Go to main content

man pages section 3: Extended Library Functions, Volume 4

Exit Print View

Updated: Thursday, June 13, 2019
 
 

sysevent_unsubscribe_event(3SYSEVENT)

Name

sysevent_subscribe_event, sysevent_unsubscribe_event - register or unregister interest in event receipt

Synopsis

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);

Parameters

event_class

system event class string

event_subclass_list

array of subclass strings

num_subclasses

number of subclass strings

sysevent_hdl

sysevent subscriber handle

Description

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.

Return Values

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.

Errors

The sysevent_subscribe_event() function will fail if:

EACCES

The calling process has an ID other than the privileged user.

EINVAL

The sysevent_hdl argument is an invalid sysevent handle.

ENOMEM

There is insufficient memory available to allocate subscription resources.

Examples

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();
    }
}

Attributes

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

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
MT-Safe

See Also

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

Notes

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