.\"
.\" Copyright (c) 1996 Julian Elischer
.\"
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.\" "
.Dd August 15, 1996
.Os
.Dt AT_SHUTDOWN 9
.Sh NAME
.Nm at_shutdown ,
.Nm rm_at_shutdown
.Nd ask that a function be run at shutdown.
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/systm.h>
.Fd #include <sys/reboot.h>
.Ft typedef void \*(lp*bootlist_fn\*(rp\*(lpint howto, void *arg\*(rp

.Ft int
.Fn at_shutdown "bootlist_fn func" "void *arg" "int when"
.Ft int
.Fn rm_at_shutdown "bootlist_fn func" "void *arg"
.Sh DESCRIPTION
The
.Nm at_shutdown
facility allows a kernel module to ensure that it is notified
at system shutdown.
The function
.Ar func
is called with the flags indicating boot type, and the opaque argument
.Ar arg
when the system is shut down.
.Pp
If the requirement for notification is removed, then the function 
.Nm rm_at_shutdown
must be called with the exact
.Ar func
and
.Ar arg
arguments as the corresponding call to
.Fn at_shutdown .
There are two shutdown queues, one run before the final sync and one after.
The last argument to 
.Nm at_shutdown
should be one of 
.Em SHUTDOWN_PRE_SYNC
or
.Em SHUTDOWN_POST_SYNC
to specify which queue should be used.
.Nm rm_at_shutdown
will remove an entry from either queue.
.Pp
.Sh RETURN VALUES
.Nm at_shutdown
returns an error code, 0 meaning success. 
.Nm rm_at_shutdown
returns the number of items removed (should be 0 or 1).
.Sh SEE ALSO
.Xr reboot 2
.Sh HISTORY
The
.Nm at_shutdown
appeared in
.Fx 2.2 .
.Sh BUGS
Since the shutdown queue is not sorted
and items are added to the head, order of execution 
is reversed to that of insertion.
.Sh AUTHORS
The function was written by
.ie t Julian Elischer (julian@freebsd.org)
.el Julian Elischer  (julian@freebsd.org)