linux下定时器timer_create()的使用

一、采用新线程派驻的方式 （注： 编译时 需加上 -lrt）

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


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

int init_timer(timer_t *timerid, struct sigevent *evp, struct itimerspec *it)
{
    if ( !evp || !it )
        return -1;

    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(CLOCK_REALTIME, evp, timerid) == -1)  
    {  
        perror("fail to timer_create");  
        return -1;;  
    }  

    printf("timer_create timerid = %d\n", *timerid);
    it->it_interval.tv_sec = 1;  // 后续按照该时间间隔 
    it->it_interval.tv_nsec = 0;  
    it->it_value.tv_sec = 3;     // 最初开始时间间隔 
    it->it_value.tv_nsec = 0;  

    return 0;
}

int start_timer(timer_t *timerid, struct itimerspec *it)
{
    if (it == NULL){
        return -1;
    }
    if (timer_settime(*timerid, 0, it, NULL) == -1)  
    {  
        perror("fail to timer_settime");  
        return -1;
    }  
    
    return 0;
}

void thread_func(void *param)
{
    int *a = (int *)param;
    while(1){
        sleep(1);
        printf("This is thread..\n");
    }

    *a = 100;
    printf("param = %d\n", *a);
}

int main(int argc, const char *argv[])
{
    pid_t pid = 0;
    pthread_t thread;
    timer_t timerid = 0;
    int ret;
    struct sigevent evp;  
    struct itimerspec it;  

    int a = 10;    
#if 0

    int ret = init_timer(&timerid, &evp, &it);
    if (ret < 0){
        printf("init_timer failed\n");
        return -1;
    }
#endif
  
    if ((pid = fork()) < 0)
    {
        printf("fork failed.\n");
        return -1;
    }
    else if ( pid == 0){
        printf("child proc..\n");

        ret = pthread_create(&thread, NULL, thread_func, &a);

        int ret = init_timer(&timerid, &evp, &it);
        if (ret < 0){
            printf("init_timer failed\n");
            return -1;
        }
        sleep(2);
        printf("child timer_Id addr = %d\n", timerid);
        start_timer(&timerid, &it);

        sleep(10);
        exit(0);
    }
    else{
        printf("I'm parent proc..\n");
        printf("parent timer_Id addr = %d\n", timerid);
        printf("pthread_id = %d\n", thread);
        do {
            ret = waitpid(pid, NULL, WNOHANG);
            if (ret == 0){
                printf("No child exit\n");
                sleep(2);
            }
            else if (ret == pid){
                printf("Successly get child %d\n", pid);
            }
            else
                printf("something error\n");
        }while(ret == 0);
    
        /*ret = waitpid(pid, NULL, 0);*/
        /*if (ret == pid)*/
            /*printf("successly get child %d\n", pid);*/

    }
    pause();
    return 0;
}#include <stdi