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GETPRIORITY(2)              BSD System Calls Manual             GETPRIORITY(2)

NAME
     getpriority, setpriority -- get/set process scheduling priority

SYNOPSIS
     #include <&lt;sys/resource.h>&gt;

     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.  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.

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:

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

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

     In addition, 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.

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

STANDARDS
     The getpriority() and setpriority() functions conform to IEEE Std
     1003.1-2008 (``POSIX.1'').

HISTORY
     The predecessor of these functions, the former nice() system call,
     appeared in Version 3 AT&T UNIX and was removed in 4.3BSD-Reno.  The
     getpriority() and setpriority() system calls appeared in 4.1cBSD.

BSD                             April 28, 2017                             BSD