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sysevent_subscribe_event, sysevent_unsubscribe_event - register or unregister interest in event receipt

cc [ flag.\|.\|. ] file.\|.\|. -lsysevent [ library.\|.\|. ]
#include <libsysevent.h>

int sysevent_subscribe_event(sysevent_handle_t *sysevent_hdl,
 char *event_class, char **event_subclass_list,
 int num_subclasses);

void sysevent_unsubscribe_event(sysevent_handle_t *sysevent_hdl,
 char *event_class);

event_class event_subclass_list num_subclasses sysevent_hdl

The sysevent_subscribe_event() function registers the caller's interest in event notifications belonging to the class event_class and the subclasses contained in event_subclass_list. The subscriber handle sysevent_hdl is updated with the new subscription and the calling process receives event notifications from the event handler specified in sysevent_bind_handle.

System events matching event_class and a subclass contained in event_subclass_list published after the caller returns from sysevent_subscribe_event() are guaranteed to be delivered to the calling process. Matching system events published and queued prior to a call to sysevent_subscribe_event() may be delivered to the process's event handler.

The num_subclasses argument provides the number of subclass string elements in event_subclass_list.

A caller can use the event class EC_ALL to subscribe to all event classes and subclasses. The event class EC_SUB_ALL can be used to subscribe to all subclasses within a given event class.

Subsequent calls to sysevent_subscribe_event() are allowed to add additional classes or subclasses. To remove an existing subscription, sysevent_unsubscribe_event() must be used to remove the subscription.

The sysevent_unsubscribe_event() function removes the subscription described by event_class for sysevent_hdl. Event notifications matching event_class will not be delivered to the calling process upon return.

A caller can use the event class EC_ALL to remove all subscriptions for sysevent_hdl.

The library manages all subscription resources.

The sysevent_subscribe_event() function returns 0 if the subscription is successful. Otherwise, -1 is returned and errno is set to indicate the error.

The sysevent_unsubscribe_event() function returns no value.

The sysevent_subscribe_event() function will fail if: EACCES

EINVAL ENOMEM

Example 1 Subscribing for environmental events

#include <libsysevent.h>
#include <sys/nvpair.h>

static int32_t attr_int32;

#define CLASS1 "class1"
#define CLASS2 "class2"
#define SUBCLASS_1 "subclass_1"
#define SUBCLASS_2 "subclass_2"
#define SUBCLASS_3 "subclass_3"
#define MAX_SUBCLASS 3

static void
event_handler(sysevent_t *ev)
{
 nvlist_t *nvlist;

 /*
 * Special processing for events (CLASS1, SUBCLASS_1) and
 * (CLASS2, SUBCLASS_3)
 */
 if ((strcmp(CLASS1, sysevent_get_class_name(ev)) == 0 &&
 strcmp(SUBCLASS_1, sysevent_get_subclass_name(ev)) == 0) ||
 (strcmp(CLASS2, sysevent_get_subclass_name(ev) == 0) &&
 strcmp(SUBCLASS_3, sysevent_get_subclass(ev)) == 0)) {
 if (sysevent_get_attr_list(ev, &nvlist) != 0)
 return;
 if (nvlist_lookup_int32(nvlist, "my_int32_attr", &attr_int32)
 != 0)
 return;

 /* Event Processing */
 } else {
 /* Event Processing */
 }

}


int
main(int argc, char **argv)
{
 sysevent_handle_t *shp;
 const char *subclass_list[MAX_SUBCLASS];

 /* Bind event handler and create subscriber handle */
 shp = sysevent_bind_handle(event_handler);
 if (shp == NULL)
 exit(1);

 /* Subscribe to all CLASS1 event notifications */
 subclass_list[0] = EC_SUB_ALL;
 if (sysevent_subscribe_event(shp, CLASS1, subclass_list, 1) != 0) {
 sysevent_unbind_handle(shp);
 exit(1);
 }

 /* Subscribe to CLASS2 events for subclasses: SUBCLASS_1,
 * SUBCLASS_2 and SUBCLASS_3
 */
 subclass_list[0] = SUBCLASS_1;
 subclass_list[1] = SUBCLASS_2;
 subclass_list[2] = SUBCLASS_3;
 if (sysevent_subscribe_event(shp, CLASS2, subclass_list,
 MAX_SUBCLASS) != 0) {
 sysevent_unbind_handle(shp);
 exit(1);
 }

 for (;;) {
 (void) pause();
 }
}

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE

Interface Stability Committed

MT-Level MT-Safe

sysevent_bind_handle (3SYSEVENT), sysevent_get_attr_list (3SYSEVENT), sysevent_get_class_name (3SYSEVENT), sysevent_get_vendor_name (3SYSEVENT), attributes (7), syseventd (8)

The libsysevent interfaces do not work at all in non-global zones.