This section describes the higher-level convenience functions for reading certain sorts of names with completion.
In most cases, you should not call these functions in the middle of a
Lisp function. When possible, do all minibuffer input as part of
reading the arguments for a command, in the interactive
specification. See Defining Commands.
This function reads the name of a buffer and returns it as a string.
It prompts with prompt. The argument default is the
default name to use, the value to return if the user exits with an
empty minibuffer. If non-nil, it should be a string, a list of
strings, or a buffer. If it is a list, the default value is the first
element of this list. It is mentioned in the prompt, but is not
inserted in the minibuffer as initial input.
The argument prompt should be a string ending with a colon and a
space. If default is non-nil, the function inserts it in
prompt before the colon to follow the convention for reading from
the minibuffer with a default value (see Emacs Programming Tips).
The optional argument require-match has the same meaning as in
completing-read. See Completion and the Minibuffer.
The optional argument predicate, if non-nil, specifies a
function to filter the buffers that should be considered: the function
will be called with every potential candidate as its argument, and
should return nil to reject the candidate, non-nil to
accept it.
In the following example, the user enters ‘minibuffer.t’, and
then types RET. The argument require-match is t,
and the only buffer name starting with the given input is
‘minibuffer.texi’, so that name is the value.
(read-buffer "Buffer name: " "foo" t)
;; After evaluation of the preceding expression, ;; the following prompt appears, ;; with an empty minibuffer:
---------- Buffer: Minibuffer ---------- Buffer name (default foo): ∗ ---------- Buffer: Minibuffer ----------
;; The user types minibuffer.t RET.
⇒ "minibuffer.texi"
This variable, if non-nil, specifies a function for reading
buffer names. read-buffer calls this function instead of doing
its usual work, with the same arguments passed to read-buffer.
If this variable is non-nil, read-buffer ignores case
when performing completion while reading the buffer name.
This function reads the name of a command and returns it as a Lisp
symbol. The argument prompt is used as in
read-from-minibuffer. Recall that a command is anything for
which commandp returns t, and a command name is a symbol
for which commandp returns t. See Interactive Call.
The argument default specifies what to return if the user enters
null input. It can be a symbol, a string or a list of strings. If it
is a string, read-command interns it before returning it.
If it is a list, read-command interns the first element of this list.
If default is nil, that means no default has been
specified; then if the user enters null input, the return value is
(intern ""), that is, a symbol whose name is an empty string,
and whose printed representation is ## (see Symbol Type).
(read-command "Command name? ")
;; After evaluation of the preceding expression, ;; the following prompt appears with an empty minibuffer:
---------- Buffer: Minibuffer ---------- Command name? ---------- Buffer: Minibuffer ----------
If the user types forward-c RET, then this function returns
forward-char.
The read-command function is a simplified interface to
completing-read. It uses the variable obarray so as to
complete in the set of extant Lisp symbols, and it uses the
commandp predicate so as to accept only command names:
(read-command prompt)
≡
(intern (completing-read prompt obarray
'commandp t nil))
This function reads the name of a customizable variable and returns it
as a symbol. Its arguments have the same form as those of
read-command. It behaves just like read-command, except
that it uses the predicate custom-variable-p instead of
commandp.
This function reads a string that is a color specification, either the
color’s name or an RGB hex value such as #RRRGGGBBB. It
prompts with prompt (default: "Color (name or #RGB triplet):")
and provides completion for color names, but not for hex RGB values.
In addition to names of standard colors, completion candidates include
the foreground and background colors at point.
Valid RGB values are described in Color Names.
The function’s return value is the string typed by the user in the
minibuffer. However, when called interactively or if the optional
argument convert is non-nil, it converts any input color
name into the corresponding RGB value string and instead returns that.
This function requires a valid color specification to be input.
Empty color names are allowed when allow-empty is
non-nil and the user enters null input.
Interactively, or when display is non-nil, the return
value is also displayed in the echo area.
See also the functions read-coding-system and
read-non-nil-coding-system, in User-Chosen Coding Systems,
and read-input-method-name, in Input Methods.