.\"
.\" Copyright (c) 1996 Julian Elischer
.\"
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.\" $FreeBSD: src/share/man/man9/at_fork.9,v 1.9.2.7 2002/01/10 09:36:27 ru Exp $
.\"
.Dd August 15, 1996
.Dt AT_FORK 9
.Os
.Sh NAME
.Nm at_fork ,
.Nm rm_at_fork
.Nd ask that a function be run at fork
.Sh SYNOPSIS
.In sys/types.h
.In sys/systm.h
.Ft "typedef void"
.Fn (*forklist_fn) "struct proc *" "struct proc *" int
.Pp
.Ft int
.Fn at_fork "forklist_fn func"
.Ft int
.Fn rm_at_fork "forklist_fn func"
.Sh DESCRIPTION
The
.Nm
facility allows a kernel module to ensure that it is notified
at any process fork.
The function
.Fa func
is called with the a pointer to the forking process's proc structure,
a pointer to the child's process structure and a flag word,
as used in
.Xr rfork 2
to indicate the type of fork.
.Pp
If the requirement for notification is removed, then the function
.Fn rm_at_fork
must be called with the exact
.Fa func
argument as the corresponding call to
.Fn at_fork .
.Sh RETURN VALUES
.Fn at_fork
returns an
.Va errno ,
0 meaning success.
.Fn rm_at_fork
returns the number of items removed (should be 0 or 1).
.Sh SEE ALSO
.Xr fork 2
.Sh HISTORY
The
.Fn at_fork
function appeared in
.Fx 2.2 .
.Sh AUTHORS
The function was written by
.An Julian Elischer Aq Mt julian@FreeBSD.org .