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.\" Copyright (c) 2003 Joseph Koshy <jkoshy@FreeBSD.org>
.\" Copyright (c) 2006 Ceri Davies <ceri@FreeBSD.org>
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.\" $FreeBSD: head/share/man/man9/p_cansee.9 208291 2010-05-19 08:57:53Z uqs $
.\"
.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