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.\"
.\" Copyright (c) 2003 Joseph Koshy <jkoshy@freebsd.org>
.\" Copyright (c) 2006 Ceri Davies <ceri@FreeBSD.org>
.\"
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 19, 2006
.Dt P_CANSEE 9
.Os
.Sh NAME
.Nm p_cansee
.Nd determine visibility of a process
.Sh SYNOPSIS
.In sys/param.h
.In sys/proc.h
.Ft int
.Fn p_cansee "struct thread *td" "struct proc *p"
.Sh DESCRIPTION
This function can be used to determine if a given process
.Fa p
is visible to the thread
.Fa td ,
where the notion of
.Dq visibility
may be read as
.Dq "awareness of existence" .
.Pp
The function is implemented using
.Xr cr_cansee 9 ,
and the dependencies on
.Xr sysctl 8
variables documented in the
.Xr cr_cansee 9
manual page apply.
.Sh RETURN VALUES
The
.Fn p_cansee
function
returns
.Li 0
if the process denoted by
.Fa p
is visible by thread
.Fa td ,
or a non-zero error return value otherwise.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ESRCH
Process
.Fa p
is not visible to thread
.Fa td
as determined by
.Xr cr_cansee 9 .
.It Bq Er ESRCH
Thread
.Fa td
has been jailed and process
.Fa p
does not belong to the same jail as
.Fa td .
.It Bq Er ESRCH
The MAC subsystem denied visibility.
.El
.Sh SEE ALSO
.Xr jail 2 ,
.Xr sysctl 8 ,
.Xr cr_cansee 9 ,
.Xr mac 9 ,
.Xr p_candebug 9 ,
.Xr prison_check 9
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