如何在 C++ linux 中将系统调用转换为 fork

Question

这是在C++ linux代码中播放声音文件的代码

 string str1 = "aplay ";
 str1 = str1 + " out.wav" + " & ";
 const char *command = str1.c_str();
 system(command);

** 完整代码在这里：Playing sound C++ linux aplay : device or resource busy

我只是想知道如何在 fork() 中播放这个，因为我读到系统调用对 cpu 的负担太大，这当然是我的情况。 请帮忙

Answer 1

fork 将复制您的流程，以便您轻松编写：

// fork the current process: beyond this point, you will have 2 process
int ret = fork();
if (ret == 0) {
   // in child: execute the long command
   system("aplay out.wav");
   // exit the child process
   exit(0);
}

// child process will not go here

if (ret < 0) {
    perror("fork");
}

---

之后，您应该知道system 会为您服务fork + exec + wait。既然你不希望你的父进程等待子进程，你可以这样写：

// fork the current process: beyond this point, you will have 2 process
int ret = fork();
if (ret == 0) {
   // in child: execute the long command
   char program[] = "/usr/bin/aplay";
   char *args[] = {"/usr/bin/aplay", "out.wav" };
   ret = execv(program, args); 

  // this point will be reach only if `exec` fails
  // so if we reach this point, we've got an error.
  perror("execv");

  exit(0);
}

// child process will not go here

if (ret < 0) {
    perror("fork");
}