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7.3.4.4 Single or Numbered Backups

When Emacs makes a backup file, its name is normally constructed by appending ‘~’ to the file name being edited.

Emacs can also make numbered backup files. Numbered backup file names contain ‘.~’, the number, and another ‘~’ after the original file name.

version-control — a variable

determines whether to make single backup files or mul- tiple numbered backup files. The usual way to set this variable is globally, through your init file or the customization buffer. But you can set version-control locally in an individual buffer to control the making of backups for that buffer’s file.

nil

make single backups, unless files already have numbered backups.

t

make numbered backups.

never

never make numbered backups; always make single backups.

make-backup-file-name-function

tell Emacs what function to use to make backup names.