c - fork 和pid

Question

代码:

int main(void) 
{
    printf("pid: %d\n", getpid());
    pid = fork();


    if (pid < 0) {
        fprintf(stderr, "Fork Failed!");
        exit(-1);
    } else if (pid == 0) {
        execv("sum", argv);
    } else {
        printf("  pid: %d\n", pid);
        wait(NULL);
    }
}

输出:

pid: 280
   pid: 281

问题:

为什么两个pid不同。我认为它们应该相同，因为父级是在 else block 中执行的，而父级是在 fork 之前执行的，所以它们应该相同，不是吗？

Answer 1

RETURN VALUE
       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.

因此，在父进程中，fork() 返回创建的子进程的 pid。