linux新的API signalfd、timerfd、eventfd使用说明——timerfd
看一下timerfd的例子，上代码：
#include <sys/timerfd.h>#include <sys/time.h>#include <time.h>#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <stdint.h> /* Definition of uint64_t */#define handle_error(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)void printTime(){ struct timeval tv; gettimeofday(&tv, NULL); printf("printTime: current time:%ld.%ld ", 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 + atoi(argv[1]); new_value.it_value.tv_nsec = now.tv_nsec; new_value.it_interval.tv_sec = atoi(argv[2]); new_value.it_interval.tv_nsec = 0; int fd = timerfd_create(CLOCK_REALTIME, 0); if (fd == -1) handle_error("timerfd_create"); if (timerfd_settime(fd, TFD_TIMER_ABSTIME, &new_value, NULL) == -1) handle_error("timerfd_settime"); printTime(); printf("timer startedn"); for (uint64_t tot_exp = 0; tot_exp < atoi(argv[3]);) { uint64_t exp; ssize_t s = read(fd, &exp, sizeof(uint64_t)); if (s != sizeof(uint64_t)) handle_error("read"); tot_exp += exp; printTime(); printf("read: %llu; total=%llun",exp, tot_exp); } exit(EXIT_SUCCESS);}相关结构体如下：
struct timespec { time_t tv_sec; /* Seconds */ long tv_nsec; /* Nanoseconds */};struct itimerspec { struct timespec it_interval; /* Interval for periodic timer */ struct timespec it_value; /* Initial expiration */};代码L25-L29：初始化定时器的参数，初始间隔与定时间隔。
L32：创建定时器fd，CLOCK_REALTIME：真实时间类型，修改时钟会影响定时器；CLOCK_MONOTONIC：相对时间类型，修改时钟不影响定时器。
L35：设置定时器的值。
L44：阻塞等待定时器到期。返回值是未处理的到期次数。比如定时间隔为2秒，但过了10秒才去读取，则读取的值是5。
编译运行：编译时要加rt库(g++ -lrt timerfd.cc -o timerfd)
[root@localhost appTest]# ./timerfd 5 2 10
printTime: current time:1357391736.146196 timer started
printTime: current time:1357391741.153430 read: 1; total=1
printTime: current time:1357391743.146550 read: 1; total=2
printTime: current time:1357391745.151483 read: 1; total=3
printTime: current time:1357391747.161155 read: 1; total=4
printTime: current time:1357391749.153934 read: 1; total=5
printTime: current time:1357391751.157309 read: 1; total=6
printTime: current time:1357391753.158384 read: 1; total=7
printTime: current time:1357391755.150470 read: 1; total=8
printTime: current time:1357391757.150253 read: 1; total=9
printTime: current time:1357391759.149954 read: 1; total=10
[root@localhost appTest]#
第一个参数5为第一次定时器到期间隔，第二个参数2为定时器的间隔，第三个参数为定时器到期10次则退出。程序运行(5+2*10)S退出。
详细信息可以：man timerfd_create
