setitimer

Arms or disarms one of the per-process interval timers.

Prototype

int setitimer(u_int which, struct itimerval *itv, struct itimerval *oitv);

Returns: int

Arguments

Name	Type	Dir
which	u_int	-
itv	struct itimerval	-
oitv	struct itimerval	-

Version history

XNU tag	macOS	#
xnu-1456.1.26	macOS 10.6 Snow Leopard	83
xnu-1699.24.8	macOS 10.7 Lion	83
xnu-2050.18.24	macOS 10.8 Mountain Lion	83
xnu-2422.115.4	macOS 10.9 Mavericks	83
xnu-2782.40.9	macOS 10.10 Yosemite	83
xnu-3247.1.106	macOS 10.11 El Capitan	83
xnu-3789.1.32	macOS 10.12 Sierra	83
xnu-4570.1.46	macOS 10.13 High Sierra	83
xnu-4903.221.2	macOS 10.14 Mojave	83
xnu-6153.11.26	macOS 10.15 Catalina	83
xnu-7195.50.7.100.1	macOS 11.0 Big Sur	83
xnu-8019.41.5	macOS 12.0 Monterey	83
xnu-8792.41.9	macOS 13.0 Ventura	83
xnu-10002.1.13	macOS 14.0 Sonoma	83
xnu-11215.1.10	macOS 15.0 Sequoia	83
xnu-11417.101.15	macOS 15.4 Sequoia	83
xnu-12377.1.9	macOS 26.0 Tahoe	83
xnu-10002.41.9	—	83
xnu-10002.61.3	—	83
xnu-10002.81.5	—	83
xnu-10063.101.15	—	83
xnu-10063.121.3	—	83
xnu-10063.141.1	—	83
xnu-11215.41.3	—	83
xnu-11215.61.5	—	83
xnu-11215.81.4	—	83
xnu-11417.121.6	—	83
xnu-11417.140.69	—	83
xnu-12377.101.15	—	83
xnu-12377.41.6	—	83
xnu-12377.61.12	—	83
xnu-12377.81.4	—	83
xnu-1486.2.11	—	83
xnu-1504.15.3	—	83
xnu-1504.3.12	—	83
xnu-1504.7.4	—	83
xnu-1504.9.17	—	83
xnu-1504.9.26	—	83
xnu-1504.9.37	—	83
xnu-1699.22.73	—	83
xnu-1699.22.81	—	83
xnu-1699.24.23	—	83
xnu-1699.26.8	—	83
xnu-1699.32.7	—	83
xnu-2050.22.13	—	83
xnu-2050.24.15	—	83
xnu-2050.48.11	—	83
xnu-2050.7.9	—	83
xnu-2050.9.2	—	83
xnu-2422.1.72	—	83
xnu-2422.100.13	—	83
xnu-2422.110.17	—	83
xnu-2422.90.20	—	83
xnu-2782.1.97	—	83
xnu-2782.10.72	—	83
xnu-2782.20.48	—	83
xnu-2782.30.5	—	83
xnu-3247.10.11	—	83
xnu-3248.20.55	—	83
xnu-3248.30.4	—	83
xnu-3248.40.184	—	83
xnu-3248.50.21	—	83
xnu-3248.60.10	—	83
xnu-3789.21.4	—	83
xnu-3789.31.2	—	83
xnu-3789.41.3	—	83
xnu-3789.51.2	—	83
xnu-3789.60.24	—	83
xnu-3789.70.16	—	83
xnu-4570.20.62	—	83
xnu-4570.31.3	—	83
xnu-4570.41.2	—	83
xnu-4570.51.1	—	83
xnu-4570.61.1	—	83
xnu-4570.71.2	—	83
xnu-4903.231.4	—	83
xnu-4903.241.1	—	83
xnu-4903.270.47	—	83
xnu-6153.101.6	—	83
xnu-6153.121.1	—	83
xnu-6153.141.1	—	83
xnu-6153.41.3	—	83
xnu-6153.61.1	—	83
xnu-6153.81.5	—	83
xnu-7195.101.1	—	83
xnu-7195.121.3	—	83
xnu-7195.141.2	—	83
xnu-7195.60.75	—	83
xnu-7195.81.3	—	83
xnu-8019.61.5	—	83
xnu-8019.80.24	—	83
xnu-8020.101.4	—	83
xnu-8020.121.3	—	83
xnu-8020.140.41	—	83
xnu-8792.61.2	—	83
xnu-8792.81.2	—	83
xnu-8796.101.5	—	83
xnu-8796.121.2	—	83
xnu-8796.141.3	—	83

Examples

Fire SIGALRM every 500ms

#include <sys/time.h>

struct itimerval it = {
    .it_interval = { .tv_sec = 0, .tv_usec = 500000 },
    .it_value    = { .tv_sec = 0, .tv_usec = 500000 },
};
setitimer(ITIMER_REAL, &it, NULL);

Notes

Setting it_value to zero disarms the timer; setting it_interval to non-zero requests periodic firing. Signal delivery is best-effort and can be coalesced if the process cannot run handlers fast enough. Note that only one timer per kind exists per process, so libraries that quietly install one will collide with application code.

Related APIs

getitimersigactionsigsuspendgettimeofdaykill