c - fork 及其功能？

Question

我有以下代码，并被问到“A”、“B”、“C”、“D”、“E”将被打印多少次

fun() {
  printf("A");
  fork();
  printf("B");
  if (fork() != 0) {
     printf("C");
     fork();
     printf("D");
  }
  printf("E");
}

应该是:

A
A 
B
E

我不确定我上面的回答是否正确？ if(fork() !=0 ) 这行是做什么的？

Answer 1

来自documentation :

On success, the PID of the child process is returned in the parent, and 0 is returned in the child. On failure, -1 is returned in the parent, no child process is created, and errno is set appropriately.