GETPRIORITY(2)                       BSD                        GETPRIORITY(2)



NAME
     getpriority, setpriority - get/set program scheduling priority

SYNOPSIS
     #include <sys/resource.h>

     prio = getpriority(which, who)
     int prio, which, who;

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

DESCRIPTION
     The scheduling priority of the process, process group, or user, as
     indicated 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.  who is interpreted relative to which:  a process identifier
     for PRIO_PROCESS, a process group identifier for PRIO_PGRP, and a user ID
     for PRIO_USER.  A 0 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.  Only the super-user can lower priorities.

ERRORS
     getpriority and setpriority may return one of the following errors:

     [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 to the errors indicated above, setpriority may fail with one
     of the following errors returned:

     [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.

NOTES
     Domain/OS BSD does not require you to be the super-user or to own a
     process to lower its priority.

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

DIAGNOSTICS
     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.