struct StructOfTimerStatus
{
    unsigned int count;                               //計數值
    unsigned int flag;                                //定時標志
}
;

struct StructOfTimer
{ 
    struct StructOfTimerStatus      testtime;   //測試定時器
}
mytime;

void SetTimer(int sec,int usec);
void SigalrmFunc(void);

//定時器函數
/*******************************************************************************
* Discription:SIGALRM 信號響應函數；用作定時器
* Input      :
* Output    :
*******************************************************************************/
void SigalrmFunc(void)
{
    if(mytime.testtime.count++>20)      //定時1秒,20*50000=1s
    {
        mytime.testtime.flag=1;
        mytime.testtime.count=0;
    }
}

void SetTimer(int sec,int usec)
{
    struct itimerval value,ovalue;
    signal(SIGALRM,(void *)SigalrmFunc);

    value.it_value.tv_sec = sec;
    value.it_value.tv_usec = usec;
    value.it_interval.tv_sec = sec;
    value.it_interval.tv_usec = usec;

    setitimer(ITIMER_REAL,&value,&ovalue); 
}

int main(int argc, char **argv)
{
    SetTimer(0, 50000);
    while(1)
    {
        if(mytime.testtime.flag == 1)
        {
            mytime.testtime.flag = 0;
            system("clear");
            printf("Timing success\n");
        }
    }
    return 0;
}