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[sxemacs] / info / sxemacs / mark.texi

@node Mark, Mouse Selection, Help, Top
@chapter Selecting Text
@cindex mark
@cindex region

  Many Emacs commands operate on an arbitrary contiguous
part of the current buffer. You can select text in two ways:

@itemize @bullet
@item
You use special keys to select text by defining a region between point
and the mark.
@item
If you are running SXEmacs under X, you can also select text
with the mouse.
@end itemize

@section The Mark and the Region
 To specify the text for a command to operate on, set @dfn{the
mark} at one end of it, and move point to the other end.  The text
between point and the mark is called @dfn{the region}.  You can move
point or the mark to adjust the boundaries of the region.  It doesn't
matter which one is set first chronologically, or which one comes
earlier in the text.

  Once the mark has been set, it remains until it is set again at
another place.  The mark remains fixed with respect to the preceding
character if text is inserted or deleted in a buffer.  Each Emacs
buffer has its own mark; when you return to a buffer that had been
selected previously, it has the same mark it had before.

  Many commands that insert text, such as @kbd{C-y} (@code{yank}) and
@kbd{M-x insert-buffer}, position the mark at one end of the inserted
text---the opposite end from where point is positioned, so that the region
contains the text just inserted.

  Aside from delimiting the region, the mark is useful for marking
a spot that you may want to go back to.  To make this feature more useful,
Emacs remembers 16 previous locations of the mark in the @code{mark ring}.

@menu
* Setting Mark::        Commands to set the mark.
* Using Region::        Summary of ways to operate on contents of the region.
* Marking Objects::     Commands to put region around textual units.
* Mark Ring::           Previous mark positions saved so you can go back there.
@end menu

@node Setting Mark, Using Region, Mark, Mark
@subsection Setting the Mark

  Here are some commands for setting the mark:

@c WideCommands
@table @kbd
@item C-@key{SPC}
Set the mark where point is (@code{set-mark-command}).
@item C-@@
The same.
@item C-x C-x
Interchange mark and point (@code{exchange-point-and-mark}).
@item C-<
Pushes a mark at the beginning of the buffer.
@item C->
Pushes a mark at the end of the buffer.
@end table

  For example, to convert part of the buffer to all
upper-case, you can use the @kbd{C-x C-u} (@code{upcase-region})
command, which operates on the text in the region.  First go to the
beginning of the text you want to capitalize and type @kbd{C-@key{SPC}} to
put the mark there, then move to the end, and then type @kbd{C-x C-u} to
capitalize the selected region.  You can also set the mark at the end of the
text, move to the beginning, and then type @kbd{C-x C-u}.  Most commands
that operate on the text in the region have the word @code{region} in
their names.

@kindex C-SPC
@findex set-mark-command
  The most common way to set the mark is with the @kbd{C-@key{SPC}}
command (@code{set-mark-command}).  This command sets the mark where
point is. You can then move point away, leaving the mark behind.  It is
actually incorrect to speak of the character @kbd{C-@key{SPC}}; there is
no such character.  When you type @key{SPC} while holding down
@key{CTRL}, you get the character @kbd{C-@@} on most terminals. This
character is actually bound to @code{set-mark-command}.  But unless you are
unlucky enough to have a terminal where typing @kbd{C-@key{SPC}} does
not produce @kbd{C-@@}, you should think of this character as
@kbd{C-@key{SPC}}.

@kindex C-x C-x
@findex exchange-point-and-mark
  Since terminals have only one cursor, Emacs cannot show you where the
mark is located. Most people use the mark soon after they set it, before
they forget where it is. But you can see where the mark is with the
command @kbd{C-x C-x} (@code{exchange-point-and-mark}) which puts the
mark where point was and point where the mark was.  The extent of the
region is unchanged, but the cursor and point are now at the previous
location of the mark.

@kindex C-<
@kindex C->
@findex mark-beginning-of-buffer
@findex mark-end-of-buffer
 Another way to set the mark is to push the mark to the beginning of a
buffer while leaving point at its original location. If you supply an
argument to @kbd{C-<} (@code{mark-beginning-of-buffer}), the mark is pushed
@var{n}/10 of the way from the true beginning of the buffer. You can
also set the mark at the end of a buffer with @kbd{C->}
(@code{mark-end-of-buffer}). It pushes the mark to the end of the buffer,
leaving point alone. Supplying an argument to the command pushes the mark
@var{n}/10 of the way from the true end of the buffer.

If you are using SXEmacs under the X window system, you can set
the variable @code{zmacs-regions} to @code{t}. This makes the current
region (defined by point and mark) highlight and makes it available as
the X clipboard selection, which means you can use the menu bar items on
it.  @xref{Active Regions}, for more information.

  @kbd{C-x C-x} is also useful when you are satisfied with the location of
point but want to move the mark; do @kbd{C-x C-x} to put point there and
then you can move it.  A second use of @kbd{C-x C-x}, if necessary, puts
the mark at the new location with point back at its original location.

@node Using Region, Marking Objects, Setting Mark, Mark
@subsection Operating on the Region

  Once you have created an active region, you can do many things to
the text in it:
@itemize @bullet
@item
Kill it with @kbd{C-w} (@pxref{Killing}).
@item
Save it in a register with @kbd{C-x r s} (@pxref{Registers}).
@item
Save it in a buffer or a file (@pxref{Accumulating Text}).
@item
Convert case with @kbd{C-x C-l} or @kbd{C-x C-u} @*(@pxref{Case}).
@item
Evaluate it as Lisp code with @kbd{M-x eval-region} (@pxref{Lisp Eval}).
@item
Fill it as text with @kbd{M-q} (@pxref{Filling}).
@item
Print hardcopy with @kbd{M-x print-region} (@pxref{Hardcopy}).
@item
Indent it with @kbd{C-x @key{TAB}} or @kbd{C-M-\} (@pxref{Indentation}).
@end itemize

@node Marking Objects, Mark Ring, Using Region, Mark
@subsection Commands to Mark Textual Objects

  There are commands for placing point and the mark around a textual
object such as a word, list, paragraph or page.

@table @kbd
@item M-@@
Set mark after end of next word (@code{mark-word}).  This command and
the following one do not move point.
@item C-M-@@
Set mark after end of next Lisp expression (@code{mark-sexp}).
@item M-h
Put region around current paragraph (@code{mark-paragraph}).
@item C-M-h
Put region around current Lisp defun (@code{mark-defun}).
@item C-x h
Put region around entire buffer (@code{mark-whole-buffer}).
@item C-x C-p
Put region around current page (@code{mark-page}).
@end table

@kindex M-@@
@kindex C-M-@@
@findex mark-word
@findex mark-sexp
@kbd{M-@@} (@code{mark-word}) puts the mark at the end of the next word,
while @kbd{C-M-@@} (@code{mark-sexp}) puts it at the end of the next Lisp
expression. These characters sometimes save you some typing.

@kindex M-h
@kindex C-M-h
@kindex C-x C-p
@kindex C-x h
@findex mark-paragraph
@findex mark-defun
@findex mark-page
@findex mark-whole-buffer
   A number of commands are available that set both point and mark and
thus delimit an object in the buffer.  @kbd{M-h} (@code{mark-paragraph})
moves point to the beginning of the paragraph that surrounds or follows
point, and puts the mark at the end of that paragraph
(@pxref{Paragraphs}).  You can then indent, case-convert, or kill the
whole paragraph.  In the same fashion, @kbd{C-M-h} (@code{mark-defun})
puts point before and the mark after the current or following defun
(@pxref{Defuns}).  @kbd{C-x C-p} (@code{mark-page}) puts point before
the current page (or the next or previous, depending on the argument),
and mark at the end (@pxref{Pages}).  The mark goes after the
terminating page delimiter (to include it), while point goes after the
preceding page delimiter (to exclude it).  Finally, @kbd{C-x h}
(@code{mark-whole-buffer}) sets up the entire buffer as the region by
putting point at the beginning and the mark at the end.

@node Mark Ring,, Marking Objects, Mark
@subsection The Mark Ring

@kindex C-u C-SPC
@cindex mark ring
@kindex C-u C-@@
  Aside from delimiting the region, the mark is also useful for marking
a spot that you may want to go back to.  To make this feature more
useful, Emacs remembers 16 previous locations of the mark in the
@dfn{mark ring}.  Most commands that set the mark push the old mark onto
this ring.  To return to a marked location, use @kbd{C-u C-@key{SPC}}
(or @kbd{C-u C-@@}); this is the command @code{set-mark-command} given a
numeric argument.  The command moves point to where the mark was, and
restores the mark from the ring of former marks. Repeated use of this
command moves point to all the old marks on the ring, one by one.
The marks you have seen go to the end of the ring, so no marks are lost.

  Each buffer has its own mark ring.  All editing commands use the current
buffer's mark ring.  In particular, @kbd{C-u C-@key{SPC}} always stays in
the same buffer.

  Many commands that can move long distances, such as @kbd{M-<}
(@code{beginning-of-buffer}), start by setting the mark and saving the
old mark on the mark ring.  This makes it easier for you to move back
later.  Searches set the mark, unless they do not actually move point.
When a command sets the mark, @samp{Mark Set} is printed in the
echo area.

@vindex mark-ring-max
  The variable @code{mark-ring-max} is the maximum number of entries to
keep in the mark ring.  If that many entries exist and another entry is
added, the last entry in the list is discarded.  Repeating @kbd{C-u
C-@key{SPC}} circulates through the entries that are currently in the
ring.

@vindex mark-ring
  The variable @code{mark-ring} holds the mark ring itself, as a list of
marker objects in the order most recent first.  This variable is local
in every buffer.