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NAME
     timer_create - create a per-process timer (REALTIME)


LIBRARY
     library “librt”


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 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 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, and the sigev_value member
     having the value of the timer ID.

     The implementations 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.

     [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_getoverun(2), siginfo(3)


STANDARDS
     The timer_create() system call conforms to


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