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### 19.2 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`.

  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`. 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.

  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)
          value))

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:

  - âˆ’ `regexp-history-last`, which means to use the first element of the appropriate minibuffer history list (see below).
  - âˆ’ 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:

  - âˆ’ The word or symbol at point.
  - âˆ’ The last regexp used in an incremental search.
  - âˆ’ The last string used in an incremental search.
  - âˆ’ 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`.

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:

  - âˆ’ The symbol `regexp-history-last`.
  - âˆ’ 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, discard text properties unconditionally, regardless of the value of this variable.

Variable: minibuffer-local-map

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

  `C-j`

    `exit-minibuffer`

  `RET`

    `exit-minibuffer`

  `C-g`

    `abort-recursive-edit`

  `M-n`
  `DOWN`

    `next-history-element`

  `M-p`
  `UP`

    `previous-history-element`

  `M-s`

    `next-matching-history-element`

  `M-r`

    `previous-matching-history-element`

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`:

  `SPC`

    `exit-minibuffer`

  `TAB`

    `exit-minibuffer`

  `?`

    `self-insert-and-exit`

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