NAME

       sched_setscheduler, sched_getscheduler — set/get scheduling policy and scheduler parameters

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <sched.h>

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

       int
       sched_getscheduler(pid_t pid);

DESCRIPTION

       The  sched_setscheduler() system call sets the scheduling policy and scheduling parameters of the process
       specified by pid to policy and the parameters specified in the sched_param structure pointed to by param,
       respectively.  The value of the sched_priority member in the param structure must be any  integer  within
       the inclusive priority range for the scheduling policy specified by policy.

       In this implementation, if the value of pid is negative the system call will fail.

       If a process specified by pid exists and if the calling process has permission, the scheduling policy and
       scheduling parameters will be set for the process whose process ID is equal to pid.

       If pid is zero, the scheduling policy and scheduling parameters are set for the calling process.

       In  this  implementation,  the  policy  of when a process can affect the scheduling parameters of another
       process is specified in IEEE Std 1003.1b-1993 (“POSIX.1”) as a write-style operation.

       The scheduling policies are in <sched.h>:

       [SCHED_FIFO]   First-in-first-out fixed priority scheduling with no round robin scheduling;

       [SCHED_OTHER]  The standard time sharing scheduler;

       [SCHED_RR]     Round-robin scheduling across same priority processes.

       The sched_param structure is defined in <sched.h>:

             struct sched_param {
                     int sched_priority;     /* scheduling priority */
             };

       The sched_getscheduler() system call returns the scheduling policy of the process specified by pid.

       If a process specified by pid exists and if the calling process has permission, the scheduling parameters
       for the process whose process ID is equal to pid are returned.

       In this implementation, the policy of when a process can obtain  the  scheduling  parameters  of  another
       process are detailed in IEEE Std 1003.1b-1993 (“POSIX.1”) as a read-style operation.

       If  pid  is  zero,  the  scheduling  parameters  for  the  calling  process  will  be  returned.  In this
       implementation, the sched_getscheduler system call will fail if pid is negative.

RETURN VALUES

       Upon successful completion, the value 0 is returned; otherwise the value -1 is returned  and  the  global
       variable errno is set to indicate the error.

ERRORS

       On failure errno will be set to the corresponding value:

       [ENOSYS]           The system is not configured to support this functionality.

       [EPERM]            The  requesting process doesn not have permission as detailed in IEEE Std 1003.1b-1993
                          (“POSIX.1”).

       [ESRCH]            No process can be found corresponding to that specified by pid.

       [EINVAL]           The value of the policy argument  is  invalid,  or  one  or  more  of  the  parameters
                          contained in param is outside the valid range for the specified scheduling policy.

SEE ALSO

       sched_get_priority_max(2),    sched_get_priority_min(2),   sched_getparam(2),   sched_rr_get_interval(2),
       sched_setparam(2), sched_yield(2)

STANDARDS

       The  sched_setscheduler()  and  sched_getscheduler()  system  calls  conform  to  IEEE  Std  1003.1b-1993
       (“POSIX.1”).

Debian                                           March 12, 1998                            SCHED_SETSCHEDULER(2)