219 lines
5.7 KiB
Groff
219 lines
5.7 KiB
Groff
.\" $NetBSD: getpriority.2,v 1.4 1995/02/27 12:33:15 cgd Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getpriority.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt GETPRIORITY 2
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.Os BSD 4
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.Sh NAME
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.Nm getpriority ,
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.Nm setpriority
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.Nd get/set program scheduling priority
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.Sh SYNOPSIS
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.Fd #include <sys/resource.h>
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.Ft int
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.Fo getpriority
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.Fa "int which"
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.Fa "id_t who"
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.Fc
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.Ft int
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.Fo setpriority
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.Fa "int which"
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.Fa "id_t who"
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.Fa "int prio"
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.Fc
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.Sh DESCRIPTION
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The scheduling priority of the process, process group, or user as indicated by
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.Fa which
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and
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.Fa who
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is obtained with the
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.Fn getpriority
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call and set with the
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.Fn setpriority
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call.
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.Fa Which
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is one of
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.Dv PRIO_PROCESS ,
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.Dv PRIO_PGRP ,
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or
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.Dv PRIO_USER ,
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and
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.Fa who
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is interpreted relative to
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.Fa which
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(a process identifier for
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.Dv PRIO_PROCESS ,
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process group
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identifier for
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.Dv PRIO_PGRP ,
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and a user ID for
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.Dv PRIO_USER ) .
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A zero value of
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.Fa who
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denotes the current process, process group, or user.
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.Fa prio
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is a value in the range -20 to 20. The default priority is 0;
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lower priorities cause more favorable scheduling.
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.Pp
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The
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.Fn getpriority
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call returns the highest priority (lowest numerical value)
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enjoyed by any of the specified processes.
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The
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.Fn setpriority
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call sets the priorities of all of the specified processes
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to the specified value. Only the super-user may lower priorities.
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.Pp
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Additionally, the current thread or process can be placed in a background state
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by specifying PRIO_DARWIN_THREAD or PRIO_DARWIN_PROCESS for
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.Fa which .
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Only a value of zero (the current thread or process) is supported for
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.Fa who
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when setting or getting background state.
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.Fa prio
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is either 0 (to remove current thread from background status) or PRIO_DARWIN_BG
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(to set current thread into background state).
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When a thread or process is in a background state the scheduling priority is set
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to the lowest value, disk IO is throttled (with behavior similar to using
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.Xr setiopolicy_np 3
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to set a throttleable policy), and network IO is throttled for
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any sockets opened after going into background state. Any previously opened
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sockets are not affected.
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The
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.Fn getpriority
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call returns 0 when current thread or process is not in background state or 1
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when the current thread is in background state. Any thread or process can set
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itself into background state.
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.Sh RETURN VALUES
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Since
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.Fn getpriority
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can legitimately return the value -1, it is necessary
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to clear the external variable
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.Va errno
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prior to the
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call, then check it afterward to determine
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if a -1 is an error or a legitimate value.
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The
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.Fn setpriority
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call returns 0 if there is no error, or
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-1 if there is.
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.Sh ERRORS
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.Fn getpriority
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and
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.Fn setpriority
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will fail if:
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.Bl -tag -width Er
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.\" ==========
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.It Bq Er EINVAL
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.Fa Which
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is not one of
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.Dv PRIO_PROCESS ,
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.Dv PRIO_PGRP ,
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.Dv PRIO_USER ,
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.Dv PRIO_DARWIN_THREAD ,
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or
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.Dv PRIO_DARWIN_PROCESS .
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.\" ==========
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.It Bq Er EINVAL
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.Fa Who
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is not a valid process, process group, or user ID.
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.\" ==========
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.It Bq Er EINVAL
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.Fa Who
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is not 0 when
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.Fa which
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is
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.Dv PRIO_DARWIN_THREAD
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or
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.Dv PRIO_DARWIN_PROCESS .
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.\" ==========
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.It Bq Er ESRCH
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No process can be located using the
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.Fa which
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and
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.Fa who
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values specified.
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.El
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.Pp
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.Bl -tag -width Er
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In addition to the errors indicated above,
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.Fn setpriority
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will fail if:
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.\" ==========
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.It Bq Er EACCES
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A non super-user attempts to lower a process priority.
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.\" ==========
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.It Bq Er EPERM
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A process is located,
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but neither its effective nor real user ID
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matches the effective user ID of the caller.
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.El
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.Sh LEGACY SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/resource.h>
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.Pp
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The include file
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.In sys/types.h
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is necessary.
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.Pp
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.Ft int
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.br
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.Fo getpriority
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.Fa "int which"
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.Fa "int who"
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.Fc ;
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.Pp
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.Ft int
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.br
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.Fo setpriority
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.Fa "int which"
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.Fa "int who"
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.Fa "int value"
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.Fc ;
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.Pp
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The type of
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.Fa who
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has changed.
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.Sh SEE ALSO
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.Xr nice 1 ,
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.Xr fork 2 ,
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.Xr setiopolicy_np 3 ,
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.Xr compat 5 ,
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.Xr renice 8
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.Sh HISTORY
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The
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.Fn getpriority
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function call appeared in
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.Bx 4.2 .
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