Merge from emacs--rel--22

[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 (anything more a single number).  We call it the
``minibuffer'' because it's a special-purpose buffer with a small
amount of screen space.  Minibuffer arguments can be file names,
buffer names, Lisp function names, Emacs command names, Lisp
expressions, and many other things---whatever the command wants to
read.  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; it says what kind of input is expected and how it will
be used.  Often the prompt is derived from the name of the command
that is reading the argument.  The prompt normally ends with a colon.

@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 show a buffer name as the default.  You can type
@key{RET} to operate on that default buffer.

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

  Since the minibuffer appears in the echo area, it can conflict with
other uses of the echo area.  Here is how Emacs handles such
conflicts:

@itemize @bullet
@item
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.

@item
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.

@item
Keystrokes don't echo while the minibuffer is in use.
@end itemize

@menu
* File: Minibuffer File.  Entering file names with the minibuffer.
* Edit: 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

  When you use the minibuffer to enter a file name, it starts out with
some initial text---the @dfn{default directory}, ending in a slash.
The file you specify will be in this directory unless you alter or
replace it.

@c Separate paragraph to clean up ugly page break--rms
@need 1500
  For example, if the minibuffer starts out with these contents:

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

@noindent
(where @samp{Find File:@: } is the prompt), and you type
@kbd{buffer.c} as input, that specifies the file
@file{/u2/emacs/src/buffer.c}.  You can specify the parent directory
by adding @file{..}; thus, if you type @kbd{../lisp/simple.el}, you
will get @file{/u2/emacs/lisp/simple.el}.  Alternatively, you can use
@kbd{M-@key{DEL}} to kill the directory names you don't want
(@pxref{Words}).

  You can kill the entire default with @kbd{C-a C-k}, but there's no
need to do that.  It's easier to ignore the default, and enter an
absolute file name starting with a slash or a tilde after the default
directory.  For example, to specify @file{/etc/termcap}, just type
that name:

@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
GNU Emacs interprets a double slash (which is not normally useful in
file names) as, ``ignore everything before the second slash in the
pair.''  In the example above. @samp{/u2/emacs/src/} is ignored, so
you get @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 (a minor mode) with the command
@kbd{M-x file-name-shadow-mode}.

  If the variable @code{insert-default-directory} is @code{nil}, the
default directory is never inserted in the minibuffer---so 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.

  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.)

  The minibuffer has its own window, which normally has space in the
frame at all times, but it only acts like an Emacs window when the
minibuffer is active.  When active, this window is much like any other
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 then yank the text into the argument.
@xref{Windows}.

@cindex height of minibuffer
@cindex size of minibuffer
@cindex growing minibuffer
@cindex resizing minibuffer
  There are some restrictions on the minibuffer window, however: you
cannot kill it, or split it, or switch buffers in it---the minibuffer
and its window are permanently attached.

@vindex resize-mini-windows
  The minibuffer window expands vertically as necessary to hold the
text that you put in the minibuffer.  If @code{resize-mini-windows} is
@code{t}, the window always resizes as needed by its contents.  If its
value is the symbol @code{grow-only} (the default), the window grows
automatically as needed, but shrinks (back to the normal size) only
when the minibuffer becomes inactive.  If its value is @code{nil}, you
have to adjust the height yourself.

@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.  (Entering the minibuffer from the
minibuffer can be confusing.)  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
  
  Some arguments allow @dfn{completion} to enter their value.  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---@key{TAB}, @key{RET},
and @key{SPC}---are rebound to complete the text in the minibuffer
before point into a longer string chosen from a set of @dfn{completion
alternatives} provided by the command that requested the argument.
(@key{SPC} does not do completion in reading file names, because it is
common to use spaces in file names on some systems.)  @kbd{?} displays
a list of the possible completions at any time.

  For example, @kbd{M-x} uses the minibuffer to read the name of a
command, so it provides a list of all Emacs command names for
completion candidates.  The completion keys match the minibuffer text
against these candidates, find any additional name characters implied
by the text already present in the minibuffer, and add those
characters.  This makes it possible to type @kbd{M-x ins @key{SPC} b
@key{RET}} instead of @kbd{M-x insert-buffer @key{RET}}, for example.

  Case is significant in completion when it is significant in the
argument you are entering (buffer names, file names, command names,
for instance).  Thus, @samp{fo} does not complete to @samp{Foo}.
Completion ignores case distinctions for certain arguments in which
case does not matter.

  Completion acts only on the text before point.  If there is text in
the minibuffer after point---i.e., if you move point backward after
typing some text into the minibuffer---it remains unchanged.

@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 au
@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{auto-save-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 any of @samp{cfilrs}.  So it does not add
any characters; instead, @key{TAB} displays a list of all possible
completions in another window.

  Now type @kbd{f @key{TAB}}.  This @key{TAB} sees @samp{auto-f}.  The
only command name starting with that is @code{auto-fill-mode}, so
completion fills in the rest of that.  You have been able to enter
@samp{auto-fill-mode} by typing just @kbd{au @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
(@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
@iftex
in the next subsection (@code{minibuffer-complete-and-exit}).
@end iftex
@ifnottex
in the next 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} 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}.  The command that implements this behavior is
called @code{minibuffer-complete-word}.

  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}).  You must click in the
list of completions, not in the minibuffer.

@findex switch-to-completions
@item @key{PRIOR}
@itemx M-v
Typing @key{PRIOR} or @key{PAGE-UP}, or @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.  (Selecting that window in other ways has the same
effect.)

@findex choose-completion
@item @key{RET}
Typing @key{RET} @emph{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} @emph{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} @emph{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-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"}, @code{".dvi"} and
@code{"~"}.  The effect is that, for example, @samp{foo} can complete
to @samp{foo.c} even though @samp{foo.o} exists as well.  However, if
@emph{all} the possible completions end in ``ignored'' strings, then
they are not ignored.  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; then that directory and
its contents are ignored.  Elements of
@code{completion-ignored-extensions} which do not end in a slash are
ordinary file names, and do not apply to names of directories.

@vindex completion-auto-help
  If @code{completion-auto-help} is set to @code{nil}, the completion
commands never display a list of possibilities; you must type @kbd{?}
to display the list.

@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 on a
@dfn{minibuffer history list} so you can easily use it again later.
Special commands fetch the text of an earlier argument into the
minibuffer, replacing the old minibuffer contents.  You can think of
them as moving through the history of previous arguments.

@table @kbd
@item @key{UP}
@itemx M-p
Move to the previous item in the minibuffer history, an earlier argument
(@code{previous-history-element}).
@item @key{DOWN}
@itemx M-n
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
  To move through the minibuffer history list one item at a time, use
@kbd{M-p} or up-arrow (@code{previous-history-element}) to fetch the
next earlier minibuffer input, and use @kbd{M-n} or down-arrow
(@code{next-history-element}) to fetch the next later input.  These
commands don't move the cursor, they pull different saved strings into
the minibuffer.  But you can think of them as ``moving'' through the
history list.

  The input that you fetch from the history entirely replaces the
contents of the minibuffer.  To use it again unchanged, just type
@key{RET}.  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.

  For many minibuffer arguments there is a ``default'' value, or
a list of default values.  You can insert the default value into the
minibuffer as text by using @kbd{M-n} one or more times.  You can
think of this as moving ``into the future'' in the history.

@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}).

@ignore
  We may change the precise way these commands read their arguments.
Perhaps they will search for a match for the string given so far in the
minibuffer; perhaps they will search for a literal match rather than a
regular expression match; perhaps they will only accept matches at the
beginning of a history element; perhaps they will read the string to
search for incrementally like @kbd{C-s}.  To find out what interface is
actually available, type @kbd{C-h f previous-matching-history-element}.
@end ignore

  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}, though, 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 @code{t}, adding a new element
deletes from the list all other elements that are equal to it.

@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