linux下定时器的使用--timer_create等系列

#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

#define CLOCKID CLOCK_REALTIME

void timer_thread(union sigval v)
{
	printf("timer_thread function! %d\n", v.sival_int);
}

int main()
{
	// XXX int timer_create(clockid_t clockid, struct sigevent *evp, timer_t *timerid);
	// clockid--值：CLOCK_REALTIME,CLOCK_MONOTONIC，CLOCK_PROCESS_CPUTIME_ID,CLOCK_THREAD_CPUTIME_ID
	// evp--存放环境值的地址,结构成员说明了定时器到期的通知方式和处理方式等
	// timerid--定时器标识符
	timer_t timerid;
	struct sigevent evp;
	memset(&evp, 0, sizeof(struct sigevent));		//清零初始化

	evp.sigev_value.sival_int = 111;			//也是标识定时器的，这和timerid有什么区别？回调函数可以获得
	evp.sigev_notify = SIGEV_THREAD;			//线程通知的方式，派驻新线程
	evp.sigev_notify_function = timer_thread;		//线程函数地址

	if (timer_create(CLOCKID, &evp, &timerid) == -1)
	{
		perror("fail to timer_create");
		exit(-1);
	}

	// XXX int timer_settime(timer_t timerid, int flags, const struct itimerspec *new_value,struct itimerspec *old_value);
	// timerid--定时器标识
	// flags--0表示相对时间，1表示绝对时间
	// new_value--定时器的新初始值和间隔，如下面的it
	// old_value--取值通常为0，即第四个参数常为NULL,若不为NULL，则返回定时器的前一个值
	
	//第一次间隔it.it_value这么长,以后每次都是it.it_interval这么长,就是说it.it_value变0的时候会装载it.it_interval的值
	struct itimerspec it;
	it.it_interval.tv_sec = 1;
	it.it_interval.tv_nsec = 0;
	it.it_value.tv_sec = 1;
	it.it_value.tv_nsec = 0;

	if (timer_settime(timerid, 0, &it, NULL) == -1)
	{
		perror("fail to timer_settime");
		exit(-1);
	}

	pause();

	return 0;
}
/*
 * int timer_gettime(timer_t timerid, struct itimerspec *curr_value);
 * 获取timerid指定的定时器的值，填入curr_value
 *
 */