setpriority(2) - NetBSD Manual Pages

GETPRIORITY(2)            NetBSD System Calls Manual            GETPRIORITY(2)


NAME

     getpriority, setpriority -- get/set program scheduling priority


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/resource.h>

     int
     getpriority(int which, id_t who);

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


DESCRIPTION

     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.

     The priority is maintained in a per-process basis and affects scheduling
     of LWPs which belong to the process and use the SCHED_OTHER scheduling
     class.

     which is one of PRIO_PROCESS, PRIO_PGRP, or PRIO_USER, and who is inter-
     preted 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; numeri-
     cally lower priority values cause more favorable scheduling.  A value of
     19 or 20 will schedule a process only when nothing at priority <= 0 is
     runnable.

     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.  Only the super-user may lower priority values.


RETURN VALUES

     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.


ERRORS

     getpriority() and setpriority() will fail if:

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

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

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

     [EACCES]           A non super-user attempted to lower a process priority
                        value.

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


SEE ALSO

     nice(1), fork(2), sched(3), renice(8)


HISTORY

     The getpriority() function call appeared in 4.2BSD.

NetBSD 9.0                      April 13, 2012                      NetBSD 9.0