定时器说明

•函数功能：通过文件I/O方式去获取定时器的通知事件
•相关API：
–int timerfd_create(int clockid, int flags);
–int timerfd_settime(int fd, int flags, const struct itimerspec *new_value,
struct itimerspec *old_value);
–int timerfd_gettime(int fd, sturct itimerspec *curr_value);

举例

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <stdint.h> #include <time.h> #include <sys/time.h> #include <sys/timerfd.h> #define handle_error(msg) \ do{perror(msg);exit(EXIT_FAILURE);}while(0) void print_time () { struct timeval tv; gettimeofday (&tv, NULL); printf ("current time: %ld.%ld\n", tv.tv_sec, tv.tv_usec); } int main (int argc, char *argv[]) { struct timespec now; if (clock_gettime (CLOCK_REALTIME, &now) == -1) handle_error ("clock_gettime"); struct itimerspec new_value; new_value.it_value.tv_sec = now.tv_sec + 10; // 10s later,timer will timeout new_value.it_value.tv_nsec = now.tv_nsec; new_value.it_interval.tv_sec = 3; //timer intelval new_value.it_interval.tv_nsec = 0; int fd = timerfd_create (CLOCK_REALTIME, 0); if (fd == -1) handle_error ("timerfd_creat"); if (timerfd_settime(fd, TFD_TIMER_ABSTIME, &new_value, NULL) == -1) handle_error ("timerfd_settime"); print_time (); printf ("timer started\n"); for (uint64_t tot_exp = 0; tot_exp < 20;) //timer run times: 20 { uint64_t exp; ssize_t s = read (fd, &exp, sizeof(uint64_t)); if (s != sizeof(uint64_t)) handle_error ("read"); tot_exp += exp; print_time (); printf ("read: %llu, total: %llu\n", exp, tot_exp); } return 0; }