* Moving Point:: How to move the cursor to the place where you want to
change something.
* Erasing:: Deleting and killing text.
-* Undo:: Undoing recent changes in the text.
+* Basic Undo:: Undoing recent changes in the text.
* Files: Basic Files. Visiting, creating, and saving files.
* Help: Basic Help. Asking what a character does.
* Blank Lines:: Commands to make or delete blank lines.
@xref{Killing}, for more flexible ways of killing text.
-@node Undo
+@node Basic Undo
@section Undoing Changes
-@cindex undo
-@cindex changes, undoing
- You can undo all the recent changes in the buffer text, up to a
-certain point. Each buffer records changes individually, and the undo
-command always applies to the current buffer. Usually each editing
-command makes a separate entry in the undo records, but some commands
-such as @code{query-replace} make many entries, and very simple commands
-such as self-inserting characters are often grouped to make undoing less
-tedious.
+ Emacs records a list of changes made in the buffer text, so you can
+you can undo all the recent changes, as far as the records go.
+Usually each editing command makes a separate entry in the undo
+records, but sometimes an entry covers just part of a command, and
+very simple commands may be grouped.
@table @kbd
@item C-x u
-Undo one batch of changes---usually, one command worth (@code{undo}).
+Undo one entry of the undo records---usually, one command worth
+(@code{undo}).
@item C-_
@itemx C-/
The same.
@end table
-@kindex C-x u
-@kindex C-_
-@kindex C-/
-@findex undo
The command @kbd{C-x u} (or @kbd{C-_} or @kbd{C-/}) is how you undo.
The first time you give this command, it undoes the last change.
Point moves back to where it was before the command that made the
change.
- Consecutive repetitions of @kbd{C-_} or @kbd{C-x u} undo earlier and
-earlier changes, back to the limit of the undo information available.
-If all recorded changes have already been undone, the undo command
-displays an error message and does nothing.
-
-@findex undo-only
- Any command other than an undo command breaks the sequence of undo
-commands. Starting from that moment, the previous undo commands become
-ordinary changes that you can undo. Thus, to redo changes you have
-undone, type @kbd{C-f} or any other command that will harmlessly break
-the sequence of undoing, then type more undo commands. On the other
-hand, if you want to ignore previous undo commands, use @kbd{M-x
-undo-only}. This is like @code{undo}, but will not redo changes
-you have just undone.
-
- If you notice that a buffer has been modified accidentally, the
-easiest way to recover is to type @kbd{C-_} repeatedly until the stars
-disappear from the front of the mode line. At this time, all the
-modifications you made have been canceled. Whenever an undo command
-makes the stars disappear from the mode line, it means that the buffer
-contents are the same as they were when the file was last read in or
-saved.
-
- If you do not remember whether you changed the buffer deliberately,
-type @kbd{C-_} once. When you see the last change you made undone, you
-will see whether it was an intentional change. If it was an accident,
-leave it undone. If it was deliberate, redo the change as described
-above.
-
- Normal undo applies to the buffer as a whole. You can also
-selectively undo changes in any part of the buffer (@pxref{Selective
-Undo}).
-
- Some specialized buffers do not record undo information. Buffers
-whose names start with spaces never do; these buffers are used
-internally by Emacs and its extensions to hold text that users don't
-normally look at or edit.
+ Consecutive repetitions of @kbd{C-x u} (or its aliases) undo earlier
+and earlier changes, back to the limit of the undo information
+available. If all recorded changes have already been undone, the undo
+command displays an error message and does nothing.
The undo command applies only to changes in the buffer; you can't
use it to undo mere cursor motion. However, some cursor motion
you can move back to the neighborhoods you have moved through by
popping the mark ring (@pxref{Mark Ring}).
-@vindex undo-limit
-@vindex undo-strong-limit
-@vindex undo-outer-limit
-@cindex undo limit
- When the undo information for a buffer becomes too large, Emacs
-discards the oldest undo information from time to time (during garbage
-collection). You can specify how much undo information to keep by
-setting three variables: @code{undo-limit}, @code{undo-strong-limit},
-and @code{undo-outer-limit}. Their values are expressed in units of
-bytes of space.
-
- The variable @code{undo-limit} sets a soft limit: Emacs keeps undo
-data for enough commands to reach this size, and perhaps exceed it,
-but does not keep data for any earlier commands beyond that. Its
-default value is 20000. The variable @code{undo-strong-limit} sets a
-stricter limit: a previous command (not the most recent one) which
-pushes the size past this amount is itself forgotten. The default
-value of @code{undo-strong-limit} is 30000.
-
- Regardless of the values of those variables, the most recent change
-is never discarded unless it gets bigger than @code{undo-outer-limit}
-(normally 3,000,000). At that point, Emacs discards the undo data and
-warns you about it. This is the only situation in which you cannot
-undo the last command. If this happens, you can increase the value of
-@code{undo-outer-limit} to make it even less likely to happen in the
-future. But if you didn't expect the command to create such large
-undo data, then it is probably a bug and you should report it.
-@xref{Bugs,, Reporting Bugs}.
-
- The reason the @code{undo} command has three key bindings, @kbd{C-x
-u}, @kbd{C-_} and @kbd{C-/}, is that it is worthy of a
-single-character key, but @kbd{C-x u} is more straightforward for
-beginners to type. Meanwhile, @kbd{C--} on a text-only terminal is
-really @kbd{C-_}, which makes it a natural and easily typed binding
-for undoing.
-
@node Basic Files
@section Files
projects / emacs.git / commitdiff