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我正在尝试在代码中实现计时器，我发现的所有示例都在使用while(1)或者for(;;)但是当我尝试使用scanf我的程序时终止。它是否有任何价值，stdin因为如果我使用scanf两次，那么在退出程序之前会调用两次计时器。这是我的示例代码：

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

#include <linux/socket.h>
#include <time.h>


#define SIGTIMER (SIGRTMAX)
#define SIG SIGUSR1
static timer_t     tid;
static timer_t     tid2;

void SignalHandler(int, siginfo_t*, void* );
timer_t SetTimer(int, int);

int main(int argc, char *argv[]) {

    int t;

    printf("SIGRTMAX %d\n", SIGRTMAX);
        printf("SIGRTMIN %d\n", SIGRTMIN);

    struct sigaction sigact;
    sigemptyset(&sigact.sa_mask);
    sigact.sa_flags = SA_SIGINFO;
    sigact.sa_sigaction = SignalHandler;
    // set up sigaction to catch signal
    if (sigaction(SIGTIMER, &sigact, NULL) == -1) {
        perror("sigaction failed");
        exit( EXIT_FAILURE );
    }

    // Establish a handler to catch CTRL+c and use it for exiting.
    sigaction(SIGINT, &sigact, NULL);
    tid=SetTimer(SIGTIMER, 1000);

    struct sigaction sa;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_SIGINFO;
    sa.sa_sigaction = SignalHandler;
    // set up sigaction to catch signal
    if (sigaction(SIG, &sa, NULL) == -1) {
        perror("sa failed");
        exit( EXIT_FAILURE );
    }

    // Establish a handler to catch CTRL+c and use it for exiting.
    sigaction(SIGINT, &sa, NULL);
    tid2=SetTimer(SIG, 1000);

   // for(;;);  or while(1) Working properly

    scanf("%d", &t); /// Program terminates
    return 0;
}

void SignalHandler(int signo, siginfo_t* info, void* context)
{


    if (signo == SIGTIMER) {
        printf("Command Caller has ticked\n");

    }else if (signo == SIG) {
        printf("Data Caller has ticked\n");

    } else if (signo == SIGINT) {
        timer_delete(tid);
        perror("Crtl+c cached!");
        exit(1);  // exit if CRTL/C is issued
    }
}
timer_t SetTimer(int signo, int sec)
{
    static struct sigevent sigev;
    static timer_t tid;
    static struct itimerspec itval;
    static struct itimerspec oitval;

    // Create the POSIX timer to generate signo
    sigev.sigev_notify = SIGEV_SIGNAL;
    sigev.sigev_signo = signo;
    sigev.sigev_value.sival_ptr = &tid;

    if (timer_create(CLOCK_REALTIME, &sigev, &tid) == 0)
    {

        itval.it_value.tv_sec = sec / 1000;
        itval.it_value.tv_nsec = (long)(sec % 1000) * (1000000L);
        itval.it_interval.tv_sec = itval.it_value.tv_sec;
        itval.it_interval.tv_nsec = itval.it_value.tv_nsec;



        if (timer_settime(tid, 0, &itval, &oitval) != 0)
        {
            perror("time_settime error!");
        }
    }
    else
    {
        perror("timer_create error!");
        return NULL;
    }
    return tid;
}

那么，我该如何解决这个问题呢？任何帮助，将不胜感激。谢谢，尤维

4

2 回答 2

4

信号中断scanf。如果perror('scanf')在 scanf 之后添加，输出将是：

SIGRTMAX 64
SIGRTMIN 34
命令调用者已勾选
数据呼叫者已打勾
scanf：中断的系统调用

如果您替换scanf为：

做 {
    错误号 = 0;
    scanf("%d", &t);
} while(errno == EINTR);

scanf 将在失败时重试Interrupted system call。

于 2012-04-10T10:20:30.300 回答
2

您绝对不能在信号处理程序中使用printfand 。perror他们不能重入。

此外，如果您的程序在其中接收到信号，则可能scanf会返回错误。如果scanf返回 EOF，请检查errno，它可能是EINTR.

于 2012-04-10T10:21:26.800 回答