KFILTER_REGISTER(9)					   BSD Kernel Developer's Manual				       KFILTER_REGISTER(9)

NAME

     kfilter_register, kfilter_unregister -- add or remove kernel event filters

SYNOPSIS

     #include <sys/event.h>

     int
     kfilter_register(const char *name, struct filterops *filtops, int *retfilter);

     int
     kfilter_unregister(const char *name);

DESCRIPTION

     The kfilter_register() function adds a new kernel event filter (kfilter) to the system, for use by callers of kqueue(2) and kevent(2).  name
     is the name of the new filter (which must not already exist), and filtops is a pointer to a filterops structure which describes the filter
     operations.  Both name and filtops will be copied to an internal data structure, and a new filter number will be allocated.  If retfilter is
     not NULL, then the new filter number will be returned in the address pointed at by retfilter.

     The kfilter_unregister() function removes a kfilter named name that was previously registered with kfilter_register().  If a filter with the
     same name is later reregistered with kfilter_register(), it will get a different filter number (i.e., filter numbers are not recycled).  It
     is not possible to unregister the system filters (i.e., those that start with ``EVFILT_'' and are documented in kqueue(2)).

     The filterops structure is defined as follows:

	   struct filterops {
		   int	   f_isfd;	   /* true if ident == filedescriptor */
		   int	   (*f_attach)(struct knote *kn);
					   /* called when knote is ADDed */
		   void    (*f_detach)(struct knote *kn);
					   /* called when knote is DELETEd */
		   int	   (*f_event)(struct knote *kn, long hint);
					   /* called when event is triggered */
	   };

     If the filter operation is for a file descriptor, f_isfd should be non-zero, otherwise it should be zero.	This controls where the kqueue(2)
     system stores the knotes for an object.

RETURN VALUES

     kfilter_register() returns 0 on success, EINVAL if there's an invalid argument, or EEXIST if the filter already exists,

     kfilter_unregister() returns 0 on success, EINVAL if there's an invalid argument, or ENOENT if the filter doesn't exist.

SEE ALSO

     kqueue(2), free(9), knote(9), malloc(9)

HISTORY

     The kfilter_register() and kfilter_unregister() functions first appeared in NetBSD 2.0.

AUTHORS

     The kfilter_register() and kfilter_unregister() functions were implemented by Luke Mewburn <lukem@NetBSD.org>.

BSD
								 October 23, 2002							       BSD