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

NAME
     ggeettpprriioorriittyy, sseettpprriioorriittyy - get/set program scheduling priority

SYNOPSIS
     ##iinncclluuddee <>

     int
     ggeettpprriioorriittyy(int which, idt who);

     int
     sseettpprriioorriittyy(int which, idt 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 ggeettpprriioorriittyy() call and set
     with the sseettpprriioorriittyy() call.  Additionally, the current thread can be set
     to background state.  Which is one of PRIOPROCESS, PRIOPGRP, PRIOUSER,
     or PRIODARWINTHREAD, and who is interpreted relative to which (a
     process identifier for PRIOPROCESS, process group identifier for
     PRIOPGRP, and a user ID for PRIOUSER).  A zero value of who denotes the
     current process, process group, user, thread (for PRIODARWINTHREAD).
     prio is a value in the range -20 to 20.  The default priority is 0; lower
     priorities cause more favorable scheduling.  For PRIODARWINTHREAD, prio
     is either 0 (to remove current thread from background status) or
     PRIODARWINBG (to set current thread into background state).

     The ggeettpprriioorriittyy() call returns the highest priority (lowest numerical
     value) enjoyed by any of the specified processes or for PRIODAR-
     WINTHREAD returns 0 when current thread is not in background state or 1
     when the current thread is in background state.  The sseettpprriioorriittyy() call
     sets the priorities of all of the specified processes to the specified
     value.  When setting a thread into background state the scheduling prior-
     ity is set to lowest value, disk and network IO are throttled.  Network
     IO will be throttled for any sockets the thread opens after going into
     background state.  Any previously opened sockets are not affected.  Only
     the super-user may lower priorities, but any thread can set itself into
     background state.

RETURN VALUES
     Since ggeettpprriioorriittyy() 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
     sseettpprriioorriittyy() call returns 0 if there is no error, or -1 if there is.

EERRRROORRSS
     GGeettpprriioorriittyy() and sseettpprriioorriittyy() will fail if:

     [EINVAL]           Which is not one of PRIOPROCESS, PRIOPGRP,
                        PRIOUSER, or PRIODARWINTHREAD.

     [EINVAL]           Who is not a valid process, process group, or user ID.

     [EINVAL]           Who is not 0 when which is PRIODARWINTHREAD.

     [ESRCH]            No process can be located using the which and who val-
                        ues specified.

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

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

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

LEGACY SYNOPSIS
     ##iinncclluuddee <>
     ##iinncclluuddee <>

     The include file  is necessary.

     int
     ggeettpprriioorriittyy(int which, int who);

     int
     sseettpprriioorriittyy(int which, int who, int value);

     The type of who has changed.

SEE ALSO
     nice(1), fork(2), compat(5), renice(8)

HISTORY     The ggeettpprriioorriittyy() function call appeared in 4.2BSD.

4th Berkeley Distribution        June 4, 1993        4th Berkeley Distribution