As mentioned previously, we use the timer_settime(2) system call to either arm (start) or disarm (stop) a timer:
#include <time.h>int timer_settime(timer_t timerid, int flags, const struct itimerspec *new_value, struct itimerspec *old_value);Link with -lrt.
As one can have multiple concurrent POSIX timers running simultaneously, thus we need to specify exactly which timer we are referring to; this is done via the first parameter timer_id, which is the timer's ID, and the effective return of the previously seen timer_create(2) system call.
The important data structure employed here is the itimerspec; its definition is as follows:
struct timespec { time_t tv_sec; /* Seconds */ long tv_nsec; ...
