man2/sched_setparam.2

.\" 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@gmail.com>
.\"
.TH SCHED_SETPARAM 2 2021-03-22 "Linux" "Linux Programmer's Manual"
.SH NAME
sched_setparam, sched_getparam \- set and get scheduling parameters
.SH SYNOPSIS
.nf
.B #include <sched.h>
.PP
.BI "int sched_setparam(pid_t " pid ", const struct sched_param *" param );
.BI "int sched_getparam(pid_t " pid ", struct sched_param *" param );
.PP
\fBstruct sched_param {
    ...
    int \fIsched_priority\fB;
    ...
};
.fi
.SH DESCRIPTION
.BR sched_setparam ()
sets the scheduling parameters associated with the scheduling policy
for the thread whose thread ID is specified in \fIpid\fP.
If \fIpid\fP is zero, then
the parameters of the calling thread are set.
The interpretation of
the argument \fIparam\fP depends on the scheduling
policy of the thread identified by
.IR pid .
See
.BR sched (7)
for a description of the scheduling policies supported under Linux.
.PP
.BR sched_getparam ()
retrieves the scheduling parameters for the
thread identified by \fIpid\fP.
If \fIpid\fP is zero, then the parameters
of the calling thread are retrieved.
.PP
.BR sched_setparam ()
checks the validity of \fIparam\fP for the scheduling policy of the
thread.
The value \fIparam\->sched_priority\fP must lie within the
range given by
.BR sched_get_priority_min (2)
and
.BR sched_get_priority_max (2).
.PP
For a discussion of the privileges and resource limits related to
scheduling priority and policy, see
.BR sched (7).
.PP
POSIX systems on which
.BR sched_setparam ()
and
.BR sched_getparam ()
are available define
.B _POSIX_PRIORITY_SCHEDULING
in \fI<unistd.h>\fP.
.SH RETURN VALUE
On success,
.BR sched_setparam ()
and
.BR sched_getparam ()
return 0.
On error, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EINVAL
Invalid arguments:
.I param
is NULL or
.I pid
is negative
.TP
.B EINVAL
.RB ( sched_setparam ())
The argument \fIparam\fP does not make sense for the current
scheduling policy.
.TP
.B EPERM
.RB ( sched_setparam ())
The caller does not have appropriate privileges
(Linux: does not have the
.B CAP_SYS_NICE
capability).
.TP
.B ESRCH
The thread whose ID is \fIpid\fP could not be found.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH SEE ALSO
.ad l
.nh
.BR getpriority (2),
.BR gettid (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_setattr (2),
.BR sched_setscheduler (2),
.BR setpriority (2),
.BR capabilities (7),
.BR sched (7)