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Info Node: (emacs)Reverting

(emacs)Reverting


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Reverting a Buffer
==================

   If you have made extensive changes to a file and then change your
mind about them, you can get rid of them by reading in the previous
version of the file.  To do this, use `M-x revert-buffer', which
operates on the current buffer.  Since reverting a buffer
unintentionally could lose a lot of work, you must confirm this command
with `yes'.

   `revert-buffer' keeps point at the same distance (measured in
characters) from the beginning of the file.  If the file was edited only
slightly, you will be at approximately the same piece of text after
reverting as before.  If you have made drastic changes, the same value
of point in the old file may address a totally different piece of text.

   Reverting marks the buffer as "not modified" until another change is
made.

   Some kinds of buffers whose contents reflect data bases other than
files, such as Dired buffers, can also be reverted.  For them,
reverting means recalculating their contents from the appropriate data
base.  Buffers created explicitly with `C-x b' cannot be reverted;
`revert-buffer' reports an error when asked to do so.

   When you edit a file that changes automatically and frequently--for
example, a log of output from a process that continues to run--it may be
useful for Emacs to revert the file without querying you, whenever you
visit the file again with `C-x C-f'.

   To request this behavior, set the variable `revert-without-query' to
a list of regular expressions.  When a file name matches one of these
regular expressions, `find-file' and `revert-buffer' will revert it
automatically if it has changed--provided the buffer itself is not
modified.  (If you have edited the text, it would be wrong to discard
your changes.)

   You may find it useful to have Emacs revert files automatically when
they change.  Two minor modes are available to do this.  In Global
Auto-Revert mode, Emacs periodically checks all file buffers and
reverts any when the corresponding file has changed.  The local
variant, Auto-Revert mode, applies only to buffers in which it was
activated.  Checking the files is done at intervals determined by the
variable `auto-revert-interval'.


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