The minibuffer is an Emacs buffer, albeit a peculiar one, and the usual Emacs commands are available for editing the argument text. (The prompt, however, is read-only, and cannot be changed.)
Since <RET> in the minibuffer submits the argument, you can't
use it to insert a newline. You can do that with C-q C-j, which
inserts a C-j control character, which is formally equivalent to
a newline character (see Inserting Text). Alternatively, you can
use the C-o (
open-line) command (see Blank Lines).
Inside a minibuffer, the keys <TAB>, <SPC>, and ? are often bound to completion commands, which allow you to easily fill in the desired text without typing all of it. See Completion. As with <RET>, you can use C-q to insert a <TAB>, <SPC>, or ‘?’ character.
For convenience, C-a (
move-beginning-of-line) in a
minibuffer moves point to the beginning of the argument text, not the
beginning of the prompt. For example, this allows you to erase the
entire argument with C-a C-k.
When the minibuffer is active, the echo area is treated much like an ordinary Emacs window. For instance, you can switch to another window (with C-x o), edit text there, then return to the minibuffer window to finish the argument. You can even kill text in another window, return to the minibuffer window, and yank the text into the argument. There are some restrictions on the minibuffer window, however: for instance, you cannot split it. See Windows.
Normally, the minibuffer window occupies a single screen line.
However, if you add two or more lines' worth of text into the
minibuffer, it expands automatically to accommodate the text. The
resize-mini-windows controls the resizing of the
minibuffer. The default value is
grow-only, which means the
behavior we have just described. If the value is
minibuffer window will also shrink automatically if you remove some
lines of text from the minibuffer, down to a minimum of one screen
line. If the value is
nil, the minibuffer window never changes
size automatically, but you can use the usual window-resizing commands
on it (see Windows).
max-mini-window-height controls the maximum
height for resizing the minibuffer window. A floating-point number
specifies a fraction of the frame's height; an integer specifies the
maximum number of lines;
nil means do not resize the minibuffer
window automatically. The default value is 0.25.
The C-M-v command in the minibuffer scrolls the help text from commands that display help text of any sort in another window. You can also scroll the help text with M-<prior> and M-<next> (or, equivalently, M-<PageUp> and M-<PageDown>). This is especially useful with long lists of possible completions. See Other Window.
Emacs normally disallows most commands that use the minibuffer while
the minibuffer is active. To allow such commands in the minibuffer,
set the variable
When not active, the minibuffer is in
and clicking Mouse-1 there shows the *Messages* buffer.
If you use a dedicated frame for minibuffers, Emacs also recognizes
certain keys there, for example n to make a new frame.