一、採用新執行緒派駐的方式 （注： 編譯時 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;        //也是標識定時器的，這和timerid有什麼區別？回撥函式可以獲得  
    evp->sigev_notify = SIGEV_THREAD;        //執行緒通知的方式，派駐新執行緒  
    evp->sigev_notify_function = timer_thread;   //執行緒函式地址  

    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;  // 後續按照該時間間隔 
    it->it_interval.tv_nsec = 0;  
    it->it_value.tv_sec = 3;     // 最初開始時間間隔 
    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;
}
 

二、採用通知方式為訊號（signal）的處理方式

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

void handle()  
{  
    time_t t;  
    char p[32];  
  
    time(&t);  
    strftime(p, sizeof(p), "%T", localtime(&t));  
  
    printf("time is %s\n", p);  
}  
  
  
  
int main()  
{  
    struct sigevent evp;  
    struct itimerspec ts;  
    timer_t timer;  
    int ret;  
  
    memset(&evp, 0, sizeof(struct sigevent));

    evp.sigev_value.sival_ptr = &timer;  
    evp.sigev_notify = SIGEV_SIGNAL;  
    evp.sigev_signo = SIGUSR1;  
    signal(SIGUSR1, handle);  
  
    ret = timer_create(CLOCK_REALTIME, &evp, &timer);  
    if( ret )   
        perror("timer_create");  
  
    ts.it_interval.tv_sec = 1;  
    ts.it_interval.tv_nsec = 0;  
    ts.it_value.tv_sec = 3;  
    ts.it_value.tv_nsec = 0;  
  
    ret = timer_settime(timer, 0, &ts, NULL);  
    if( ret )   
    perror("timer_settime");  
  
    while(1);  
} 
 

訊號為signaction處理函式 :

#include <stdio.h>  
#include <time.h>  
#include <stdlib.h>  
#include <signal.h>  
#include <string.h>  
#include <unistd.h>  
  
#define CLOCKID CLOCK_REALTIME  
  
void sig_handler(int signo)  
{  
    printf("timer_signal function! %d\n", signo);  
}  
  
int main()  
{  
    //XXX int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);  
    // signum--指定的訊號編號，可以指定SIGKILL和SIGSTOP以外的所有訊號編號  
    // act結構體--設定訊號編號為signum的處理方式  
    // oldact結構體--儲存上次的處理方式  
    //  
    // struct sigaction   
    // {  
    // void (*sa_handler)(int);         //訊號響應函式地址  
    // void (*sa_sigaction)(int, siginfo_t *, void *);   //但sa_flags為SA——SIGINFO時才使用  
    // sigset_t sa_mask;         //說明一個訊號集在呼叫捕捉函式之前，會加入程序的遮蔽中，當捕捉函式返回時，還原  
    // int sa_flags;  
    // void (*sa_restorer)(void);   //未用  
    // };  
    //  
    timer_t timerid;  
    struct sigevent evp;  
  
    struct sigaction act;  
    memset(&act, 0, sizeof(act));  
    act.sa_handler = sig_handler;  
    act.sa_flags = 0;  
  
    // XXX int sigaddset(sigset_t *set, int signum);  //將signum指定的訊號加入set訊號集  
    // XXX int sigemptyset(sigset_t *set);          //初始化訊號集  
      
    sigemptyset(&act.sa_mask);  
  
    if (sigaction(SIGUSR1, &act, NULL) == -1)  
    {  
        perror("fail to sigaction");  
        exit(-1);  
    }  
  
    memset(&evp, 0, sizeof(struct sigevent));  
    evp.sigev_signo = SIGUSR1;  
    evp.sigev_notify = SIGEV_SIGNAL;  
    if (timer_create(CLOCK_REALTIME, &evp, &timerid) == -1)  
    {  
        perror("fail to timer_create");  
        exit(-1);  
    }  
  
    struct itimerspec it;  
    it.it_interval.tv_sec = 2;  
    it.it_interval.tv_nsec = 0;  
    it.it_value.tv_sec = 1;  
    it.it_value.tv_nsec = 0;  
    if (timer_settime(timerid, 0, &it, 0) == -1)  
    {  
        perror("fail to timer_settime");  
        exit(-1);  
    }  
  
    pause();  
  
    return 0;  
}