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.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
.\" USA.
.\"
.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
.\" First version written
.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
.\" revision
.\"
.TH SCHED_SETPARAM 2 "1996-04-10" "Linux 1.3.81" "Linux Programmer's Manual"
.SH NAME
sched_setparam, sched_getparam \- set and get scheduling parameters
.SH SYNOPSIS
.B #include <sched.h>
.sp
\fBint sched_setparam(pid_t \fIpid\fB, const struct sched_param *\fIp\fB);
.sp
\fBint sched_getparam(pid_t \fIpid\fB, struct sched_param *\fIp\fB);
.sp
.nf
.ta 4n
\fBstruct sched_param {
...
int \fIsched_priority\fB;
...
};
.ta
.fi
.SH DESCRIPTION
.B sched_setparam
sets the scheduling parameters associated with the scheduling policy
for the process identified by \fIpid\fR. If \fIpid\fR is zero, then
the parameters of the current process are set. The interpretation of
the parameter \fIp\fR depends on the selected policy. Currently, the
following three scheduling policies are supported under Linux:
.IR SCHED_FIFO ,
.IR SCHED_RR ,
and
.IR SCHED_OTHER.
.B sched_getparam
retrieves the scheduling parameters for the
process identified by \fIpid\fR. If \fIpid\fR is zero, then the parameters
of the current process are retrieved.
.B sched_setparam
checks the validity of \fIp\fR for the scheduling policy of the
process. The parameter \fIp->sched_priority\fR must lie within the
range given by \fBsched_get_priority_min\fR and
\fBsched_get_priority_max\fR.
POSIX systems on which
.B sched_setparam
and
.B sched_getparam
are available define
.I _POSIX_PRIORITY_SCHEDULING
in <unistd.h>.
.SH RETURN VALUE
On success,
.BR sched_setparam
and
.BR sched_getparam
return 0.
On error, \-1 is returned,
.I errno
is set appropriately.
.SH ERRORS
.TP
.B ESRCH
The process whose ID is \fIpid\fR could not be found.
.TP
.B EPERM
The calling process does not have appropriate privileges. The process
calling
.BR sched_setparam
needs an effective uid equal to the euid or uid of the process
identified by
.IR pid ,
or it must be a superuser process.
.TP
.B EINVAL
The parameter \fIp\fR does not make sense for the current
scheduling policy.
.SH "CONFORMING TO"
POSIX.1b (formerly POSIX.4)
.SH SEE ALSO
.BR sched_setscheduler (2),
.BR sched_getscheduler (2),
.BR sched_get_priority_max (2),
.BR sched_get_priority_min (2),
.BR nice (2),
.BR setpriority (2),
.BR getpriority (2),
.PP
.BR sched_setscheduler (2)
has a description of the Linux scheduling scheme.
.PP
.I Programming for the real world \- POSIX.4
by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0
.br
.I IEEE Std 1003.1b-1993
(POSIX.1b standard)
.br
.I ISO/IEC 9945-1:1996
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