sched_get_priority_max(S)

sched_get_priority_max, sched_get_priority_min -- get the maximum/minimum priority

Syntax

cc . . . -lc

#include <sched.h>

int sched_get_priority_max(int policy);

int sched_get_priority_min(int policy);

Description

sched_get_priority_max- get the maximum priority

sched_get_priority_min- get the minimum priority

sched_get_priority_max and sched_get_priority_min return the maximum and minimum priorities allocated to the scheduling policy specified by policy.

The following policies are available:

SCHED_FIFO: first in first out. Processes are allowed on the CPU in the order in which they were added to the queue of processes to be run, for each priority.
SCHED_RR: round-robin. Identical to SCHED_FIFO except that a process runs only for a set time slice (see sched_rr_get_interval(S)). Once the process has completed its time slice it is placed on the tail of the queue of processes to be run, for its priority.
SCHED_OTHER: non-realtime scheduling. This uses the traditional UNIX scheduler.

Return values

Upon successful completion sched_get_priority_max and sched_get_priority_min return the maximum and minimum priorities respectively. If an error has occurred both functions return -1, and errno is set to indicate the error.

Diagnostics

If sched_get_priority_max or sched_get_priority_min terminate due to an error, they will set errno to one of the following values:

[EINVAL]: The specified policy does not exist.
[ENOSYS]: The functions are not supported.

Examples

The following example illustrates the use of sched_get_priority_max and sched_get_priority_min:

   int pmin, pmax, priority = 36;
   struct sched_param sp;
   ...
   pmin = sched_get_priority_min(SCHED_FIFO);
   pmax = sched_get_priority_max(SCHED_FIFO);
   
   if (priority >= pmin && priority <= pmax) {
      sp.sched_priority = priority;
   }
   else {
      sp.sched_priority = pmin;
   }
   

   sched_setparam(0, &sp);

Files

/usr/lib/libc.a: linking library

Standards conformance

Text reprinted and/or adapted from IEEE Std 1003.1b-1993, IEEE Standard for Information Technology, POSIX Part 1: System Application Program Interface (API) Amendment 1: Realtime Extensions [C Language], copyright © 1993 by the Institute of Electrical and Electronics Engineers, Inc. The IEEE takes no responsibility for and will assume no liability for damages resulting from the reader's misinterpretation of said information resulting from the placement and context in this publication. Information is reproduced with the permission of the IEEE.