biff is a mail

E-mail

Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

 notification system for UNIX

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

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Usage

When a new mail message is delivered, the program biff alerts the recipient so he can read it immediately. The alert is sent to the tty where the recipient is logged in, and contains the Subject, From line, and first few lines of the body of the new message. The alert also includes terminal beeps to guarantee quick attention.

Notification is enabled by the command

biff y

and disabled by

biff n

Replacements

Because the sudden, unexpected printing of a block of text on a tty can be annoying if it overwrites more useful information on the screen that can't be easily regenerated, biff is not used very much any more. Some modern MTA

Mail transfer agent

Within Internet message handling services , a message transfer agent or mail transfer agent or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture...

s do not even support comsat, making biff useless.

The general idea of the incoming mail alert has remained very popular even as the original biff and comsat have been almost completely abandoned. There are many biff replacements, several with similar names like xbiff

Xbiff

xbiff is a small utility for the X Window System that shows a mailbox with its flag raised whenever the user has new e-mail. It is included in almost every X Window System....

, xlbiff, kbiff, gnubiff, wmbiff, imapbiff and xbuffy. The concept also extends outside the UNIX world — the AOL

AOL

AOL Inc. is an American global Internet services and media company. AOL is headquartered at 770 Broadway in New York. Founded in 1983 as Control Video Corporation, it has franchised its services to companies in several nations around the world or set up international versions of its services...

 "You've got mail" voice could be seen as a talking biff.

Variant

Some versions of biff, such as the one found in FreeBSD as of 4.7 have a third mode of operation. In addition to y and n it could be set to b which would reduce the alert to just a pair of beeps, without any text written to the terminal. This makes biff less disruptive.

Origin and name

Biff came from 4.0BSD

Berkeley Software Distribution

Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...

, and was named after a dog known by the developers at Berkeley, who – according to the UNIX manual page – died on the 15th August 1993, at the age of 15, and belonged to a certain Heidi Stettner.

Some sources report that the dog would bark at the mail carrier, making it a natural choice for the name of a mail notification system. The Jargon File

Jargon File

The Jargon File is a glossary of computer programmer slang. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab and others of the old ARPANET AI/LISP/PDP-10 communities, including Bolt, Beranek and Newman, Carnegie Mellon...

contradicts this description, but confirms at least that the dog existed.