linux定时器

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

#include <signal.h>
#include <sys/time.h>

void Demo_updateTime(int signo)
{
    printf("timer comer.\n");
}

int main(int argc, char *argv[])
{
    struct itimerval oneSec;

    signal(SIGALRM, Demo_updateTime);
    oneSec.it_value.tv_sec = 1;
    oneSec.it_value.tv_usec = 0;
    oneSec.it_interval.tv_sec = 1;
    oneSec.it_interval.tv_usec = 0;
    setitimer(ITIMER_REAL, &oneSec, NULL);

    while(1)
        sleep(9999);
}

去掉while(1)这一行只执行一次定时器；不解释。