(Minibuffer File): Add xref to File Names.

[gnu-emacs] / doc / emacs / mini.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001,
@c   2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Minibuffer, M-x, Basic, Top
@chapter The Minibuffer
@cindex minibuffer

  The @dfn{minibuffer} is where Emacs commands read complicated
arguments, such as file names, buffer names, Emacs command names, or
Lisp expressions.  We call it the ``minibuffer'' because it's a
special-purpose buffer with a small amount of screen space.  You can
use the usual Emacs editing commands in the minibuffer to edit the
argument text.

@cindex prompt
  When the minibuffer is in use, it appears in the echo area, with a
cursor.  The minibuffer display starts with a @dfn{prompt} in a
distinct color, usually ending with a colon.  The prompt states what
kind of input is expected, and how it will be used.

  The simplest way to enter a minibuffer argument is to type the text,
then @key{RET} to submit the argument and exit the minibuffer.  You
can cancel the minibuffer, and the command that wants the argument, by
typing @kbd{C-g}.

@cindex default argument
  Sometimes, a @dfn{default argument} appears in the prompt, inside
parentheses before the colon.  The default will be used as the
argument value if you just type @key{RET}.  For example, commands that
read buffer names usually show a buffer name as the default; you can
type @key{RET} to operate on that default buffer.

  Since the minibuffer appears in the echo area, it can conflict with
other uses of the echo area.  If an error occurs while the minibuffer
is active, the error message hides the minibuffer for a few seconds,
or until you type something; then the minibuffer comes back.  If a
command such as @kbd{C-x =} needs to display a message in the echo
area, the message hides the minibuffer for a few seconds, or until you
type something; then the minibuffer comes back.  While the minibuffer
is in use, keystrokes do not echo.

@menu
* Minibuffer File::       Entering file names with the minibuffer.
* Minibuffer Edit::       How to edit in the minibuffer.
* Completion::            An abbreviation facility for minibuffer input.
* Minibuffer History::    Reusing recent minibuffer arguments.
* Repetition::            Re-executing commands that used the minibuffer.
@end menu

@node Minibuffer File
@section Minibuffers for File Names

  Commands such as @kbd{C-x C-f} (@code{find-file}) use the minibuffer
to read a file name argument (@pxref{Basic Files}).  When the
minibuffer is used to read a file name, it typically starts out with
some initial text ending in a slash.  This is the @dfn{default
directory}.  For example, it may start out like this:

@example
Find File: /u2/emacs/src/
@end example

@noindent
Here, @samp{Find File:@: } is the prompt and @samp{/u2/emacs/src/} is
the default directory.  If you now type @kbd{buffer.c} as input, that
specifies the file @file{/u2/emacs/src/buffer.c}.  @xref{File Names},
for information about the default directory.

  You can specify the parent directory by adding @file{..}: for
example, @file{/u2/emacs/src/../lisp/simple.el} is equivalent to
@file{/u2/emacs/lisp/simple.el}.  Alternatively, you can use
@kbd{M-@key{DEL}} to kill directory names backwards (@pxref{Words}).

  To specify a file in a completely different directory, you can kill
the entire default with @kbd{C-a C-k} (@pxref{Minibuffer Edit}).
Alternatively, you can ignore the default, and enter an absolute file
name starting with a slash or a tilde after the default directory.
For example, you can specify @file{/etc/termcap} as follows:

@example
Find File: /u2/emacs/src//etc/termcap
@end example

@noindent
@cindex // in file name
@cindex double slash in file name
@cindex slashes repeated in file name
@findex file-name-shadow-mode
Emacs interprets a double slash as ``ignore everything before the
second slash in the pair.''  In the example above,
@samp{/u2/emacs/src/} is ignored, so the argument you supplied is
@file{/etc/termcap}.  The ignored part of the file name is dimmed if
the terminal allows it (to disable this dimming, turn off File Name
Shadow mode with the command @kbd{M-x file-name-shadow-mode}.)

@cindex home directory shorthand
  Emacs interprets @samp{~/} as your home directory.  Thus,
@samp{~/foo/bar.txt} specifies a file named @samp{bar.txt}, inside a
directory named @samp{foo}, which is in turn located in your home
directory.  In addition, @file{~@var{user-id}/} means the home
directory of a user whose login name is @code{user-id}.  Any leading
directory name in front of the @samp{~} is ignored: thus,
@samp{/u2/emacs/~/foo/bar.txt} is equivalent to @samp{~/foo/bar.txt}.

  On MS-Windows and MS-DOS systems, where a user doesn't have a home
directory, Emacs replaces @file{~/} with the value of the environment
variable @code{HOME}; see @ref{General Variables}.  On these systems,
the @file{~@var{user-id}/} construct is supported only for the current
user, i.e., only if @var{user-id} is the current user's login name.

@vindex insert-default-directory
  To prevent Emacs from inserting the default directory when reading
file names, change the variable @code{insert-default-directory} to
@code{nil}.  In that case, the minibuffer starts out empty.
Nonetheless, relative file name arguments are still interpreted based
on the same default directory.

@node Minibuffer Edit
@section Editing in the Minibuffer

  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 @dfn{read-only}, and cannot be changed.)

  Since @key{RET} in the minibuffer is defined to exit the minibuffer,
you can't use it to insert a newline in the minibuffer.  To do that,
type @kbd{C-o} or @kbd{C-q C-j}.  (The newline character is really the
@acronym{ASCII} character control-J.)

  Inside a minibuffer, the keys @kbd{@key{TAB}}, @kbd{@key{SPC}}, and
@kbd{@key{?}} are often bound to commands that perform
@dfn{completion}.  @xref{Completion}.  You can use @kbd{C-q}
(@code{quoted-insert}) to insert a @key{TAB}, @key{SPC}, or @key{?}
character.  For example, @kbd{C-q @key{TAB}} inserts a @key{TAB}
character.  @xref{Inserting Text}.

  For convenience, @kbd{C-a} (@code{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 @kbd{C-a C-k}.

@cindex height of minibuffer
@cindex size of minibuffer
@cindex growing minibuffer
@cindex resizing minibuffer
  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 @kbd{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.  @xref{Windows}.

@vindex resize-mini-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 accomodate the text.  The
variable @code{resize-mini-windows} controls the resizing of the
minibuffer.  The default value is @code{grow-only}, which means the
behavior we have just described.  If the value is @code{t}, the
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 @code{nil}, the minibuffer window never changes
size automatically, but you can use the usual window-resizing commands
on it (@pxref{Windows}).

@vindex max-mini-window-height
  The variable @code{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; @code{nil} means do not resize the minibuffer
window automatically.  The default value is 0.25.

  The @kbd{C-M-v} command in the minibuffer scrolls the help text from
commands that display help text of any sort in another window.
@kbd{M-@key{PAGEUP}} and @kbd{M-@key{PAGEDOWN}} also operate on that
help text.  This is especially useful with long lists of possible
completions.  @xref{Other Window}.

@vindex enable-recursive-minibuffers
  Emacs normally disallows most commands that use the minibuffer while
the minibuffer is active.  To allow such commands in the minibuffer,
set the variable @code{enable-recursive-minibuffers} to @code{t}.

@node Completion
@section Completion
@c This node is referenced in the tutorial.  When renaming or deleting
@c it, the tutorial needs to be adjusted.
@cindex completion

  Sometimes, you can use a feature called @dfn{completion} to help you
enter arguments.  This means that after you type part of the argument,
Emacs can fill in the rest, or some of it, based on what you have
typed so far.

  When completion is available, certain keys (usually @key{TAB},
@key{RET}, and @key{SPC}) are rebound to complete the text in the
minibuffer into a longer string chosen from a set of @dfn{completion
alternatives}.  The set of completion alternatives depends on the
command that requested the argument, and on what you have typed so
far.  In addition, you can usually type @kbd{?} to display a list of
possible completions.

  For example, @kbd{M-x} uses the minibuffer to read the name of a
command, so completion works by matching the minibuffer text against
the names of existing Emacs commands.  So, to run the command
@code{insert-buffer}, you can type @kbd{M-x ins @key{SPC} b @key{RET}}
instead of the full @kbd{M-x insert-buffer @key{RET}}.

  Case is significant in completion when it is significant in the
argument you are entering, such as command names.  Thus,
@samp{insert-buffer} is not a valid completion for @samp{IN}.
Completion ignores case distinctions for certain arguments in which
case does not matter.

@menu
* Example: Completion Example.    Examples of using completion.
* Commands: Completion Commands.  A list of completion commands.
* Strict Completion::             Different types of completion.
* Options: Completion Options.    Options for completion.
@end menu

@node Completion Example
@subsection Completion Example

@kindex TAB @r{(completion)}
  A concrete example may help here.  If you type @kbd{M-x a u
@key{TAB}}, the @key{TAB} looks for alternatives (in this case,
command names) that start with @samp{au}.  There are several,
including @code{auto-fill-mode} and @code{autoconf-mode}, but they all
begin with @code{auto}, so the @samp{au} in the minibuffer completes
to @samp{auto}.

  If you type @key{TAB} again immediately, it cannot determine the
next character; it could be @samp{-}, @samp{a}, or @samp{c}.  So it
does not add any characters; instead, @key{TAB} displays a list of all
possible completions in another window.

  Next, type @kbd{- f}.  The minibuffer now contains @samp{auto-f},
and the only command name that starts with this is
@code{auto-fill-mode}.  If you now type @key{TAB}, completion fills in
the rest of the argument @samp{auto-fill-mode} into the minibuffer.
You have been able to enter @samp{auto-fill-mode} by typing just
@kbd{a u @key{TAB} - f @key{TAB}}.

@node Completion Commands
@subsection Completion Commands

  Here is a list of the completion commands defined in the minibuffer
when completion is allowed.

@table @kbd
@item @key{TAB}
@findex minibuffer-complete
Complete the text before point in the minibuffer as much as possible;
if unable to complete, display a list of possible completions
(@code{minibuffer-complete}).
@item @key{SPC}
Complete up to one word from the minibuffer text before point
(@code{minibuffer-complete-word}).  @key{SPC} for completion is not
available when entering a file name, since file names often include
spaces.
@item @key{RET}
Submit the text in the minibuffer as the argument, possibly completing
first as described in the next
@iftex
subsection (@code{minibuffer-complete-and-exit}).
@end iftex
@ifnottex
node (@code{minibuffer-complete-and-exit}).  @xref{Strict Completion}.
@end ifnottex
@item ?
Display a list of possible completions of the text before point
(@code{minibuffer-completion-help}).
@end table

@kindex SPC
@findex minibuffer-complete-word
  @key{SPC} (@code{minibuffer-complete-word}) completes like
@key{TAB}, but only up to the next hyphen or space.  If you have
@samp{auto-f} in the minibuffer and type @key{SPC}, it finds that the
completion is @samp{auto-fill-mode}, but it only inserts @samp{ill-},
giving @samp{auto-fill-}.  Another @key{SPC} at this point completes
all the way to @samp{auto-fill-mode}.

  When you display a list of possible completions, you can choose
one from it:

@table @kbd
@findex mouse-choose-completion
@item Mouse-1
@itemx Mouse-2
Clicking mouse button 1 or 2 on a completion possibility chooses that
completion (@code{mouse-choose-completion}).

@findex switch-to-completions
@item M-v
@itemx @key{PageUp}
@itemx @key{PRIOR}
Typing @kbd{M-v}, while in the minibuffer, selects the window showing
the completion list buffer (@code{switch-to-completions}).  This paves
the way for using the commands below.  Typing @key{PageUp} or
@key{PRIOR} does the same, as does selecting that window in other
ways.

@findex choose-completion
@item @key{RET}
Typing @key{RET}, while in the completion list buffer, chooses the
completion that point is in or next to (@code{choose-completion}).  To
use this command, you must first switch to the completion list window.

@findex next-completion
@item @key{Right}
Typing the right-arrow key @key{Right}, while in the completion list
buffer, moves point to the following completion possibility
(@code{next-completion}).

@findex previous-completion
@item @key{Left}
Typing the left-arrow key @key{Left}, while in the completion list
buffer, moves point to the previous completion possibility
(@code{previous-completion}).
@end table

@node Strict Completion
@subsection Strict Completion

  There are three different ways that @key{RET} can do completion,
depending on how the argument will be used.

@itemize @bullet
@item
@dfn{Strict} completion accepts only known completion candidates.  For
example, when @kbd{C-x k} reads the name of a buffer to kill, only the
name of an existing buffer makes sense.  In strict completion,
@key{RET} refuses to exit if the text in the minibuffer does not
complete to an exact match.

@item
@dfn{Cautious} completion is similar to strict completion, except that
@key{RET} exits only if the text is an already exact match.
Otherwise, @key{RET} does not exit, but it does complete the text.  If
that completes to an exact match, a second @key{RET} will exit.

Cautious completion is used for reading file names for files that must
already exist, for example.

@item
@dfn{Permissive} completion allows any input; the completion
candidates are just suggestions.  For example, when @kbd{C-x C-f}
reads the name of a file to visit, any file name is allowed, including
nonexistent file (in case you want to create a file).  In permissive
completion, @key{RET} does not complete, it just submits the argument
as you have entered it.
@end itemize

  The completion commands display a list of all possible completions
whenever they can't determine even one more character by completion.
Also, typing @kbd{?} explicitly requests such a list.  You can scroll
the list with @kbd{C-M-v} (@pxref{Other Window}).

@node Completion Options
@subsection Completion Options

@vindex completion-auto-help
  If @code{completion-auto-help} is set to @code{nil}, the completion
commands never display the completion list buffer; you must type
@kbd{?}  to display the list.  If the value is @code{lazy}, Emacs only
shows the completion list buffer on the second attempt to complete.
In other words, if there is nothing to complete, the first @key{TAB}
echoes @samp{Next char not unique}; the second @key{TAB} does the
completion list buffer buffer.

@vindex completion-ignored-extensions
@cindex ignored file names, in completion
  When completing file names, certain file names are usually ignored.
The variable @code{completion-ignored-extensions} contains a list of
strings; a file name ending in any of those strings is ignored as a
completion candidate.  The standard value of this variable has several
elements including @code{".o"}, @code{".elc"}, and @code{"~"}.  For
example, if a directory contains @samp{foo.c} and @samp{foo.elc},
@samp{foo} completes to @samp{foo.c}.  However, if @emph{all} possible
completions end in ``ignored'' strings, they are not ignored: in the
previous example, @samp{foo.e} completes to @samp{foo.elc}.
Displaying a list of possible completions disregards
@code{completion-ignored-extensions}; it shows them all.

  If an element of @code{completion-ignored-extensions} ends in a
slash (@file{/}), it's a subdirectory name; that directory and its
contents are ignored.  Elements of
@code{completion-ignored-extensions} that do not end in a slash are
ordinary file names.

@cindex Partial Completion mode
@vindex partial-completion-mode
@findex partial-completion-mode
  Partial Completion mode implements a more powerful kind of
completion that can complete multiple words in parallel.  For example,
it can complete the command name abbreviation @code{p-b} into
@code{print-buffer} if no other command starts with two words whose
initials are @samp{p} and @samp{b}.

  To enable this mode, use @kbd{M-x partial-completion-mode} or
customize the variable @code{partial-completion-mode}.  This mode
binds special partial completion commands to @key{TAB}, @key{SPC},
@key{RET}, and @kbd{?} in the minibuffer.  The usual completion
commands are available on @kbd{M-@key{TAB}} (or @kbd{C-M-i}),
@kbd{M-@key{SPC}}, @kbd{M-@key{RET}} and @kbd{M-?}.

  Partial completion of directories in file names uses @samp{*} to
indicate the places for completion; thus, @file{/u*/b*/f*} might
complete to @file{/usr/bin/foo}.  For remote files, partial completion
enables completion of methods, user names and host names.
@xref{Remote Files}.

@vindex PC-include-file-path
@vindex PC-disable-includes
  Partial Completion mode also extends @code{find-file} so that
@samp{<@var{include}>} looks for the file named @var{include} in the
directories in the path @code{PC-include-file-path}.  If you set
@code{PC-disable-includes} to non-@code{nil}, this feature is
disabled.

@cindex Icomplete mode
@findex icomplete-mode
  Icomplete mode presents a constantly-updated display that tells you
what completions are available for the text you've entered so far.  The
command to enable or disable this minor mode is @kbd{M-x
icomplete-mode}.

@node Minibuffer History
@section Minibuffer History
@cindex minibuffer history
@cindex history of minibuffer input

  Every argument that you enter with the minibuffer is saved in a
@dfn{minibuffer history list} so you can easily use it again later.
You can use the following arguments to quickly fetch an earlier
argument into the minibuffer:

@table @kbd
@item M-p
@itemx @key{Up}
Move to the previous item in the minibuffer history, an earlier
argument (@code{previous-history-element}).
@item M-n
@itemx @key{Down}
Move to the next item in the minibuffer history
(@code{next-history-element}).
@item M-r @var{regexp} @key{RET}
Move to an earlier item in the minibuffer history that 
matches @var{regexp} (@code{previous-matching-history-element}).
@item M-s @var{regexp} @key{RET}
Move to a later item in the minibuffer history that matches
@var{regexp} (@code{next-matching-history-element}).
@end table

@kindex M-p @r{(minibuffer history)}
@kindex M-n @r{(minibuffer history)}
@findex next-history-element
@findex previous-history-element
  While in the minibuffer, typing @kbd{M-p} or @key{Up}
(@code{previous-history-element}) moves up through the minibuffer
history list, one item at a time.  Each @kbd{M-p} fetches an earlier
item from the history list into the minibuffer, replacing its existing
contents.  Similarly, typing @kbd{M-n} or @key{Down}
(@code{next-history-element}) moves back down the history list,
fetching later entries into the minibuffer.  You can think of these
commands as ``backwards'' and ``forwards'' through the history list.

  If you type @kbd{M-n} in the minibuffer when there are no later
entries in the minibuffer history (e.g., if you haven't previously
typed @kbd{M-p}), Emacs tries fetching from a list of default
argument: values that you are likely to enter.  You can think of this
as moving through the ``future list'' instead of the ``history list''.

  The input that @kbd{M-p} or @kbd{M-n} fetches into the minibuffer
entirely replaces the existing contents of the minibuffer, so you can
simply type @key{RET} to use it as an argument.  You can also edit the
text before you reuse it; this does not change the history element
that you ``moved'' to, but your new argument does go at the end of the
history list in its own right.

@findex previous-matching-history-element
@findex next-matching-history-element
@kindex M-r @r{(minibuffer history)}
@kindex M-s @r{(minibuffer history)}
  There are also commands to search forward or backward through the
history; they search for history elements that match a regular
expression.  @kbd{M-r} (@code{previous-matching-history-element})
searches older elements in the history, while @kbd{M-s}
(@code{next-matching-history-element}) searches newer elements.  These
commands are unusual: they use the minibuffer to read the regular
expression even though they are invoked from the minibuffer.  As with
incremental searching, an upper-case letter in the regular expression
makes the search case-sensitive (@pxref{Search Case}).

  All uses of the minibuffer record your input on a history list, but
there are separate history lists for different kinds of arguments.
For example, there is a list for file names, used by all the commands
that read file names.  (As a special feature, this history list
records the absolute file name, even if the name you entered was not
absolute.)

  There are several other specific history lists, including one for
buffer names, one for arguments of commands like @code{query-replace},
one used by @kbd{M-x} for command names, and one used by
@code{compile} for compilation commands.  Finally, there is one
``miscellaneous'' history list that most minibuffer arguments use.

@vindex history-length
  The variable @code{history-length} specifies the maximum length of a
minibuffer history list; adding a new element deletes the oldest
element if the list gets too long.  If the value of
@code{history-length} is @code{t}, there is no maximum length.

@vindex history-delete-duplicates
  The variable @code{history-delete-duplicates} specifies whether to
delete duplicates in history.  If it is non-@code{nil}, adding a new
element deletes from the list all other elements that are equal to it.
The default is @code{nil}.

@node Repetition
@section Repeating Minibuffer Commands
@cindex command history
@cindex history of commands

  Every command that uses the minibuffer once is recorded on a special
history list, the @dfn{command history}, together with the values of
its arguments, so that you can repeat the entire command.  In
particular, every use of @kbd{M-x} is recorded there, since @kbd{M-x}
uses the minibuffer to read the command name.

@findex list-command-history
@table @kbd
@item C-x @key{ESC} @key{ESC}
Re-execute a recent minibuffer command from the command history
 (@code{repeat-complex-command}).
@item M-x list-command-history
Display the entire command history, showing all the commands
@kbd{C-x @key{ESC} @key{ESC}} can repeat, most recent first.
@end table

@kindex C-x ESC ESC
@findex repeat-complex-command
  @kbd{C-x @key{ESC} @key{ESC}} is used to re-execute a recent command
that used the minibuffer.  With no argument, it repeats the last such
command.  A numeric argument specifies which command to repeat; 1
means the last one, 2 the previous, and so on.

  @kbd{C-x @key{ESC} @key{ESC}} works by turning the previous command
into a Lisp expression and then entering a minibuffer initialized with
the text for that expression.  Even if you don't understand Lisp
syntax, it will probably be obvious which command is displayed for
repetition.  If you type just @key{RET}, that repeats the command
unchanged.  You can also change the command by editing the Lisp
expression before you execute it.  The repeated command is added to
the front of the command history unless it is identical to the most
recently item.

  Once inside the minibuffer for @kbd{C-x @key{ESC} @key{ESC}}, you can
use the minibuffer history commands (@kbd{M-p}, @kbd{M-n}, @kbd{M-r},
@kbd{M-s}; @pxref{Minibuffer History}) to move through the history list
of saved entire commands.  After finding the desired previous command,
you can edit its expression as usual and then repeat it by typing
@key{RET}.

@vindex isearch-resume-in-command-history
  Incremental search does not, strictly speaking, use the minibuffer.
Therefore, although it behaves like a complex command, it normally
does not appear in the history list for @kbd{C-x @key{ESC} @key{ESC}}.
You can make incremental search commands appear in the history by
setting @code{isearch-resume-in-command-history} to a non-@code{nil}
value.  @xref{Incremental Search}.

@vindex command-history
  The list of previous minibuffer-using commands is stored as a Lisp
list in the variable @code{command-history}.  Each element is a Lisp
expression which describes one command and its arguments.  Lisp programs
can re-execute a command by calling @code{eval} with the
@code{command-history} element.

@ignore
   arch-tag: ba913cfd-b70e-400f-b663-22b2c309227f
@end ignore