21.2 Reading Text Strings with the Minibuffer

The most basic primitive for minibuffer input is read-from-minibuffer, which can be used to read either a string or a Lisp object in textual form. The function read-regexp is used for reading regular expressions (see Regular Expressions), which are a special kind of string. There are also specialized functions for reading commands, variables, file names, etc. (see Completion).

In most cases, you should not call minibuffer input functions in the middle of a Lisp function. Instead, do all minibuffer input as part of reading the arguments for a command, in the interactive specification. See Defining Commands.

Function: read-from-minibuffer prompt &optional initial keymap read history default inherit-input-method

This function is the most general way to get input from the minibuffer. By default, it accepts arbitrary text and returns it as a string; however, if read is non-nil, then it uses read to convert the text into a Lisp object (see Input Functions).

The first thing this function does is to activate a minibuffer and display it with prompt (which must be a string) as the prompt. Then the user can edit text in the minibuffer.

When the user types a command to exit the minibuffer, read-from-minibuffer constructs the return value from the text in the minibuffer. Normally it returns a string containing that text. However, if read is non-nil, read-from-minibuffer reads the text and returns the resulting Lisp object, unevaluated. (See Input Functions, for information about reading.)

The argument default specifies default values to make available through the history commands. It should be a string, a list of strings, or nil. The string or strings become the minibuffer’s “future history”, available to the user with M-n. In addition, if the call provides completion (e.g., via the keymap argument), the completion candidates are added to the “future history” when the values in default are exhausted by M-n; see minibuffer-default-add-function.

If read is non-nil, then default is also used as the input to read, if the user enters empty input. If default is a list of strings, the first string is used as the input. If default is nil, empty input results in an end-of-file error. However, in the usual case (where read is nil), read-from-minibuffer ignores default when the user enters empty input and returns an empty string, "". In this respect, it differs from all the other minibuffer input functions in this chapter.

If keymap is non-nil, that keymap is the local keymap to use in the minibuffer. If keymap is omitted or nil, the value of minibuffer-local-map is used as the keymap. Specifying a keymap is the most important way to customize the minibuffer for various applications such as completion.

The argument history specifies a history list variable to use for saving the input and for history commands used in the minibuffer. It defaults to minibuffer-history. If history is the symbol t, history is not recorded. You can optionally specify a starting position in the history list as well. See Minibuffer History.

If the variable minibuffer-allow-text-properties is non-nil, then the string that is returned includes whatever text properties were present in the minibuffer. Otherwise all the text properties are stripped when the value is returned.

The text properties in minibuffer-prompt-properties are applied to the prompt. By default, this property list defines a face to use for the prompt. This face, if present, is applied to the end of the face list and merged before display.

If the user wants to completely control the look of the prompt, the most convenient way to do that is to specify the default face at the end of all face lists. For instance:

  (propertize "Bold" 'face '(bold default))
  (propertize " and normal: " 'face '(default))))

If the argument inherit-input-method is non-nil, then the minibuffer inherits the current input method (see Input Methods) and the setting of enable-multibyte-characters (see Text Representations) from whichever buffer was current before entering the minibuffer.

Use of initial is mostly deprecated; we recommend using a non-nil value only in conjunction with specifying a cons cell for history. See Initial Input.

Function: read-string prompt &optional initial history default inherit-input-method

This function reads a string from the minibuffer and returns it. The arguments prompt, initial, history and inherit-input-method are used as in read-from-minibuffer. The keymap used is minibuffer-local-map.

The optional argument default is used as in read-from-minibuffer, except that, if non-nil, it also specifies a default value to return if the user enters null input. As in read-from-minibuffer it should be a string, a list of strings, or nil, which is equivalent to an empty string. When default is a string, that string is the default value. When it is a list of strings, the first string is the default value. (All these strings are available to the user in the “future minibuffer history”.)

This function works by calling the read-from-minibuffer function:

(read-string prompt initial history default inherit)
(let ((value
       (read-from-minibuffer prompt initial nil nil
                             history default inherit)))
  (if (and (equal value "") default)
      (if (consp default) (car default) default)

If you have a long string (for instance, one that is several lines long) that you wish to edit, using read-string may not be ideal. In that case, popping to a new, normal buffer where the user can edit the string may be more convenient, and you can use the read-string-from-buffer function to do that.

Function: read-regexp prompt &optional defaults history

This function reads a regular expression as a string from the minibuffer and returns it. If the minibuffer prompt string prompt does not end in ‘:’ (followed by optional whitespace), the function adds ‘: ’ to the end, preceded by the default return value (see below), if that is non-empty.

The optional argument defaults controls the default value to return if the user enters null input, and should be one of: a string; nil, which is equivalent to an empty string; a list of strings; or a symbol.

If defaults is a symbol, read-regexp consults the value of the variable read-regexp-defaults-function (see below), and if that is non-nil uses it in preference to defaults. The value in this case should be either:

  • regexp-history-last, which means to use the first element of the appropriate minibuffer history list (see below).
  • A function of no arguments, whose return value (which should be nil, a string, or a list of strings) becomes the value of defaults.

read-regexp now ensures that the result of processing defaults is a list (i.e., if the value is nil or a string, it converts it to a list of one element). To this list, read-regexp then appends a few potentially useful candidates for input. These are:

  • The word or symbol at point.
  • The last regexp used in an incremental search.
  • The last string used in an incremental search.
  • The last string or pattern used in query-replace commands.

The function now has a list of regular expressions that it passes to read-from-minibuffer to obtain the user’s input. The first element of the list is the default result in case of empty input. All elements of the list are available to the user as the “future minibuffer history” list (see future list in The GNU Emacs Manual).

The optional argument history, if non-nil, is a symbol specifying a minibuffer history list to use (see Minibuffer History). If it is omitted or nil, the history list defaults to regexp-history.

The user can use the M-s c command to indicate whether case folding should be on or off. If the user has used this command, the returned string will have the text property case-fold set to either fold or inhibit-fold. It is up to the caller of read-regexp to actually use this value, and the convenience function read-regexp-case-fold-search is provided for that. A typical usage pattern here might look like:

(let* ((regexp (read-regexp "Search for: "))
       (case-fold-search (read-regexp-case-fold-search regexp)))
  (re-search-forward regexp))
User Option: read-regexp-defaults-function

The function read-regexp may use the value of this variable to determine its list of default regular expressions. If non-nil, the value of this variable should be either:

  • The symbol regexp-history-last.
  • A function of no arguments that returns either nil, a string, or a list of strings.

See read-regexp above for details of how these values are used.

Variable: minibuffer-allow-text-properties

If this variable is nil, then read-from-minibuffer and read-string strip all text properties from the minibuffer input before returning it. However, read-no-blanks-input (see below), as well as read-minibuffer and related functions (see Reading Lisp Objects With the Minibuffer), and all functions that do minibuffer input with completion, remove the face property unconditionally, regardless of the value of this variable.

If this variable is non-nil, most text properties on strings from the completion table are preserved—but only on the part of the strings that were completed.

(let ((minibuffer-allow-text-properties t))
  (completing-read "String: " (list (propertize "foobar" 'data 'zot))))
=> #("foobar" 3 6 (data zot))

In this example, the user typed ‘foo’ and then hit the TAB key, so the text properties are only preserved on the last three characters.

Variable: minibuffer-local-map

This is the default local keymap for reading from the minibuffer. By default, it makes the following bindings:

















The variable minibuffer-mode-map is an alias for this variable.

Function: read-no-blanks-input prompt &optional initial inherit-input-method

This function reads a string from the minibuffer, but does not allow whitespace characters as part of the input: instead, those characters terminate the input. The arguments prompt, initial, and inherit-input-method are used as in read-from-minibuffer.

This is a simplified interface to the read-from-minibuffer function, and passes the value of the minibuffer-local-ns-map keymap as the keymap argument for that function. Since the keymap minibuffer-local-ns-map does not rebind C-q, it is possible to put a space into the string, by quoting it.

This function discards text properties, regardless of the value of minibuffer-allow-text-properties.

(read-no-blanks-input prompt initial)
(let (minibuffer-allow-text-properties)
  (read-from-minibuffer prompt initial minibuffer-local-ns-map))
Variable: minibuffer-local-ns-map

This built-in variable is the keymap used as the minibuffer local keymap in the function read-no-blanks-input. By default, it makes the following bindings, in addition to those of minibuffer-local-map:







Function: format-prompt prompt default &rest format-args

Format prompt with default value default according to the minibuffer-default-prompt-format variable.

minibuffer-default-prompt-format is a format string (defaulting to ‘" (default %s)"’ that says how the “default” bit in prompts like ‘"Local filename (default somefile): "’ are to be formatted.

To allow the users to customize how this is displayed, code that prompts the user for a value (and has a default) should look something along the lines of this code snippet:

 (format-prompt "Local filename" file)
 nil file)

If format-args is nil, prompt is used as a literal string. If format-args is non-nil, prompt is used as a format control string, and prompt and format-args are passed to format (see Formatting Strings).

minibuffer-default-prompt-format can be ‘""’, in which case no default values are displayed.

If default is nil, there is no default value, and therefore no “default value” string is included in the result value. If default is a non-nil list, the first element of the list is used in the prompt.

Both prompt and minibuffer-default-prompt-format are run through substitute-command-keys (see Substituting Key Bindings in Documentation).

Variable: read-minibuffer-restore-windows

If this option is non-nil (the default), getting input from the minibuffer will restore, on exit, the window configurations of the frame where the minibuffer was entered from and, if it is different, the frame that owns the minibuffer window. This means that if, for example, a user splits a window while getting input from the minibuffer on the same frame, that split will be undone when exiting the minibuffer.

If this option is nil, no such restorations are done. Hence, the window split mentioned above will persist after exiting the minibuffer.