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.\"     @(#)comsat.8	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd January 21, 2010
.Dt COMSAT 8
.Os
.Sh NAME
.Nm comsat
.Nd biff server
.Sh SYNOPSIS
.Nm
.Sh DESCRIPTION
The
.Nm
utility is the server process which receives reports of incoming mail
and notifies users if they have requested this service.
The
.Nm
utility receives messages on a datagram port associated with the
.Dq biff
service
specification (see
.Xr services 5
and
.Xr inetd 8 ) .
The one line messages are of the form:
.Pp
.D1 Ar user Ns @ Ns Ar mailbox Ns - Ns Ar offset Ns Op : Ns Ar mailbox-name
.Pp
If the
.Ar user
specified is logged in to the system and the associated terminal has
the owner execute bit turned on (by a
.Dq Nm biff Cm y ) ,
the
.Ar offset
is used as a seek offset into the appropriate mailbox file and
the first 7 lines or 560 characters of the message are printed
on the user's terminal.
Lines which appear to be part of
the message header other than the
.Dq Li From ,
.Dq Li \&To ,
.Dq Li Date ,
or
.Dq Li Subject
lines are not included in the displayed message.
.Pp
If the
.Ar user
specified is logged in to the system and the associated terminal has
the group execute bit turned on (by a
.Dq Nm biff Cm b ) ,
two bell characters
.Tn ( ASCII
\\007) are printed on the user's terminal.
.Pp
If
.Ar mailbox-name
omitted, standard mailbox assumed.
.Sh FILES
.Bl -tag -width ".Pa /var/mail/user" -compact
.It Pa /var/run/utx.active
to find out who is logged on and on what terminals
.It Pa /var/mail/user
standard mailbox
.El
.Sh SEE ALSO
.Xr biff 1 ,
.Xr inetd 8
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.2 .
.Sh BUGS
The message header filtering is prone to error.
The density of the information presented is near the theoretical minimum.
.Pp
Users should be notified of mail which arrives on other
machines than the one to which they are currently logged in.
.Pp
The notification should appear in a separate window so it
does not mess up the screen.