fork（）和父/子进程ID

本文介绍了fork（）和父/子进程ID的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我对以下两个程序中的子进程为什么显示不同的父代id感到困惑。

I am a bit confused about why the child process in the following two programs is showing different parents ids.

 int main ( void ) {
   int pid, fpid, ppid;
   fpid = fork ();
   pid = getpid();
   ppid = getppid();
   printf ("fpid is %d\n", fpid);
   sleep(5);
   if (fpid > 0){
       printf ("\nThis is Parent. My pid %d. My parent's pid %d\n",pid,ppid);
   }
   else if (fpid ==0){
       sleep(1);
       printf ("\nThis is Child. My pid %d. My parent's pid %d\n",pid,ppid);
   }
   else
       printf ("fork failed\n");
   return (0);
}

输出：

fpid is 53560
fpid is 0

This is Parent. My pid 53559. My parent's pid 44632

MacBook-Pro:~/Desktop/$

This is Child. My pid 53560. My parent's pid 53559

第二程序：

Second program:

int main ( void ) {
   int pid, fpid, ppid;
   fpid = fork ();
   printf ("fpid is is %d\n", fpid);
   sleep(5);
   if (fpid > 0){
       pid = getpid();
       ppid = getppid();
       printf ("\nThis is Parent. My pid %d. My parent's pid %d\n",pid,ppid);
   }
   else if (fpid ==0){
       sleep(1);
       pid = getpid();
       ppid = getppid();
       printf ("\nThis is Child. My pid %d. My parent's pid %d\n",pid,ppid);
   }
   else
       printf ("fork failed\n");
   return (0);
}

输出：

fpid is is 53635
fpid is is 0

This is Parent. My pid 53634. My parent's pid 44632

MacBook-Pro:~/Desktop$

This is Child. My pid 53635. My parent's pid 1

我知道流程1是接管流程原始父级终止后，其父级会终止。我想我想知道的是：在两种情况下，子进程都不能先完成父进程，然后子进程才能处理其 printf 吗？输出不应该相同吗？

I understand that process 1 is the process that takes over as a parent once the original parent terminates. I guess what I want to know is: isn't the parent process being finished before the child process can process its printf in both cases? Shouldn't the outputs be the same?

waitpid