Sets a process scheduling priority to a constant value.
Standard C Library (libc.a)
The setpri subroutine sets the scheduling priority of all threads in a process to be a constant. All threads have their scheduling policies changed to SCHED_RR. A process nice value and CPU usage can no longer be used to determine a process scheduling priority. Only processes that have root user authority can set a process scheduling priority to a constant.
| Item | Description |
|---|---|
| ProcessID | Specifies the process ID. If this value is 0 then the current process scheduling priority is set to a constant. |
| Priority | Specifies the scheduling priority for the process. A lower number value designates a higher scheduling priority. The Priority parameter must be in the range PRIORITY_MIN < Priority < PRIORITY_MAX. (See the sys/sched.h file.) |
Upon successful completion, the setpri subroutine returns the former scheduling priority of the process just changed. Otherwise, a value of -1 is returned and the errno global variable is set to indicate the error.
The setpri subroutine is unsuccessful if one or more of the following is true:
| Item | Description |
|---|---|
| EINVAL | The priority specified by the Priority parameter is outside the range of acceptable priorities. |
| EPERM | The process executing the setpri subroutine call does not have root user authority. |
| ESRCH | No process can be found corresponding to that specified by the ProcessID parameter. |