SIGEVENT(3)

NAME
sigevent - asynchronous event notification

SYNOPSIS
#include <signal.h>

DESCRIPTION
Some operations permit threads to request asynchronous notification of events via a struct sigevent structure. This structure contains several fields that describe the requested notification:
Type | Member | Description
int | sigev_notify | notification method
int | sigev_signo | signal number
union sigval | sigev_value | signal value
int | sigev_notify_kqueue |
kqueue(2) file descriptor
unsigned short | sigev_notify_kevent_flags | kevent flags
lwpid_t | sigev_notify_thread_id | LWP ID
void (*)(union sigval) | sigev_notify_function |
callback function pointer
pthread_attr_t * | sigev_notify_attributes |
callback thread attributes

The sigev_notify field specifies the notification method used when the event triggers:

SIGEV_NONE
    No notification is sent.

SIGEV_SIGNAL
    The signal sigev_signo is queued as a real-time signal to the calling process. The value stored in sigev_value will be present in the si_value of the siginfo_t structure of the queued signal.

SIGEV_THREAD
    The notification function in sigev_notify_function is called in a separate thread context. The thread is created with the attributes specified in *sigev_notify_attributes. The value stored in sigev_value is passed as the sole argument to sigev_notify_function. If sigev_notify_attributes is NULL, the thread is created with default attributes.

SIGEV_KEVENT
    A new kevent is posted to the kqueue sigev_notify_kqueue. The udata member of the kevent structure contains the value stored in sigev_value. The meaning of other fields in the kevent are specific to the type of triggered event.

SIGEV_THREAD_ID
    The signal sigev_signo is queued to the thread whose LWP ID is sigev_notify_thread_id. The value stored in sigev_value will be present in the si_value of the siginfo_t structure of the queued signal.

NOTES
Note that programs wishing to use SIGEV_THREAD notifications must link against the librt.

SEE ALSO
aio_read(2), mq_notify(2), timer_create(2), siginfo(3)

STANDARDS
The struct sigevent type conforms to p1003.1-2004.

HISTORY
The sigevent structure first appeared in FreeBSD 3.3.