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 POSIX Real-time Library (librt, -lrt).

HISTORY

The sigevent structure first appeared in FreeBSD 3.3.

STANDARDS

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