23.3.2.1 Numbered Backups

The choice of single backup file or multiple numbered backup files is controlled by the variable version-control. Its possible values are:

t

Make numbered backups.

nil

Make numbered backups for files that have numbered backups already. Otherwise, make single backups.

never

Never make numbered backups; always make single backups.

The usual way to set this variable is globally, through your ‘.emacs’ file or the customization buffer. However, you can set version-control locally in an individual buffer to control the making of backups for that buffer's file. For example, Rmail mode locally sets version-control to never to make sure that there is only one backup for an Rmail file. See section Local Variables.

If you set the environment variable VERSION_CONTROL, to tell various GNU utilities what to do with backup files, Emacs also obeys the environment variable by setting the Lisp variable version-control accordingly at startup. If the environment variable's value is ‘t’ or ‘numbered’, then version-control becomes t; if the value is ‘nil’ or ‘existing’, then version-control becomes nil; if it is ‘never’ or ‘simple’, then version-control becomes never.