Info Catalog elisp: Rename or Copy elisp: Backup Files elisp: Backup Names

elisp: Numbered Backups

 
 25.1.3 Making and Deleting Numbered Backup Files
 ------------------------------------------------
 
 If a file’s name is ‘foo’, the names of its numbered backup versions are
 ‘foo.~V~’, for various integers V, like this: ‘foo.~1~’, ‘foo.~2~’,
 ‘foo.~3~’, ..., ‘foo.~259~’, and so on.
 
  -- User Option: version-control
      This variable controls whether to make a single non-numbered backup
      file or multiple numbered backups.
 
      ‘nil’
           Make numbered backups if the visited file already has numbered
           backups; otherwise, do not.  This is the default.
 
      ‘never’
           Do not make numbered backups.
 
      ANYTHING ELSE
           Make numbered backups.
 
    The use of numbered backups ultimately leads to a large number of
 backup versions, which must then be deleted.  Emacs can do this
 automatically or it can ask the user whether to delete them.
 
  -- User Option: kept-new-versions
      The value of this variable is the number of newest versions to keep
      when a new numbered backup is made.  The newly made backup is
      included in the count.  The default value is 2.
 
  -- User Option: kept-old-versions
      The value of this variable is the number of oldest versions to keep
      when a new numbered backup is made.  The default value is 2.
 
    If there are backups numbered 1, 2, 3, 5, and 7, and both of these
 variables have the value 2, then the backups numbered 1 and 2 are kept
 as old versions and those numbered 5 and 7 are kept as new versions;
 Backup Names::) is responsible for determining which backup versions to
 delete, but does not delete them itself.
 
  -- User Option: delete-old-versions
      If this variable is ‘t’, then saving a file deletes excess backup
      versions silently.  If it is ‘nil’, that means to ask for
      confirmation before deleting excess backups.  Otherwise, they are
      not deleted at all.
 
  -- User Option: dired-kept-versions
      This variable specifies how many of the newest backup versions to
      keep in the Dired command ‘.’ (‘dired-clean-directory’).  That’s
      the same thing ‘kept-new-versions’ specifies when you make a new
      backup file.  The default is 2.
 

Info Catalog elisp: Rename or Copy elisp: Backup Files elisp: Backup Names