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sigevent(7) [bsd man page]

SIGEVENT(7)						     Linux Programmer's Manual						       SIGEVENT(7)

NAME
sigevent - structure for notification from asynchronous routines SYNOPSIS
#include <signal.h> union sigval { /* Data passed with notification */ int sival_int; /* Integer value */ void *sival_ptr; /* Pointer value */ }; struct sigevent { int sigev_notify; /* Notification method */ int sigev_signo; /* Notification signal */ union sigval sigev_value; /* Data passed with notification */ void (*sigev_notify_function) (union sigval); /* Function used for thread notification (SIGEV_THREAD) */ void *sigev_notify_attributes; /* Attributes for notification thread (SIGEV_THREAD) */ pid_t sigev_notify_thread_id; /* ID of thread to signal (SIGEV_THREAD_ID) */ }; DESCRIPTION
The sigevent structure is used by various APIs to describe the way a process is to be notified about an event (e.g., completion of an asyn- chronous request, expiration of a timer, or the arrival of a message). The definition shown in the SYNOPSIS is approximate: some of the fields in the sigevent structure may be defined as part of a union. Pro- grams should employ only those fields relevant to the value specified in sigev_notify. The sigev_notify field specifies how notification is to be performed. This field can have one of the following values: SIGEV_NONE A "null" notification: don't do anything when the event occurs. SIGEV_SIGNAL Notify the process by sending the signal specified in sigev_signo. If the signal is caught with a signal handler that was registered using the sigaction(2) SA_SIGINFO flag, then the following fields are set in the siginfo_t structure that is passed as the second argument of the handler: si_code This field is set to a value that depends on the API delivering the notification. si_signo This field is set to the signal number (i.e., the same value as in sigev_signo). si_value This field is set to the value specified in sigev_value. Depending on the API, other fields may also be set in the siginfo_t structure. The same information is also available if the signal is accepted using sigwaitinfo(2). SIGEV_THREAD Notify the process by invoking sigev_notify_function "as if" it were the start function of a new thread. (Among the implementation possibilities here are that each timer notification could result in the creation of a new thread, or that a single thread is cre- ated to receive all notifications.) The function is invoked with sigev_value as its sole argument. If sigev_notify_attributes is not NULL, it should point to a pthread_attr_t structure that defines attributes for the new thread (see pthread_attr_init(3)). SIGEV_THREAD_ID (Linux-specific) Currently used only by POSIX timers; see timer_create(2). SEE ALSO
timer_create(2), aio_fsync(3), aio_read(3), aio_write(3), getaddrinfo_a(3), lio_listio(3), mq_notify(3), aio(7), pthreads(7) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU
2017-07-13 SIGEVENT(7)

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SIGEVENT(7)						     Linux Programmer's Manual						       SIGEVENT(7)

NAME
sigevent - structure for notification from asynchronous routines SYNOPSIS
#include <signal.h> union sigval { /* Data passed with notification */ int sival_int; /* Integer value */ void *sival_ptr; /* Pointer value */ }; struct sigevent { int sigev_notify; /* Notification method */ int sigev_signo; /* Notification signal */ union sigval sigev_value; /* Data passed with notification */ void (*sigev_notify_function) (union sigval); /* Function used for thread notification (SIGEV_THREAD) */ void *sigev_notify_attributes; /* Attributes for notification thread (SIGEV_THREAD) */ pid_t sigev_notify_thread_id; /* ID of thread to signal (SIGEV_THREAD_ID) */ }; DESCRIPTION
The sigevent structure is used by various APIs to describe the way a process is to be notified about an event (e.g., completion of an asyn- chronous request, expiration of a timer, or the arrival of a message). The definition shown in the SYNOPSIS is approximate: some of the fields in the sigevent structure may be defined as part of a union. Pro- grams should employ only those fields relevant to the value specified in sigev_notify. The sigev_notify field specifies how notification is to be performed. This field can have one of the following values: SIGEV_NONE A "null" notification: don't do anything when the event occurs. SIGEV_SIGNAL Notify the process by sending the signal specified in sigev_signo. If the signal is caught with a signal handler that was registered using the sigaction(2) SA_SIGINFO flag, then the following fields are set in the siginfo_t structure that is passed as the second argument of the handler: si_code This field is set to a value that depends on the API delivering the notification. si_signo This field is set to the signal number (i.e., the same value as in sigev_signo). si_value This field is set to the value specified in sigev_value. Depending on the API, other fields may also be set in the siginfo_t structure. The same information is also available if the signal is accepted using sigwaitinfo(2). SIGEV_THREAD Notify the process by invoking sigev_notify_function "as if" it were the start function of a new thread. (Among the implementation possibilities here are that each timer notification could result in the creation of a new thread, or that a single thread is cre- ated to receive all notifications.) The function is invoked with sigev_value as its sole argument. If sigev_notify_attributes is not NULL, it should point to a pthread_attr_t structure that defines attributes for the new thread (see pthread_attr_init(3)). SIGEV_THREAD_ID (Linux-specific) Currently used only by POSIX timers; see timer_create(2). SEE ALSO
timer_create(2), aio_fsync(3), aio_read(3), aio_write(3), getaddrinfo_a(3), lio_listio(3), mq_notify(3), aio(7), pthreads(7) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU
2017-07-13 SIGEVENT(7)

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