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#include <signal.h> #include <time.h> int timer_create(clockid_t clock_id, struct sigevent *restrict evp, timer_t *restrict timerid);
The evp argument, if non-null, points to a sigevent structure. This structure, allocated by the application, defines the asynchronous notification that will occur when the timer expires (see signal.h(3HEAD) for event notification details). 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 the value SIGALRM, and the sigev_value member having the value of the timer ID.
The system defines a set of clocks that can be used as timing bases for per-process timers. The following values for clock_id are supported: CLOCK_REALTIME
wall clock
user CPU usage clock
user and system CPU usage clock
non-adjustable, high-resolution clock
For timers created with a clock_id of CLOCK_HIGHRES, the system will attempt to use an optimal hardware source. This may include, but is not limited to, per-CPU timer sources. The actual hardware source used is transparent to the user and may change over the lifetime of the timer. For example, if the caller that created the timer were to change its processor binding or its processor set, the system may elect to drive the timer with a hardware source that better reflects the new binding. Timers based on a clock_id of CLOCK_HIGHRES are ideally suited for interval timers that have minimal jitter tolerance.
Timers are not inherited by a child process across a fork(2) and are disarmed and deleted by a call to one of the exec functions (see exec(2)).
The system lacks sufficient signal queuing resources to honor the request, or the calling process has already created all of the timers it is allowed by the system.
The specified clock ID, clock_id, is not defined.
ATTRIBUTE TYPE ATTRIBUTE VALUE |
Interface Stability Committed |
MT-Level MT-Safe with exceptions |
Standard See standards(5). |