MirOS Manual: getpriority(2), setpriority(2)

GETPRIORITY(2)             BSD Programmer's Manual              GETPRIORITY(2)


     getpriority, setpriority - get/set program scheduling priority


     #include <sys/time.h>
     #include <sys/resource.h>

     getpriority(int which, id_t who);

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


     The scheduling priority of the process, process group, or user, as indi-
     cated by which and who is obtained with the getpriority() call and set
     with the setpriority() call. which is one of PRIO_PROCESS, PRIO_PGRP, or
     PRIO_USER, and who is interpreted relative to which (a process identifier
     for PRIO_PROCESS, process group identifier for PRIO_PGRP, and a user ID
     for PRIO_USER). A zero value of who denotes the current process, process
     group, or user. prio is a value in the range -20 to 20. The default
     priority is 0; lower priorities cause more favorable scheduling.

     The getpriority() call returns the highest priority (lowest numerical
     value) enjoyed by any of the specified processes. The setpriority() call
     sets the priorities of all of the specified processes to the specified
     value. Priority values outside the range -20 to 20 are truncated to the
     appropriate limit. Only the superuser may lower priorities.


     Since getpriority() can legitimately return the value -1, it is necessary
     to clear the external variable errno prior to the call, then check it
     afterward to determine if a -1 is an error or a legitimate value. The
     setpriority() call returns 0 if there is no error, or -1 if there is.


     getpriority() and setpriority() will fail if:

     [ESRCH]       No process was located using the which and who values

     [EINVAL]      which was not one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER.

     In addition to the errors indicated above, setpriority() will fail if:

     [EPERM]       A process was located, but neither its effective nor real
                   user ID matched the effective user ID of the caller.

     [EACCES]      A non-superuser attempted to lower a process priority.


     nice(1), fork(2), renice(8)


     The getpriority() function call appeared in 4.2BSD.

MirOS BSD #10-current            June 4, 1993                                1

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