Biff
lastmod 2026-11-10created 2025-12-042 edits
biff is a command on Unix-like systems that sets whether to show a notification in the terminal when new mail arrives. biff y turns notifications on, biff n turns them off, and running it without arguments shows the current state. It is an old tool that works together with the comsat daemon, which watches for incoming mail; it is rarely used today but is introduced alongside terminal messaging commands such as mesg, wall, and write.