如何通过管道将hping3的输出从子节点传递到父节点？

Question

我最近问了一个关于如何在c程序中调用hping3的问题。提供的解决方案是有效的，但我现在有另一个问题。hping3的输出必须传递给父进程，因此我执行了以下操作。请注意，这只是代码片段，我认为bug在其中。下面的代码片段在一个循环中运行，我在循环中遍历了一系列ip地址，这对于在我的mpi程序中提供两种不同的分发策略是必要的。

//Stick together the params
sprintf(params, "--scan %u %u.%u.%u.%u -V", *(portarray + i), (iterator & 0xFF000000)>>24, (iterator & 0x00FF0000)>>16, (iterator & 0x0000FF00)>>8, (iterator & 0x000000FF));
            //Pipe and check status
            if(pipe(pipes)==-1){
               perror("Error piping");
            }
            //Fork and check status
            pid=fork();
            if(pid == -1){
               perror("Error forking");
            } else if(pid > 0){
               //Parent does not write
               close(pipes[1]);
               //Save stdout from pipe
               nbytes = read(pipes[0], buffer, sizeof(buffer));
               //Parent, wait for child
               waitpid(pid, &status, 0);
               //Print out pipe
               printf("hping3: (%.*s)\n", nbytes, buffer);
               wait(NULL);
               close(pipes[0]);
            } else {
               //Child does not read
               close(pipes[0]);
               //Map stdout and stderr to write pipe-end
               dup2(pipes[1], 1);
               dup2(pipes[1], 2);
               //Child, exec hping with params
               execl("sudo /usr/sbin/hping3","sudo /usr/sbin/hping3",params,NULL);
               close(pipes[1]);
               //Exit child to prevent fork-bomb
               return 0;
            }
            //Sleep for specified delaytime
            sleep((unsigned int)delay);

我不知道问题出在哪里。输出如下(当然是在循环中)：

hping3()

hping3程序输出到stdout和stderr，我通过输出重定向到一个文件在shell上对其进行了测试。

Answer 1

buffer是如何定义的？你有没有检查过nbytes的值？您确定正在执行hping吗？我会尝试以下几点：

int buffsize  = 100;
char * buffer = malloc(buffsize);

if (pid == -1) {
   perror("Error forking");
} else if (pid > 0) {
   //Parent does not write
   close(pipes[1]);
   // I'd first wait for the child to finish.
   waitpid(pid, &status, 0);
   // Save stdout from pipe 
   // recall that sizeof(buffer) != buffsize when malloc'ed.
   int count = 0;
   while((nbytes = read(pipes[0], buffer+count, buffsize-count) != -1) count += nbytes;
   //Print out pipe
   printf("hping3: (%.*s)\n", nbytes, buffer);
   wait(NULL);
   close(pipes[0]);
} else {
   //Child does not read
   close(pipes[0]);
   //Map stdout and stderr to write pipe-end
   dup2(pipes[1],1);
   dup2(pipes[1],2);
   // Close pipes[1]
   close(pipes[1]);
   //Child, exec hping with params
   if (execl("sudo /usr/sbin/hping3","sudo /usr/sbin/hping3",params,NULL) == -1)
      perror("execl error");
   //Exit child to prevent fork-bomb
   return 0;
}