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.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
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.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
.\"            First version written
.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
.\"            revision
.\" Modified 2004-05-27 by Michael Kerrisk <mtk-manpages@gmx.net>
.\"
.TH SCHED_SETPARAM 2 2005-07-28 "Linux 2.6.12" "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.

For a discussion of the privileges and resource limits related to 
scheduling priority and policy, see
.BR sched_setscheduler (2).

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 EINVAL
The parameter \fIp\fR does not make sense for the current
scheduling policy.
.TP
.B EPERM
The calling process does not have appropriate privileges
(Linux: does not have the
.B CAP_SYS_NICE
capability).
.TP
.B ESRCH
The process whose ID is \fIpid\fR could not be found.
.SH "CONFORMING TO"
POSIX.1b (formerly POSIX.4)
.SH "SEE ALSO"
.BR getpriority (2),
.BR nice (2),
.BR sched_get_priority_max (2),
.BR sched_get_priority_min (2),
.BR sched_getaffinity (2),
.BR sched_getscheduler (2),
.BR sched_setaffinity (2),
.BR sched_setscheduler (2),
.BR setpriority (2),
.BR capabilities (7)
.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