Manual Pages  — SIGEVENT

sigevent – asynchronous event notification

SYNOPSIS DESCRIPTION NOTES SEE ALSO HISTORY STANDARDS

#include <signal.h>

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.

Note that programs wishing to use SIGEV_THREAD notifications must link against the POSIX Real\-time Library (librt, -lrt)

The sigevent structure first appeared in FreeBSD 3.3 .

The struct sigevent type conforms to IEEE Std 1003.1-2004 ("POSIX.1").