Manual browser: timer_settime(2)



timer_settime, timer_gettime, timer_getoverrunprocess timer manipulation


Standard C Library (libc, -lc)


#include <time.h>

timer_settime(timer_t timerid, int flags, const struct itimerspec * restrict tim, struct itimerspec * restrict otim);

timer_gettime(timer_t timerid, struct itimerspec *tim);

timer_getoverrun(timer_t timerid);


The timer_settime() sets the next expiration time of the timer with ID timerid to the it_value (see itimerspec(3)) specified in the tim argument. If the value is 0, the timer is disarmed. If the argument otim is not NULL the old timer settings are returned.

If the flags argument is set to TIMER_RELTIME then the expiration time is set to the value in nanoseconds specified in the tim argument from the time the call to timer_settime() was made. If the flags argument is set to TIMER_ABSTIME then the expiration time is set to be equal to the difference between the clock associated with this timer, and the value specified in the tim argument. If that time has already passed, then the call succeeds, and the expiration notification occurs.

If the it_interval of the tim argument is non-zero, then the timer reloads upon expiration.

The timer_gettime() function returns the current settings of the timer specified by the timerid argument in the tim argument.

Only one notification event (signal) can be pending for a given timer and process. If a timer expires while the signal is still queued for delivery, then the overrun counter for that timer is increased. The counter can store values up to DELAYTIMER_MAX. When the signal is finally delivered to the process, then the timer_getoverrun() function can be used to retrieve the overrun counter for the timer specified in the timerid argument.


Expiration time values are always rounded up to the resolution of the timer, so a notification will never be sent before the requested time. Values returned in the otim argument of timer_settime() or in the tim argument of timer_gettime() are subject to the above rounding effect and might not exactly match the requested values by the user.


If successful, the timer_gettime() and timer_settime() functions return 0, and the timer_getoverrun() function returns the expiration overrun count for the specified timer. Otherwise, the functions return -1, and set errno to indicate the error.


The timer_gettime(), timer_getoverrun(), and timer_settime() functions will fail if:
The argument timerid does not correspond to a valid timer id as returned by timer_create() or that timer id has been deleted by timer_delete().

The timer_settime() function will fail if:

A nanosecond field in the tim structure specified a value less than zero or greater than or equal to 10e9.


IEEE Std 1003.1b-1993 (“POSIX.1b”), IEEE Std 1003.1i-1995 (“POSIX.1i”)
May 17, 2010 NetBSD 7.0