jammy (2) timer_create.2freebsd.gz

NAME

     timer_create — create a per-process timer (REALTIME)

LIBRARY

     POSIX Real-time Library (librt, -lrt)

SYNOPSIS

     #include <time.h>
     #include <signal.h>

     int
     timer_create(clockid_t clockid, struct sigevent *restrict evp, timer_t *restrict timerid);

DESCRIPTION

     The timer_create() system call creates a per-process timer using the specified clock, clock_id, as the
     timing base.  The timer_create() system call returns, in the location referenced by timerid, a timer ID of
     type timer_t used to identify the timer in timer requests.  This timer ID is unique within the calling
     process until the timer is deleted.  The particular clock, clock_id, is defined in <time.h>.  The timer
     whose ID is returned is in a disarmed state upon return from timer_create().

     The evp argument, if non-NULL, points to a sigevent structure.  This structure, allocated by the
     application, defines the asynchronous notification to occur when the timer expires.

     If evp->sigev_notify is SIGEV_SIGNO or SIGEV_THREAD_ID, the signal specified in evp->sigev_signo will be
     sent to the calling process (SIGEV_SIGNO) or to the thread whose LWP ID is evp->sigev_notify_thread_id
     (SIGEV_THREAD_ID).  The information for the queued signal will include:

     Member      Value
     si_code     SI_TIMER
     si_value    the value stored in evp->sigev_value
     si_timerid  timer ID
     si_overrun  timer overrun count
     si_errno    If timer overrun is {DELAYTIMER_MAX}, an error code defined in <errno.h>

     If the evp argument is NULL, the effect is as if the evp argument pointed to a sigevent structure with the
     sigev_notify member having the value SIGEV_SIGNAL, the sigev_signo having a default signal number
     (SIGALRM), and the sigev_value member having the value of the timer ID.

     This implementation supports a clock_id of CLOCK_REALTIME or CLOCK_MONOTONIC.

     If evp->sigev_notify is SIGEV_THREAD and sev->sigev_notify_attributes is not NULL, if the attribute pointed
     to by sev->sigev_notify_attributes has a thread stack address specified by a call to
     pthread_attr_setstack() or pthread_attr_setstackaddr(), the results are unspecified if the signal is
     generated more than once.

RETURN VALUES

     If the call succeeds, timer_create() returns zero and updates the location referenced by timerid to a
     timer_t, which can be passed to the per-process timer calls.  If an error occurs, the system call returns a
     value of -1 and the global variable errno is set to indicate the error.  The value of timerid is undefined
     if an error occurs.

ERRORS

     The timer_create() system call will fail if:

     [EAGAIN]           The calling process has already created all of the timers it is allowed by this
                        implementation.

     [EINVAL]           The specified clock ID is not supported.

     [EINVAL]           The specified asynchronous notification method is not supported.

     [EFAULT]           Any arguments point outside the allocated address space or there is a memory protection
                        fault.

SEE ALSO

     clock_getres(2), timer_delete(2), timer_getoverrun(2), sigevent(3), siginfo(3)

STANDARDS

     The timer_create() system call conforms to IEEE Std 1003.1-2004 (“POSIX.1”).

HISTORY

     Support for POSIX per-process timer first appeared in FreeBSD 7.0.