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 Locals.

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.