使用popen的无阻塞管道？

Question

我想打开一个管道popen()并对其进行非阻塞"读取"访问.

我怎样才能做到这一点？

(我发现的例子都是阻塞/同步的)

Answer 1

设置如下:

FILE *f = popen("./output", "r");
int d = fileno(f);
fcntl(d, F_SETFL, O_NONBLOCK);

现在你可以阅读:

ssize_t r = read(d, buf, count);
if (r == -1 && errno == EAGAIN)
    no data yet
else if (r > 0)
    received data
else
    pipe closed

当你完成后,清理:

pclose(f);

Answer 2

popen()内部调用pipe(),fork(),dup2()(指向子进程的FDS 0/1/2的管道)和execve().您是否考虑过使用这些？在这种情况下,您可以使用将您读取的管道设置为非阻塞fcntl().

更新:这是一个例子,仅用于说明目的:

int read_pipe_for_command(const char **argv)
{
   int p[2];

   /* Create the pipe. */
   if (pipe(p))
   {
      return -1;
   }

   /* Set non-blocking on the readable end. */
   if (fcntl(p[0], F_SETFL, O_NONBLOCK))
   {
      close(p[0]);
      close(p[1]);
      return -1;
   }

   /* Create child process. */
   switch (fork())
   {
      case -1:
          close(p[0]);
          close(p[1]);
          return -1;
      case 0:
          /* We're the child process, close read end of pipe */
          close(p[0]);
          /* Make stdout into writable end */
          dup2(p[1], 1);
          /* Run program */
          execvp(*argv, argv);
          /* If we got this far there was an error... */
          perror(*argv);
          exit(-1);
      default:
          /* We're the parent process, close write end of pipe */
          close(p[1]);
          return p[0];
   }
}