whichever buffer was current before
858 entering the minibuffer.
860 If the built-in variable @code{completion-ignore-case} is
861 non-@code{nil}, completion ignores case when comparing the input
862 against the possible matches. @xref{Basic Completion}. In this mode
863 of operation, @var{predicate} must also ignore case, or you will get
866 Here's an example of using @code{completing-read}:
872 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
877 ;; @r{After evaluation of the preceding expression,}
878 ;; @r{the following appears in the minibuffer:}
880 ---------- Buffer: Minibuffer ----------
881 Complete a foo: fo@point{}
882 ---------- Buffer: Minibuffer ----------
887 If the user then types @kbd{@key{DEL} @key{DEL} b @key{RET}},
888 @code{completing-read} returns @code{barfoo}.
890 The @code{completing-read} function binds variables to pass
891 information to the commands that actually do completion.
892 They are described in the following section.
895 @node Completion Commands
896 @subsection Minibuffer Commands that Do Completion
898 This section describes the keymaps, commands and user options used
899 in the minibuffer to do completion. The description refers to the
900 situation when Partial Completion mode is disabled (as it is by
901 default). When enabled, this minor mode uses its own alternatives to
902 some of the commands described below. @xref{Completion Options,,,
903 emacs, The GNU Emacs Manual}, for a short description of Partial
906 @defvar minibuffer-completion-table
907 The value of this variable is the collection used for completion in
908 the minibuffer. This is the global variable that contains what
909 @code{completing-read} passes to @code{try-completion}. It is used by
910 minibuffer completion commands such as @code{minibuffer-complete-word}.
913 @defvar minibuffer-completion-predicate
914 This variable's value is the predicate that @code{completing-read}
915 passes to @code{try-completion}. The variable is also used by the other
916 minibuffer completion functions.
919 @defvar minibuffer-completion-confirm
920 When the value of this variable is non-@code{nil}, Emacs asks for
921 confirmation of a completion before exiting the minibuffer.
922 @code{completing-read} binds this variable, and the function
923 @code{minibuffer-complete-and-exit} checks the value before exiting.
926 @deffn Command minibuffer-complete-word
927 This function completes the minibuffer contents by at most a single
928 word. Even if the minibuffer contents have only one completion,
929 @code{minibuffer-complete-word} does not add any characters beyond the
930 first character that is not a word constituent. @xref{Syntax Tables}.
933 @deffn Command minibuffer-complete
934 This function completes the minibuffer contents as far as possible.
937 @deffn Command minibuffer-complete-and-exit
938 This function completes the minibuffer contents, and exits if
939 confirmation is not required, i.e., if
940 @code{minibuffer-completion-confirm} is @code{nil}. If confirmation
941 @emph{is} required, it is given by repeating this command
942 immediately---the command is programmed to work without confirmation
943 when run twice in succession.
946 @deffn Command minibuffer-completion-help
947 This function creates a list of the possible completions of the
948 current minibuffer contents. It works by calling @code{all-completions}
949 using the value of the variable @code{minibuffer-completion-table} as
950 the @var{collection} argument, and the value of
951 @code{minibuffer-completion-predicate} as the @var{predicate} argument.
952 The list of completions is displayed as text in a buffer named
953 @samp{*Completions*}.
956 @defun display-completion-list completions &optional common-substring
957 This function displays @var{completions} to the stream in
958 @code{standard-output}, usually a buffer. (@xref{Read and Print}, for more
959 information about streams.) The argument @var{completions} is normally
960 a list of completions just returned by @code{all-completions}, but it
961 does not have to be. Each element may be a symbol or a string, either
962 of which is simply printed. It can also be a list of two strings,
963 which is printed as if the strings were concatenated. The first of
964 the two strings is the actual completion, the second string serves as
967 The argument @var{common-substring} is the prefix that is common to
968 all the completions. With normal Emacs completion, it is usually the
969 same as the string that was completed. @code{display-completion-list}
970 uses this to highlight text in the completion list for better visual
971 feedback. This is not needed in the minibuffer; for minibuffer
972 completion, you can pass @code{nil}.
974 This function is called by @code{minibuffer-completion-help}. The
975 most common way to use it is together with
976 @code{with-output-to-temp-buffer}, like this:
979 (with-output-to-temp-buffer "*Completions*"
980 (display-completion-list
981 (all-completions (buffer-string) my-alist)
986 @defopt completion-auto-help
987 If this variable is non-@code{nil}, the completion commands
988 automatically display a list of possible completions whenever nothing
989 can be completed because the next character is not uniquely determined.
992 @defvar minibuffer-local-completion-map
993 @code{completing-read} uses this value as the local keymap when an
994 exact match of one of the completions is not required. By default, this
995 keymap makes the following bindings:
999 @code{minibuffer-completion-help}
1002 @code{minibuffer-complete-word}
1005 @code{minibuffer-complete}
1009 with other characters bound as in @code{minibuffer-local-map}
1010 (@pxref{Definition of minibuffer-local-map}).
1013 @defvar minibuffer-local-must-match-map
1014 @code{completing-read} uses this value as the local keymap when an
1015 exact match of one of the completions is required. Therefore, no keys
1016 are bound to @code{exit-minibuffer}, the command that exits the
1017 minibuffer unconditionally. By default, this keymap makes the following
1022 @code{minibuffer-completion-help}
1025 @code{minibuffer-complete-word}
1028 @code{minibuffer-complete}
1031 @code{minibuffer-complete-and-exit}
1034 @code{minibuffer-complete-and-exit}
1038 with other characters bound as in @code{minibuffer-local-map}.
1041 @defvar minibuffer-local-filename-completion-map
1042 This is like @code{minibuffer-local-completion-map}
1043 except that it does not bind @key{SPC}. This keymap is used by the
1044 function @code{read-file-name}.
1047 @defvar minibuffer-local-must-match-filename-map
1048 This is like @code{minibuffer-local-must-match-map}
1049 except that it does not bind @key{SPC}. This keymap is used by the
1050 function @code{read-file-name}.
1053 @node High-Level Completion
1054 @subsection High-Level Completion Functions
1056 This section describes the higher-level convenient functions for
1057 reading certain sorts of names with completion.
1059 In most cases, you should not call these functions in the middle of a
1060 Lisp function. When possible, do all minibuffer input as part of
1061 reading the arguments for a command, in the @code{interactive}
1062 specification. @xref{Defining Commands}.
1064 @defun read-buffer prompt &optional default existing
1065 This function reads the name of a buffer and returns it as a string.
1066 The argument @var{default} is the default name to use, the value to
1067 return if the user exits with an empty minibuffer. If non-@code{nil},
1068 it should be a string or a buffer. It is mentioned in the prompt, but
1069 is not inserted in the minibuffer as initial input.
1071 The argument @var{prompt} should be a string ending with a colon and a
1072 space. If @var{default} is non-@code{nil}, the function inserts it in
1073 @var{prompt} before the colon to follow the convention for reading from
1074 the minibuffer with a default value (@pxref{Programming Tips}).
1076 If @var{existing} is non-@code{nil}, then the name specified must be
1077 that of an existing buffer. The usual commands to exit the minibuffer
1078 do not exit if the text is not valid, and @key{RET} does completion to
1079 attempt to find a valid name. If @var{existing} is neither @code{nil}
1080 nor @code{t}, confirmation is required after completion. (However,
1081 @var{default} is not checked for validity; it is returned, whatever it
1082 is, if the user exits with the minibuffer empty.)
1084 In the following example, the user enters @samp{minibuffer.t}, and
1085 then types @key{RET}. The argument @var{existing} is @code{t}, and the
1086 only buffer name starting with the given input is
1087 @samp{minibuffer.texi}, so that name is the value.
1090 (read-buffer "Buffer name: " "foo" t)
1092 ;; @r{After evaluation of the preceding expression,}
1093 ;; @r{the following prompt appears,}
1094 ;; @r{with an empty minibuffer:}
1098 ---------- Buffer: Minibuffer ----------
1099 Buffer name (default foo): @point{}
1100 ---------- Buffer: Minibuffer ----------
1104 ;; @r{The user types @kbd{minibuffer.t @key{RET}}.}
1105 @result{} "minibuffer.texi"
1110 @defvar read-buffer-function
1111 This variable specifies how to read buffer names. For example, if you
1112 set this variable to @code{iswitchb-read-buffer}, all Emacs commands
1113 that call @code{read-buffer} to read a buffer name will actually use the
1114 @code{iswitchb} package to read it.
1117 @defun read-command prompt &optional default
1118 This function reads the name of a command and returns it as a Lisp
1119 symbol. The argument @var{prompt} is used as in
1120 @code{read-from-minibuffer}. Recall that a command is anything for
1121 which @code{commandp} returns @code{t}, and a command name is a symbol
1122 for which @code{commandp} returns @code{t}. @xref{Interactive Call}.
1124 The argument @var{default} specifies what to return if the user enters
1125 null input. It can be a symbol or a string; if it is a string,
1126 @code{read-command} interns it before returning it. If @var{default} is
1127 @code{nil}, that means no default has been specified; then if the user
1128 enters null input, the return value is @code{(intern "")}, that is, a
1129 symbol whose name is an empty string.
1132 (read-command "Command name? ")
1135 ;; @r{After evaluation of the preceding expression,}
1136 ;; @r{the following prompt appears with an empty minibuffer:}
1140 ---------- Buffer: Minibuffer ----------
1142 ---------- Buffer: Minibuffer ----------
1147 If the user types @kbd{forward-c @key{RET}}, then this function returns
1148 @code{forward-char}.
1150 The @code{read-command} function is a simplified interface to
1151 @code{completing-read}. It uses the variable @code{obarray} so as to
1152 complete in the set of extant Lisp symbols, and it uses the
1153 @code{commandp} predicate so as to accept only command names:
1155 @cindex @code{commandp} example
1158 (read-command @var{prompt})
1160 (intern (completing-read @var{prompt} obarray
1166 @defun read-variable prompt &optional default
1167 @anchor{Definition of read-variable}
1168 This function reads the name of a user variable and returns it as a
1171 The argument @var{default} specifies what to return if the user enters
1172 null input. It can be a symbol or a string; if it is a string,
1173 @code{read-variable} interns it before returning it. If @var{default}
1174 is @code{nil}, that means no default has been specified; then if the
1175 user enters null input, the return value is @code{(intern "")}.
1179 (read-variable "Variable name? ")
1181 ;; @r{After evaluation of the preceding expression,}
1182 ;; @r{the following prompt appears,}
1183 ;; @r{with an empty minibuffer:}
1187 ---------- Buffer: Minibuffer ----------
1188 Variable name? @point{}
1189 ---------- Buffer: Minibuffer ----------
1194 If the user then types @kbd{fill-p @key{RET}}, @code{read-variable}
1195 returns @code{fill-prefix}.
1197 This function is similar to @code{read-command}, but uses the
1198 predicate @code{user-variable-p} instead of @code{commandp}:
1200 @cindex @code{user-variable-p} example
1203 (read-variable @var{prompt})
1206 (completing-read @var{prompt} obarray
1207 'user-variable-p t nil))
1212 See also the functions @code{read-coding-system} and
1213 @code{read-non-nil-coding-system}, in @ref{User-Chosen Coding Systems},
1214 and @code{read-input-method-name}, in @ref{Input Methods}.
1216 @node Reading File Names
1217 @subsection Reading File Names
1219 Here is another high-level completion function, designed for reading a
1220 file name. It provides special features including automatic insertion
1221 of the default directory.
1223 @defun read-file-name prompt &optional directory default existing initial predicate
1224 This function reads a file name in the minibuffer, prompting with
1225 @var{prompt} and providing completion.
1227 If @var{existing} is non-@code{nil}, then the user must specify the name
1228 of an existing file; @key{RET} performs completion to make the name
1229 valid if possible, and then refuses to exit if it is not valid. If the
1230 value of @var{existing} is neither @code{nil} nor @code{t}, then
1231 @key{RET} also requires confirmation after completion. If
1232 @var{existing} is @code{nil}, then the name of a nonexistent file is
1235 The function @code{read-file-name} uses
1236 @code{minibuffer-local-filename-completion-map} as the keymap if
1237 @var{existing} is @code{nil}, and uses
1238 @code{minibuffer-local-must-match-filename-map} if @var{existing} is
1239 non-@code{nil}. @xref{Completion Commands}.
1241 The argument @var{directory} specifies the directory to use for
1242 completion of relative file names. It should be an absolute directory
1243 name. If @code{insert-default-directory} is non-@code{nil},
1244 @var{directory} is also inserted in the minibuffer as initial input.
1245 It defaults to the current buffer's value of @code{default-directory}.
1248 If you specify @var{initial}, that is an initial file name to insert
1249 in the buffer (after @var{directory}, if that is inserted). In this
1250 case, point goes at the beginning of @var{initial}. The default for
1251 @var{initial} is @code{nil}---don't insert any file name. To see what
1252 @var{initial} does, try the command @kbd{C-x C-v}. @strong{Please
1253 note:} we recommend using @var{default} rather than @var{initial} in
1256 If @var{default} is non-@code{nil}, then the function returns
1257 @var{default} if the user exits the minibuffer with the same non-empty
1258 contents that @code{read-file-name} inserted initially. The initial
1259 minibuffer contents are always non-empty if
1260 @code{insert-default-directory} is non-@code{nil}, as it is by
1261 default. @var{default} is not checked for validity, regardless of the
1262 value of @var{existing}. However, if @var{existing} is
1263 non-@code{nil}, the initial minibuffer contents should be a valid file
1264 (or directory) name. Otherwise @code{read-file-name} attempts
1265 completion if the user exits without any editing, and does not return
1266 @var{default}. @var{default} is also available through the history
1269 If @var{default} is @code{nil}, @code{read-file-name} tries to find a
1270 substitute default to use in its place, which it treats in exactly the
1271 same way as if it had been specified explicitly. If @var{default} is
1272 @code{nil}, but @var{initial} is non-@code{nil}, then the default is
1273 the absolute file name obtained from @var{directory} and
1274 @var{initial}. If both @var{default} and @var{initial} are @code{nil}
1275 and the buffer is visiting a file, @code{read-file-name} uses the
1276 absolute file name of that file as default. If the buffer is not
1277 visiting a file, then there is no default. In that case, if the user
1278 types @key{RET} without any editing, @code{read-file-name} simply
1279 returns the pre-inserted contents of the minibuffer.
1281 If the user types @key{RET} in an empty minibuffer, this function
1282 returns an empty string, regardless of the value of @var{existing}.
1283 This is, for instance, how the user can make the current buffer visit
1284 no file using @code{M-x set-visited-file-name}.
1286 If @var{predicate} is non-@code{nil}, it specifies a function of one
1287 argument that decides which file names are acceptable completion
1288 possibilities. A file name is an acceptable value if @var{predicate}
1289 returns non-@code{nil} for it.
1291 @code{read-file-name} does not automatically expand file names. You
1292 must call @code{expand-file-name} yourself if an absolute file name is
1299 (read-file-name "The file is ")
1301 ;; @r{After evaluation of the preceding expression,}
1302 ;; @r{the following appears in the minibuffer:}
1306 ---------- Buffer: Minibuffer ----------
1307 The file is /gp/gnu/elisp/@point{}
1308 ---------- Buffer: Minibuffer ----------
1313 Typing @kbd{manual @key{TAB}} results in the following:
1317 ---------- Buffer: Minibuffer ----------
1318 The file is /gp/gnu/elisp/manual.texi@point{}
1319 ---------- Buffer: Minibuffer ----------
1323 @c Wordy to avoid overfull hbox in smallbook mode.
1325 If the user types @key{RET}, @code{read-file-name} returns the file name
1326 as the string @code{"/gp/gnu/elisp/manual.texi"}.
1329 @defvar read-file-name-function
1330 If non-@code{nil}, this should be a function that accepts the same
1331 arguments as @code{read-file-name}. When @code{read-file-name} is
1332 called, it calls this function with the supplied arguments instead of
1333 doing its usual work.
1336 @defvar read-file-name-completion-ignore-case
1337 If this variable is non-@code{nil}, @code{read-file-name} ignores case
1338 when performing completion.
1341 @defun read-directory-name prompt &optional directory default existing initial
1342 This function is like @code{read-file-name} but allows only directory
1343 names as completion possibilities.
1345 If @var{default} is @code{nil} and @var{initial} is non-@code{nil},
1346 @code{read-directory-name} constructs a substitute default by
1347 combining @var{directory} (or the current buffer's default directory
1348 if @var{directory} is @code{nil}) and @var{initial}. If both
1349 @var{default} and @var{initial} are @code{nil}, this function uses
1350 @var{directory} as substitute default, or the current buffer's default
1351 directory if @var{directory} is @code{nil}.
1354 @defopt insert-default-directory
1355 This variable is used by @code{read-file-name}, and thus, indirectly,
1356 by most commands reading file names. (This includes all commands that
1357 use the code letters @samp{f} or @samp{F} in their interactive form.
1358 @xref{Interactive Codes,, Code Characters for interactive}.) Its
1359 value controls whether @code{read-file-name} starts by placing the
1360 name of the default directory in the minibuffer, plus the initial file
1361 name if any. If the value of this variable is @code{nil}, then
1362 @code{read-file-name} does not place any initial input in the
1363 minibuffer (unless you specify initial input with the @var{initial}
1364 argument). In that case, the default directory is still used for
1365 completion of relative file names, but is not displayed.
1367 If this variable is @code{nil} and the initial minibuffer contents are
1368 empty, the user may have to explicitly fetch the next history element
1369 to access a default value. If the variable is non-@code{nil}, the
1370 initial minibuffer contents are always non-empty and the user can
1371 always request a default value by immediately typing @key{RET} in an
1372 unedited minibuffer. (See above.)
1378 ;; @r{Here the minibuffer starts out with the default directory.}
1379 (let ((insert-default-directory t))
1380 (read-file-name "The file is "))
1384 ---------- Buffer: Minibuffer ----------
1385 The file is ~lewis/manual/@point{}
1386 ---------- Buffer: Minibuffer ----------
1390 ;; @r{Here the minibuffer is empty and only the prompt}
1391 ;; @r{appears on its line.}
1392 (let ((insert-default-directory nil))
1393 (read-file-name "The file is "))
1397 ---------- Buffer: Minibuffer ----------
1398 The file is @point{}
1399 ---------- Buffer: Minibuffer ----------
1404 @node Programmed Completion
1405 @subsection Programmed Completion
1406 @cindex programmed completion
1408 Sometimes it is not possible to create an alist or an obarray
1409 containing all the intended possible completions. In such a case, you
1410 can supply your own function to compute the completion of a given string.
1411 This is called @dfn{programmed completion}.
1413 To use this feature, pass a symbol with a function definition as the
1414 @var{collection} argument to @code{completing-read}. The function
1415 @code{completing-read} arranges to pass your completion function along
1416 to @code{try-completion} and @code{all-completions}, which will then let
1417 your function do all the work.
1419 The completion function should accept three arguments:
1423 The string to be completed.
1426 The predicate function to filter possible matches, or @code{nil} if
1427 none. Your function should call the predicate for each possible match,
1428 and ignore the possible match if the predicate returns @code{nil}.
1431 A flag specifying the type of operation.
1434 There are three flag values for three operations:
1438 @code{nil} specifies @code{try-completion}. The completion function
1439 should return the completion of the specified string, or @code{t} if the
1440 string is a unique and exact match already, or @code{nil} if the string
1441 matches no possibility.
1443 If the string is an exact match for one possibility, but also matches
1444 other longer possibilities, the function should return the string, not
1448 @code{t} specifies @code{all-completions}. The completion function
1449 should return a list of all possible completions of the specified
1453 @code{lambda} specifies @code{test-completion}. The completion
1454 function should return @code{t} if the specified string is an exact
1455 match for some possibility; @code{nil} otherwise.
1458 It would be consistent and clean for completion functions to allow
1459 lambda expressions (lists that are functions) as well as function
1460 symbols as @var{collection}, but this is impossible. Lists as
1461 completion tables already have other meanings, and it would be
1462 unreliable to treat one differently just because it is also a possible
1463 function. So you must arrange for any function you wish to use for
1464 completion to be encapsulated in a symbol.
1466 Emacs uses programmed completion when completing file names.
1467 @xref{File Name Completion}.
1469 @defmac dynamic-completion-table function
1470 This macro is a convenient way to write a function that can act as
1471 programmed completion function. The argument @var{function} should be
1472 a function that takes one argument, a string, and returns an alist of
1473 possible completions of it. You can think of
1474 @code{dynamic-completion-table} as a transducer between that interface
1475 and the interface for programmed completion functions.
1478 @node Yes-or-No Queries
1479 @section Yes-or-No Queries
1480 @cindex asking the user questions
1481 @cindex querying the user
1482 @cindex yes-or-no questions
1484 This section describes functions used to ask the user a yes-or-no
1485 question. The function @code{y-or-n-p} can be answered with a single
1486 character; it is useful for questions where an inadvertent wrong answer
1487 will not have serious consequences. @code{yes-or-no-p} is suitable for
1488 more momentous questions, since it requires three or four characters to
1491 If either of these functions is called in a command that was invoked
1492 using the mouse---more precisely, if @code{last-nonmenu-event}
1493 (@pxref{Command Loop Info}) is either @code{nil} or a list---then it
1494 uses a dialog box or pop-up menu to ask the question. Otherwise, it
1495 uses keyboard input. You can force use of the mouse or use of keyboard
1496 input by binding @code{last-nonmenu-event} to a suitable value around
1499 Strictly speaking, @code{yes-or-no-p} uses the minibuffer and
1500 @code{y-or-n-p} does not; but it seems best to describe them together.
1502 @defun y-or-n-p prompt
1503 This function asks the user a question, expecting input in the echo
1504 area. It returns @code{t} if the user types @kbd{y}, @code{nil} if the
1505 user types @kbd{n}. This function also accepts @key{SPC} to mean yes
1506 and @key{DEL} to mean no. It accepts @kbd{C-]} to mean ``quit'', like
1507 @kbd{C-g}, because the question might look like a minibuffer and for
1508 that reason the user might try to use @kbd{C-]} to get out. The answer
1509 is a single character, with no @key{RET} needed to terminate it. Upper
1510 and lower case are equivalent.
1512 ``Asking the question'' means printing @var{prompt} in the echo area,
1513 followed by the string @w{@samp{(y or n) }}. If the input is not one of
1514 the expected answers (@kbd{y}, @kbd{n}, @kbd{@key{SPC}},
1515 @kbd{@key{DEL}}, or something that quits), the function responds
1516 @samp{Please answer y or n.}, and repeats the request.
1518 This function does not actually use the minibuffer, since it does not
1519 allow editing of the answer. It actually uses the echo area (@pxref{The
1520 Echo Area}), which uses the same screen space as the minibuffer. The
1521 cursor moves to the echo area while the question is being asked.
1523 The answers and their meanings, even @samp{y} and @samp{n}, are not
1524 hardwired. The keymap @code{query-replace-map} specifies them.
1525 @xref{Search and Replace}.
1527 In the following example, the user first types @kbd{q}, which is
1528 invalid. At the next prompt the user types @kbd{y}.
1532 (y-or-n-p "Do you need a lift? ")
1534 ;; @r{After evaluation of the preceding expression,}
1535 ;; @r{the following prompt appears in the echo area:}
1539 ---------- Echo area ----------
1540 Do you need a lift? (y or n)
1541 ---------- Echo area ----------
1544 ;; @r{If the user then types @kbd{q}, the following appears:}
1547 ---------- Echo area ----------
1548 Please answer y or n. Do you need a lift? (y or n)
1549 ---------- Echo area ----------
1552 ;; @r{When the user types a valid answer,}
1553 ;; @r{it is displayed after the question:}
1556 ---------- Echo area ----------
1557 Do you need a lift? (y or n) y
1558 ---------- Echo area ----------
1563 We show successive lines of echo area messages, but only one actually
1564 appears on the screen at a time.
1567 @defun y-or-n-p-with-timeout prompt seconds default-value
1568 Like @code{y-or-n-p}, except that if the user fails to answer within
1569 @var{seconds} seconds, this function stops waiting and returns
1570 @var{default-value}. It works by setting up a timer; see @ref{Timers}.
1571 The argument @var{seconds} may be an integer or a floating point number.
1574 @defun yes-or-no-p prompt
1575 This function asks the user a question, expecting input in the
1576 minibuffer. It returns @code{t} if the user enters @samp{yes},
1577 @code{nil} if the user types @samp{no}. The user must type @key{RET} to
1578 finalize the response. Upper and lower case are equivalent.
1580 @code{yes-or-no-p} starts by displaying @var{prompt} in the echo area,
1581 followed by @w{@samp{(yes or no) }}. The user must type one of the
1582 expected responses; otherwise, the function responds @samp{Please answer
1583 yes or no.}, waits about two seconds and repeats the request.
1585 @code{yes-or-no-p} requires more work from the user than
1586 @code{y-or-n-p} and is appropriate for more crucial decisions.
1592 (yes-or-no-p "Do you really want to remove everything? ")
1594 ;; @r{After evaluation of the preceding expression,}
1595 ;; @r{the following prompt appears,}
1596 ;; @r{with an empty minibuffer:}
1600 ---------- Buffer: minibuffer ----------
1601 Do you really want to remove everything? (yes or no)
1602 ---------- Buffer: minibuffer ----------
1607 If the user first types @kbd{y @key{RET}}, which is invalid because this
1608 function demands the entire word @samp{yes}, it responds by displaying
1609 these prompts, with a brief pause between them:
1613 ---------- Buffer: minibuffer ----------
1614 Please answer yes or no.
1615 Do you really want to remove everything? (yes or no)
1616 ---------- Buffer: minibuffer ----------
1621 @node Multiple Queries
1622 @section Asking Multiple Y-or-N Questions
1624 When you have a series of similar questions to ask, such as ``Do you
1625 want to save this buffer'' for each buffer in turn, you should use
1626 @code{map-y-or-n-p} to ask the collection of questions, rather than
1627 asking each question individually. This gives the user certain
1628 convenient facilities such as the ability to answer the whole series at
1631 @defun map-y-or-n-p prompter actor list &optional help action-alist no-cursor-in-echo-area
1632 This function asks the user a series of questions, reading a
1633 single-character answer in the echo area for each one.
1635 The value of @var{list} specifies the objects to ask questions about.
1636 It should be either a list of objects or a generator function. If it is
1637 a function, it should expect no arguments, and should return either the
1638 next object to ask about, or @code{nil} meaning stop asking questions.
1640 The argument @var{prompter} specifies how to ask each question. If
1641 @var{prompter} is a string, the question text is computed like this:
1644 (format @var{prompter} @var{object})
1648 where @var{object} is the next object to ask about (as obtained from
1651 If not a string, @var{prompter} should be a function of one argument
1652 (the next object to ask about) and should return the question text. If
1653 the value is a string, that is the question to ask the user. The
1654 function can also return @code{t} meaning do act on this object (and
1655 don't ask the user), or @code{nil} meaning ignore this object (and don't
1658 The argument @var{actor} says how to act on the answers that the user
1659 gives. It should be a function of one argument, and it is called with
1660 each object that the user says yes for. Its argument is always an
1661 object obtained from @var{list}.
1663 If the argument @var{help} is given, it should be a list of this form:
1666 (@var{singular} @var{plural} @var{action})
1670 where @var{singular} is a string containing a singular noun that
1671 describes the objects conceptually being acted on, @var{plural} is the
1672 corresponding plural noun, and @var{action} is a transitive verb
1673 describing what @var{actor} does.
1675 If you don't specify @var{help}, the default is @code{("object"
1676 "objects" "act on")}.
1678 Each time a question is asked, the user may enter @kbd{y}, @kbd{Y}, or
1679 @key{SPC} to act on that object; @kbd{n}, @kbd{N}, or @key{DEL} to skip
1680 that object; @kbd{!} to act on all following objects; @key{ESC} or
1681 @kbd{q} to exit (skip all following objects); @kbd{.} (period) to act on
1682 the current object and then exit; or @kbd{C-h} to get help. These are
1683 the same answers that @code{query-replace} accepts. The keymap
1684 @code{query-replace-map} defines their meaning for @code{map-y-or-n-p}
1685 as well as for @code{query-replace}; see @ref{Search and Replace}.
1687 You can use @var{action-alist} to specify additional possible answers
1688 and what they mean. It is an alist of elements of the form
1689 @code{(@var{char} @var{function} @var{help})}, each of which defines one
1690 additional answer. In this element, @var{char} is a character (the
1691 answer); @var{function} is a function of one argument (an object from
1692 @var{list}); @var{help} is a string.
1694 When the user responds with @var{char}, @code{map-y-or-n-p} calls
1695 @var{function}. If it returns non-@code{nil}, the object is considered
1696 ``acted upon'', and @code{map-y-or-n-p} advances to the next object in
1697 @var{list}. If it returns @code{nil}, the prompt is repeated for the
1700 Normally, @code{map-y-or-n-p} binds @code{cursor-in-echo-area} while
1701 prompting. But if @var{no-cursor-in-echo-area} is non-@code{nil}, it
1704 If @code{map-y-or-n-p} is called in a command that was invoked using the
1705 mouse---more precisely, if @code{last-nonmenu-event} (@pxref{Command
1706 Loop Info}) is either @code{nil} or a list---then it uses a dialog box
1707 or pop-up menu to ask the question. In this case, it does not use
1708 keyboard input or the echo area. You can force use of the mouse or use
1709 of keyboard input by binding @code{last-nonmenu-event} to a suitable
1710 value around the call.
1712 The return value of @code{map-y-or-n-p} is the number of objects acted on.
1715 @node Reading a Password
1716 @section Reading a Password
1717 @cindex passwords, reading
1719 To read a password to pass to another program, you can use the
1720 function @code{read-passwd}.
1722 @defun read-passwd prompt &optional confirm default
1723 This function reads a password, prompting with @var{prompt}. It does
1724 not echo the password as the user types it; instead, it echoes @samp{.}
1725 for each character in the password.
1727 The optional argument @var{confirm}, if non-@code{nil}, says to read the
1728 password twice and insist it must be the same both times. If it isn't
1729 the same, the user has to type it over and over until the last two
1732 The optional argument @var{default} specifies the default password to
1733 return if the user enters empty input. If @var{default} is @code{nil},
1734 then @code{read-passwd} returns the null string in that case.
1737 @node Minibuffer Commands
1738 @section Minibuffer Commands
1740 This section describes some commands meant for use in the
1743 @deffn Command exit-minibuffer
1744 This command exits the active minibuffer. It is normally bound to
1745 keys in minibuffer local keymaps.
1748 @deffn Command self-insert-and-exit
1749 This command exits the active minibuffer after inserting the last
1750 character typed on the keyboard (found in @code{last-command-char};
1751 @pxref{Command Loop Info}).
1754 @deffn Command previous-history-element n
1755 This command replaces the minibuffer contents with the value of the
1756 @var{n}th previous (older) history element.
1759 @deffn Command next-history-element n
1760 This command replaces the minibuffer contents with the value of the
1761 @var{n}th more recent history element.
1764 @deffn Command previous-matching-history-element pattern n
1765 This command replaces the minibuffer contents with the value of the
1766 @var{n}th previous (older) history element that matches @var{pattern} (a
1767 regular expression).
1770 @deffn Command next-matching-history-element pattern n
1771 This command replaces the minibuffer contents with the value of the
1772 @var{n}th next (newer) history element that matches @var{pattern} (a
1773 regular expression).
1776 @node Minibuffer Windows
1777 @section Minibuffer Windows
1779 These functions access and select minibuffer windows
1780 and test whether they are active.
1782 @defun active-minibuffer-window
1783 This function returns the currently active minibuffer window, or
1784 @code{nil} if none is currently active.
1787 @defun minibuffer-window &optional frame
1788 @anchor{Definition of minibuffer-window}
1789 This function returns the minibuffer window used for frame @var{frame}.
1790 If @var{frame} is @code{nil}, that stands for the current frame. Note
1791 that the minibuffer window used by a frame need not be part of that
1792 frame---a frame that has no minibuffer of its own necessarily uses some
1793 other frame's minibuffer window.
1796 @defun set-minibuffer-window window
1797 This function specifies @var{window} as the minibuffer window to use.
1798 This affects where the minibuffer is displayed if you put text in it
1799 without invoking the usual minibuffer commands. It has no effect on
1800 the usual minibuffer input functions because they all start by
1801 choosing the minibuffer window according to the current frame.
1805 @defun window-minibuffer-p &optional window
1806 This function returns non-@code{nil} if @var{window} is a minibuffer
1808 @var{window} defaults to the selected window.
1811 It is not correct to determine whether a given window is a minibuffer by
1812 comparing it with the result of @code{(minibuffer-window)}, because
1813 there can be more than one minibuffer window if there is more than one
1816 @defun minibuffer-window-active-p window
1817 This function returns non-@code{nil} if @var{window}, assumed to be
1818 a minibuffer window, is currently active.
1821 @node Minibuffer Contents
1822 @section Minibuffer Contents
1824 These functions access the minibuffer prompt and contents.
1826 @defun minibuffer-prompt
1827 This function returns the prompt string of the currently active
1828 minibuffer. If no minibuffer is active, it returns @code{nil}.
1831 @defun minibuffer-prompt-end
1832 @tindex minibuffer-prompt-end
1833 This function returns the current
1834 position of the end of the minibuffer prompt, if a minibuffer is
1835 current. Otherwise, it returns the minimum valid buffer position.
1838 @defun minibuffer-prompt-width
1839 This function returns the current display-width of the minibuffer
1840 prompt, if a minibuffer is current. Otherwise, it returns zero.
1843 @defun minibuffer-contents
1844 @tindex minibuffer-contents
1845 This function returns the editable
1846 contents of the minibuffer (that is, everything except the prompt) as
1847 a string, if a minibuffer is current. Otherwise, it returns the
1848 entire contents of the current buffer.
1851 @defun minibuffer-contents-no-properties
1852 @tindex minibuffer-contents-no-properties
1853 This is like @code{minibuffer-contents}, except that it does not copy text
1854 properties, just the characters themselves. @xref{Text Properties}.
1857 @defun minibuffer-completion-contents
1858 @tindex minibuffer-completion-contents
1859 This is like @code{minibuffer-contents}, except that it returns only
1860 the contents before point. That is the part that completion commands
1861 operate on. @xref{Minibuffer Completion}.
1864 @defun delete-minibuffer-contents
1865 @tindex delete-minibuffer-contents
1866 This function erases the editable contents of the minibuffer (that is,
1867 everything except the prompt), if a minibuffer is current. Otherwise,
1868 it erases the entire current buffer.
1871 @node Recursive Mini
1872 @section Recursive Minibuffers
1874 These functions and variables deal with recursive minibuffers
1875 (@pxref{Recursive Editing}):
1877 @defun minibuffer-depth
1878 This function returns the current depth of activations of the
1879 minibuffer, a nonnegative integer. If no minibuffers are active, it
1883 @defopt enable-recursive-minibuffers
1884 If this variable is non-@code{nil}, you can invoke commands (such as
1885 @code{find-file}) that use minibuffers even while the minibuffer window
1886 is active. Such invocation produces a recursive editing level for a new
1887 minibuffer. The outer-level minibuffer is invisible while you are
1888 editing the inner one.
1890 If this variable is @code{nil}, you cannot invoke minibuffer
1891 commands when the minibuffer window is active, not even if you switch to
1892 another window to do it.
1896 If a command name has a property @code{enable-recursive-minibuffers}
1897 that is non-@code{nil}, then the command can use the minibuffer to read
1898 arguments even if it is invoked from the minibuffer. A command can
1899 also achieve this by binding @code{enable-recursive-minibuffers}
1900 to @code{t} in the interactive declaration (@pxref{Using Interactive}).
1901 The minibuffer command @code{next-matching-history-element} (normally
1902 @kbd{M-s} in the minibuffer) does the latter.
1904 @node Minibuffer Misc
1905 @section Minibuffer Miscellany
1907 @defun minibufferp &optional buffer-or-name
1908 This function returns non-@code{nil} if @var{buffer-or-name} is a
1909 minibuffer. If @var{buffer-or-name} is omitted, it tests the current
1913 @defvar minibuffer-setup-hook
1914 This is a normal hook that is run whenever the minibuffer is entered.
1918 @defvar minibuffer-exit-hook
1919 This is a normal hook that is run whenever the minibuffer is exited.
1923 @defvar minibuffer-help-form
1924 @anchor{Definition of minibuffer-help-form}
1925 The current value of this variable is used to rebind @code{help-form}
1926 locally inside the minibuffer (@pxref{Help Functions}).
1929 @defvar minibuffer-scroll-window
1930 @anchor{Definition of minibuffer-scroll-window}
1931 If the value of this variable is non-@code{nil}, it should be a window
1932 object. When the function @code{scroll-other-window} is called in the
1933 minibuffer, it scrolls this window.
1936 @defun minibuffer-selected-window
1937 This function returns the window which was selected when the
1938 minibuffer was entered. If selected window is not a minibuffer
1939 window, it returns @code{nil}.
1942 @defopt max-mini-window-height
1943 This variable specifies the maximum height for resizing minibuffer
1944 windows. If a float, it specifies a fraction of the height of the
1945 frame. If an integer, it specifies a number of lines.
1948 @defun minibuffer-message string
1949 This function displays @var{string} temporarily at the end of the
1950 minibuffer text, for two seconds, or until the next input event
1951 arrives, whichever comes first.
1955 arch-tag: bba7f945-9078-477f-a2ce-18818a6e1218