.\"
.\" Copyright (c) 1994, Henrik Vestergaard Draboel
.\" All rights reserved.
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.\"    must display the following acknowledgement:
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.\"	$Id$
.\"
.Dd July 23, 1994
.Dt RTPRIO 1
.Os 
.Sh NAME
.Nm rtprio
.Nd execute, examine or modify a utilitys or process realtime scheduling priority
.Sh SYNOPSIS

.Nm rtprio
.Nm rtprio 
.Ar pid
.Nm rtprio 
.Ar priority
.Ar command
.Op args
.Nm rtprio 
.Ar priority
.Ar -pid
.Nm rtprio 
.Ar -t
.Ar command
.Op args
.Nm rtprio 
.Ar -t
.Ar -pid
.Sh DESCRIPTION
.Nm Rtprio
is used for controlling realtime process scheduling. A process with a
realtime priority is not subject to priority degradation, and will only
be preempted by another process of equal or higher realtime priority.

.Nm Rtprio
called without arguments, will return the realtime priority
of the current process.

If
.Nm rtprio
is called with 1 argument, it will return the realtime priority
of the process with the specified
.Ar pid .

If 
.Ar priority
is specified, the process or program is run at that realtime priority.
If 
.Ar -t
is specified, the process or program is run as a normal (non-realtime)
process. 

If
.Ar -pid
is specified, the process with that pid will be modified, else
if 
.Ar command 
is specified, that program is run with its arguments.

.Ar Priority
is an integer between 0 (RTPRIO_MIN) and 31 (RTPRIO_MAX). 0 is the
highest priority

.Ar Pid
of 0 means "the current process".

Only root is allowed to set realtime priorities.
.Sh RETURN VALUE
.Nm rtprio
returns the (new) realtime priority of the process (see rtprio(2)), or
-1 for all usage errors.
.Sh EXAMPLES
.\LP

To see which realtime priority the current process is at:
.Bd -literal -offset indent -compact
\fBrtprio\fP
.Ed

.\.LP
To see which realtime priority of process \fI1423\fP:
.Bd -literal -offset indent -compact
\fBrtprio 1423\fP
.Ed

.\.LP
To run \fIcron\fP at the lowest realtime priority:
.Bd -literal -offset indent -compact
\fBrtprio 31 cron\fP
.Ed

.\.LP
To change the realtime priority of process \fI1423\fP to \fI16\fP:
.Bd -literal -offset indent -compact
\fBrtprio 16 -1423\fP
.Ed

.\.LP
To run \fItcpdump\fP without realtime priority:
.Bd -literal -offset indent -compact
\fBrtprio -t tcpdump\fP
.Ed

.\.LP
To change the realtime priority of process \fI1423\fP to RTRIO_RTOFF
(no realtime):
.Bd -literal -offset indent -compact
\fBrtprio -t -1423\fP
.Ed
.Sh DIAGNOSTICS
The
.Nm rtprio
utility shall exit with value of the (new) realtime priority of the
program.
.Sh SEE ALSO
.Xr rtprio 2 ,
.Xr nice 1 ,
.Xr ps 1 ,
.Xr nice 2 ,
.Xr renice 8
.Sh HISTORY
The
.Nm rtprio
utility appeared in
FreeBSD 2.0,
but is similar to the HP-UX version.
.Sh BUGS
You can lock you're self out of the system, be placing at cpu-heavy
process in a realtime priority.

There is no way to set/view the realtime priority of process 0
(swapper) (see ps(1)).

Others ...
.Sh AUTHOR
Henrik Vestergaard Draboel - hvd@terry.ping.dk