Question

我已经编写了该程序，该程序正在扫描文件夹，并希望在用户输入“q＆＃39;”时始终停止运行。在胜利它简单 - getch（）功能。在Linux中，它更难做到，如果我想在win和linux中运行我的程序，我的老师告诉我使用线程。问题是如何？我已经写过像这样的文字：

void exit_stat()
{
            int x=0;
    char d;
    while(x==0)
    {
        d=getchar();
        if(d=='q')
        exit;
    }
}

并在主要：

pthread_t threads[1];
pthread_create(&threads[0], NULL, exit_stat, NULL);

如何解决？

Answer 1

你需要exit(0);，如果你exit;（概念上）查找一个函数指针，然后抛出它而不调用它。致电exit相当于从return执行main。

Answer 2

你可以让你的main（）监视stdin，然后当它收到用户的'q'命令时，让它告诉你的扫描线程消失。在C ++中你可以使用std :: atomic boolean来很容易地做到这一点，但是既然你问过C，这里有一个使用套接字对来做通知的解决方案。特别是，当main（）线程希望scan_thread终止时，它通过关闭自己的套接字对连接结束来表示需要。 scan_thread检测到连接已关闭，并通过终止自身来响应。

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/socket.h>

static void * scan_thread(void * socketPtr)
{
   int socket1 = *((int *)socketPtr);

   while(1)
   {
      printf("scan_thread:  I'm scanning more files!\n");
      sleep(1);  /* well, I'm pretending to, anyway */

      /* See if the main thread has closed his end of the socket-connection yet.
       * If so, that means it is time for us to clean up and exit.
       */
      char buf;
      int r = recv(socket1, &buf, 1, 0);
      if (r == 0) break;  /* recv() returning 0 indicates that the socket connection has been broken */
   }
   printf("scan_thread is exiting now!\n");

   close(socket1);  /* make sure we don't leak our socket */
   return NULL;
}

int main(int argc, char ** argv)
{
   /** Create a pair of sockets that are connected to each other */
   int sockets[2];
   if (socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) != 0)
   {
      perror("socketpair");
      return 10;
   }

   /** Make socket[1] non-blocking so that the scan_thread can check its status without blocking */
   int flags = fcntl(sockets[1], F_GETFL, 0);
   if (fcntl(sockets[1], F_SETFL, flags|O_NONBLOCK) != 0)
   {
      perror("fcntl");
      return 10;
   }

   /** spawn the child thread.  Pass him a pointer to his socket, as an argument. */
   pthread_t thread;
   if (pthread_create(&thread, NULL, scan_thread, &sockets[1]) != 0)
   {
      perror("pthread_create");
      return 10;
   }

   char buf[128];
   while(fgets(buf, sizeof(buf), stdin))
   {
      if (buf[0] == 'q')
      {
         printf("You typed q, time to abort the thread!\n");
         break;
      }
   }

   /** Close our socket.  That will let the scan_thread know its time for him to exit. */
   close(sockets[0]);

   /** Wait for the scan_thread to exit (this is important, to avoid race conditions). */
   (void) pthread_join(thread, NULL);

   printf("main() is ending, bye!\n");
   return 0;
}

但请注意，您的老师对于必要的线程并不完全正确;通过将stdin设置为非阻塞模式，您可以从Linux下的stdin获得非阻塞读取行为。这是一个程序的例子，它可以在不产生任何额外线程的情况下执行相同的操作：

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char ** argv)
{
   /** Set stdin to non-blocking mode so we can read from it without blocking */
   int fd = fileno(stdin);
   int flags = fcntl(fd, F_GETFL, 0);
   if (fcntl(fd, F_SETFL, flags|O_NONBLOCK) != 0)
   {
      perror("fcntl");
      return 10;
   }

   while(1)
   {
      printf("I'm scanning more files!\n");
      sleep(1);  /* well, I'm pretending to, anyway */

      char buf[128];
      if ((fgets(buf, sizeof(buf), stdin))&&(buf[0] == 'q'))
      {
         printf("You entered q, exiting now!\n");
         break;
      }
   }
   return 0;
}

如何在c中使用线程中止程序？

2 个答案: