如何让父级等待所有子级进程完成? [英] How to make parent wait for all child processes to finish?

问题描述

我希望有人可以阐明如何让父级等待 ALL 子进程完成后再继续执行分叉.我有要运行的清理代码，但是子进程需要先返回，然后才能发生.

I'm hoping someone could shed some light on how to make the parent wait for ALL child processes to finish before continuing after the fork. I have cleanup code which I want to run but the child processes need to have returned before this can happen.

for (int id=0; id<n; id++) {
  if (fork()==0) {
    // Child
    exit(0);      
  } else {
    // Parent
    ...
  }
  ...
}

推荐答案

pid_t child_pid, wpid;
int status = 0;

//Father code (before child processes start)

for (int id=0; id<n; id++) {
    if ((child_pid = fork()) == 0) {
        //child code
        exit(0);
    }
}

while ((wpid = wait(&status)) > 0); // this way, the father waits for all the child processes 

//Father code (After all child processes end)

wait 等待 a 子进程终止，并返回该子进程的pid.发生错误时(例如，当没有子进程时)，返回-1.因此，基本上，代码会一直等待子进程完成，直到wait ing错误出来，然后您就知道它们都已完成.

wait waits for a child process to terminate, and returns that child process's pid. On error (eg when there are no child processes), -1 is returned. So, basically, the code keeps waiting for child processes to finish, until the waiting errors out, and then you know they are all finished.

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