sched_setparam()

Change the priority of a process

Synopsis:

#include <sched.h>

int sched_setparam( 
          pid_t pid,
          const struct sched_param *param );

Arguments:

pid

The ID of the process whose priority you want to set, or 0 to set it for the current process.

param

A pointer to a sched_param structure whose sched_priority member holds the priority that you want to assign to the process.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The sched_setparam() function changes the priority of process pid to that of the sched_priority member in the sched_param structure pointed to by param. If pid is zero, the priority of the calling process is changed.

The sched_priority member in param must lie between the minimum and maximum values returned by sched_get_priority_max() and sched_get_priority_min().

By default, the process priority and scheduling algorithm are inherited from or explicitly set by the parent process. Once running, the child process may change its priority by using this function.

Returns:

0

Success

-1

An error occurred (errno is set).

Errors:

EFAULT

A fault occurred trying to access the buffers provided.

EINVAL

The priority isn't a valid priority.

EPERM

The calling process doesn't have sufficient privilege to set the priority.

ESRCH

The process pid doesn't exist.

Classification:

POSIX 1003.1 PS

Caveats:

Currently, the implementation of sched_setparam() isn't 100% POSIX 1003.1-1996. The sched_setparam() function sets the scheduling parameters for thread 1 in the process pid, or for the calling thread if pid is 0.

If you depend on this in new code, it will not be portable. POSIX 1003.1 says sched_setparam() should return -1 and set errno to EPERM in a multithreaded application.

See also:

errno, getprio(), sched_getparam(), sched_get_priority_max(), sched_get_priority_min(), sched_getscheduler(), sched_param, sched_setscheduler(), sched_yield(), setprio()