Fork() 的跟踪问题

Question

我有这个 fork() 的例子，我需要做一个跟踪！

#include <unistd.h>

int main(void) {
    int i;
    for (i=0; i<3; i++)
        if (fork()) 
            wait(NULL);
    return 0;
}

我的跟踪解决方案是，出了点问题，我不知道如何进行跟踪：

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main(void) {

    int i,pid;

    for(i=0;i<3;i++) {

        pid=fork();

        if(pid>0) ///if is father (true)
            printf("PID After the fork child === %d  & father === %d (i = %d) \n\n",(int)getpid,(int)getppid,i);

        wait(NULL);

        printf(" After the wait  child=== %d  & father=== %d (i = %d)|||\n",(int)getpid,(int)getppid,i);
    }
}

这是我在终端中得到的。我可以清楚地看到它是不正确的，但我不知道如何解决这个问题：

PID After the fork child === 134513568  & father === 134513632 (i = 0) 

After the wait  child=== 134513568  & father=== 134513632 (i = 0)|||
PID After the fork child === 134513568  & father === 134513632 (i = 1) 


After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 1)|||
PID After the fork child === 134513568  & father === 134513632 (i = 2) 

After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 0)|||
PID After the fork child === 134513568  & father === 134513632 (i = 1) 

After the wait  child=== 134513568  & father=== 134513632 (i = 1)|||
PID After the fork child === 134513568  & father === 134513632 (i = 2) 

After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 1)|||
PID After the fork child === 134513568  & father === 134513632 (i = 2) 

After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||
After the wait  child=== 134513568  & father=== 134513632 (i = 2)|||

谢谢。

Answer 1

您对printf() 的参数是getpid 和getppid——当您似乎打算打印调用这些函数的结果时，您正在传递这些函数的地址。打电话给他们...

printf("PID After the fork child === %d  & father === %d (i = %d) \n\n",(int)getpid(),(int)getppid(),i);

Answer 2

我认为你错过了大括号和方括号：

   if(pid>0) ///if is father (true) 
   {        
       printf("PID After the fork child === %d  & father === %d (i = %d) \n\n",(int)getpid(),(int)getppid(),i);

       wait(NULL);

      printf(" After the wait  child=== %d  & father=== %d (i = %d)|||\n",(int)getpid(),(int)getppid(),i);
  }

在您的代码中，第二个printf ("After the wait ...) 将在父进程和子进程中调用。