NAME    [Toc]    [Back]

     rtprio -- examine or modify a process realtime or idle priority

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <sys/types.h>
     #include <sys/rtprio.h>

     int
     rtprio(int function, pid_t pid, struct rtprio *rtp);

DESCRIPTION    [Toc]    [Back]

     The rtprio() system call is used to lookup or change the realtime or idle
     priority of a process.

     The function argument specifies the operation to be performed.
     RTP_LOOKUP to lookup the current priority, and RTP_SET to set the priority.
  The pid argument specifies the process to be used, 0 for the current
 process.

     The *rtp argument is a pointer to a struct rtprio which is used to specify
 the priority and priority type.  This structure has the following
     form:

     struct rtprio {
	     u_short type;
	     u_short prio;
     };

     The value of the type field may be RTP_PRIO_REALTIME for realtime priorities,
 RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle
     priorities.  The priority specified by the prio field ranges between 0
     and RTP_PRIO_MAX (usually 31).  0 is the highest possible priority.

     Realtime and idle priority is inherited through fork() and exec().

     A realtime process can only be preempted by a process of equal or higher
     priority, or by an interrupt; idle priority processes will run only when
     no other real/normal priority process is runnable.  Higher real/idle priority
 processes preempt lower real/idle priority processes.  Processes of
     equal real/idle priority are run round-robin.

RETURN VALUES    [Toc]    [Back]

     The rtprio() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS    [Toc]    [Back]

     The rtprio() system call will fail if

     [EINVAL]		The specified prio was out of range.

     [EPERM]		The calling process is not allowed to set the realtime
			priority.  Only root is allowed to change the realtime
			priority of any process, and non-root may only change
			the idle priority of the current process.

     [ESRCH]		The specified process was not found.

AUTHORS    [Toc]    [Back]

     The original author was Henrik Vestergaard Draboel <hvd@terry.ping.dk>.
     This implementation in FreeBSD was substantially rewritten by David
     Greenman.

SEE ALSO    [Toc]    [Back]

     nice(1), ps(1), rtprio(1), setpriority(2), nice(3), renice(8)


FreeBSD 5.2.1			 July 23, 1994			 FreeBSD 5.2.1