GNU Emacs

18.6 Auto-Saving: Protection Against Disasters

From time to time, Emacs automatically saves each visited file in a separate file, without altering the file you actually use. This is called auto-saving. It prevents you from losing more than a limited amount of work if the system crashes.

When Emacs determines that it is time for auto-saving, it considers each buffer, and each is auto-saved if auto-saving is enabled for it and it has been changed since the last time it was auto-saved. When the auto-save-no-message variable is set to nil (the default), the message ‘ Auto-saving...’ is displayed in the echo area during auto-saving, if any files are actually auto-saved; to disable these messages, customize the variable to a non- nil value. Errors occurring during auto-saving are caught so that they do not interfere with the execution of commands you have been typing.