Provided by: biff_0.17.pre20000412-5build1_amd64
biff — be notified if mail arrives and who it is from
Biff informs the system whether you want to be notified when mail arrives during the current terminal session. Options supported by biff: n Disables notification. y Enables notification. When mail notification is enabled, the header and first few lines of the message will be printed on your screen whenever mail arrives. A “biff y” command is often included in the file .login or .profile to be executed at each login. Biff operates asynchronously via the comsat(8) service. If that service is not enabled, biff will not do anything. In that case, or for synchronous notification, use the MAIL variable of sh(1) or the mail variable of csh(1).
The biff command appeared in 4.0BSD.
su(1), and biff don't seem to get on too well. This is probably due to the tty still being owned by the person using su. This can result in “Permission denied” messages when attempting to change the biff status of your session. Please report bugs to firstname.lastname@example.org including diffs/patches, compiler error logs or as complete a bug report as is possible.