20.1 Introduction to Minibuffers

In most ways, a minibuffer is a normal Emacs buffer. Most operations within a buffer, such as editing commands, work normally in a minibuffer. However, many operations for managing buffers do not apply to minibuffers. The name of a minibuffer always has the form ` *Minibuf-number', and it cannot be changed. Minibuffers are displayed only in special windows used only for minibuffers; these windows always appear at the bottom of a frame. (Sometimes frames have no minibuffer window, and sometimes a special kind of frame contains nothing but a minibuffer window; see 29.8 Minibuffers and Frames.)

The text in the minibuffer always starts with the prompt string, the text that was specified by the program that is using the minibuffer to tell the user what sort of input to type. This text is marked read-only so you won't accidentally delete or change it. It is also marked as a field (see section 32.19.10 Defining and Using Fields), so that certain motion functions, including beginning-of-line, forward-word, forward-sentence, and forward-paragraph, stop at the boundary between the prompt and the actual text. (In older Emacs versions, the prompt was displayed using a special mechanism and was not part of the buffer contents.)

The minibuffer's window is normally a single line; it grows automatically if necessary if the contents require more space. You can explicitly resize it temporarily with the window sizing commands; it reverts to its normal size when the minibuffer is exited. You can resize it permanently by using the window sizing commands in the frame's other window, when the minibuffer is not active. If the frame contains just a minibuffer, you can change the minibuffer's size by changing the frame's size.

If a command uses a minibuffer while there is an active minibuffer, this is called a recursive minibuffer. The first minibuffer is named ` *Minibuf-0*'. Recursive minibuffers are named by incrementing the number at the end of the name. (The names begin with a space so that they won't show up in normal buffer lists.) Of several recursive minibuffers, the innermost (or most recently entered) is the active minibuffer. We usually call this "the" minibuffer. You can permit or forbid recursive minibuffers by setting the variable enable-recursive-minibuffers or by putting properties of that name on command symbols (see section 20.9 Minibuffer Miscellany).

Like other buffers, a minibuffer may use any of several local keymaps (see section 22. Keymaps); these contain various exit commands and in some cases completion commands (see section 20.5 Completion).

• minibuffer-local-map is for ordinary input (no completion).

• minibuffer-local-ns-map is similar, except that SPC exits just like RET. This is used mainly for Mocklisp compatibility.

• minibuffer-local-completion-map is for permissive completion.

• minibuffer-local-must-match-map is for strict completion and for cautious completion.

When Emacs is running in batch mode, any request to read from the minibuffer actually reads a line from the standard input descriptor that was supplied when Emacs was started.