getpriority(3C)                                            Standard C Library Functions                                            getpriority(3C)

NAME

       getpriority, setpriority - get or set process scheduling priority

SYNOPSIS

       #include <sys/resource.h>

       int getpriority(int which, id_t who);

       int setpriority(int which, id_t who, int priority);

DESCRIPTION

       The  getpriority()  function obtains the current scheduling priority of a process, process group, or user.  The setpriority() function sets
       the scheduling priority of a process, process group, or user.

       Target processes are specified by the values of the which and who arguments.  The which argument  can  be  one  of  the  following  values:
       PRIO_PROCESS,  PRIO_PGRP,  PRIO_USER,  PRIO_GROUP, PRIO_SESSION, PRIO_LWP, PRIO_TASK, PRIO_PROJECT, PRIO_ZONE, or PRIO_CONTRACT, indicating
       that the who argument is to be interpreted as a process ID, a process group ID, an effective user ID, an effective group ID, a session  ID,
       an  lwp  ID, a task ID, a project ID, a zone ID, or a process contract ID, respectively.  A 0 value for the who argument specifies the cur-
       rent process, process group, or user. A 0 value for the who argument is treated as valid group ID, session ID, lwp ID, task ID, project ID,
       zone ID, or process contract ID. A P_MYID value for the who argument can be used to specify the current group, session, lwp, task, project,
       zone, or process contract, respectively.

       If more than one process is specified, getpriority() returns the highest priority (lowest numerical value) pertaining to any of the  speci-
       fied processes, and setpriority() sets the priorities of all of the specified processes to the specified value.

       The  default  priority  is  0; negative priorities cause more favorable scheduling. The range of valid priority values is [-20, 20]. If the
       value specified to setpriority() is less than the system's lowest supported priority value, the system's lowest supported value is used. If
       it is greater than the system's highest supported value, the system's highest supported value is used.

       Only a process with appropriate privileges can raise its priority (that is, assign a lower numerical priority value).

       Any  processes or threads using SCHED_FIFO or SCHED_RR is unaffected by a call to setpriority(). This is not considered an error. A process
       that subsequently reverts to SCHED_OTHER need not have its priority affected by such a setpriority() call.

RETURN VALUES

       Upon successful completion, getpriority() returns an integer in the range from -20 to 20.  Otherwise, -1 is returned and errno  is  set  to
       indicate the error.

       Upon successful completion, setpriority() returns 0. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

       The getpriority() and setpriority() functions will fail if:

       ESRCH           No process could be located using the which and who argument values specified.

       EINVAL          The  value  of  the  which argument was not recognized, or the value of the who argument is not a valid process ID, process
                       group ID, user ID, group ID, session ID, lwp ID, task ID, project ID, or zone ID.

       In addition, setpriority() may fail if:

       EPERM           A process was located, but neither the real nor effective user ID of the executing process is the privileged user or  match
                       the effective user ID of the process whose priority is being changed.

       EACCES          A  request was made to change the priority to a lower numeric value (that is, to a higher priority) and the current process
                       does not have appropriate privileges.

EXAMPLES

       Example 1: Example using getpriority()

       The following example returns the current scheduling priority for the process ID returned by the call to getpid(2).

       #include <sys/resource.h>
       ...
       int which = PRIO_PROCESS;
       id_t pid;
       int ret;

       pid = getpid();
       ret = getpriority(which, pid);

       Example 2: Example using setpriority()

       The following example sets the priority for the current process ID to -20.

       #include <sys/resource.h>
       ...
       int which = PRIO_PROCESS;
       id_t pid;
       int priority = -20;
       int ret;

       pid = getpid();
       ret = setpriority(which, pid, priority);

USAGE

       The effect of changing the scheduling priority can vary depending on the process-scheduling algorithm in effect.

       Because getpriority() can return -1 on successful completion, it is necessary to set errno to 0 prior to a call to getpriority().  If  get-
       priority() returns -1, then errno can be checked to see if an error occurred or if the value is a legitimate priority.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Interface Stability          |Standard                     |
       +-----------------------------+-----------------------------+

SEE ALSO

       nice(1), renice(1), fork(2), sched_get_priority_max(3RT), sched_setscheduler(3RT), attributes(5), standards(5)

SunOS 5.10                                                          19 Jul 2004                                                    getpriority(3C)