biff

Enable mail notification for the current terminal session

$ biff y

$ biff n

$ biff

biff [y | n]

biff is a mail notification utility that informs you at the command line when new mail arrives during your terminal session. When enabled, it displays the sender, subject, and the first few lines of incoming messages along with a terminal beep.
The notification works asynchronously through the comsat(8) service. If comsat is not enabled on the system, biff will have no effect. For synchronous notification, use the MAIL variable in sh(1) or the mail variable in csh(1) instead.
A common practice is to include biff y in ~/.login or ~/.profile to enable notifications at each login.

y

Enable mail notification for the current terminal

Disable mail notification for the current terminal

The biff command requires the comsat(8) daemon to be running on the system. Without it, mail notifications will not work.
Using su(1) can cause permission issues with biff due to terminal ownership remaining with the original user, resulting in "Permission denied" errors when changing notification status.

The command is named after Biff, a dog belonging to one of the developers at the University of California, Berkeley during the development of BSD 4.0 in the late 1970s. Biff was known for barking at the mail carrier, making the name a fitting choice for a mail notification utility.

mail(1), sh(1), csh(1)