Fork（）和父/子进程

Question

这是关于我的作业以及老师对输出的期望的问题。。。我对从此处输入的代码感到困惑。 我的输出是数千个子进程和父进程

#include <stdio.h>
#include <unistd.h>

main()
{
/* Create three variables */
/* One to create a fork */
/* One to store a value */
/* One to use as a count control for a loop */

/* Initialize value variable here */ ;

printf("Ready to fork...\n");

/* Create fork here */

if ( /* Condition to determine if parent */ )
{
        printf( "The child executes this code.\n" );
        for (  /* Count control variable set to zero, less than five, incremented */  )
         /* Value variable */  =  /* What does value variable equal? */ ;
        printf( "Child = /* The ending value variable goes here */ " );
     }
else
    {
         for (  /* Count control variable set to zero, less than five, incremented */  )
            /* Value variable */  =  /* What does value variable equal? */ ;
        printf("Parent = /* The ending value variable goes here */ ");

    }
}

Here is the output from my program:
Ready to fork...
The parent executes this code.
Parent = 3
The child executes this code.
Child = 10

这就是我的代码

#include <stdio.h>
#include <unistd.h>

main()
{
/* Create three variables */
int frk;
int val;
int count;

val=0;

printf("Ready to fork...\n");

frk=fork();

if ( frk==0 )
{
                printf( "The child executes this code.\n" );
                for (count=0; count<5; count++  )
                val  = frk ;
                printf( "Child = %d\n",val );
         }
else
        {
                 for (count=0; count<5; count++  )
                val  =  frk;
                printf("Parent = %d\n ",val);

        }
}

Answer 1

编写的练习有点令人困惑，但是在我看来，作者的理解是：

您的程序只包含一个“值”变量：我们称它为val 。

在程序调用fork() ，子进程应将val设置为10，而父进程将其设置为3。 即使它们都运行相同的代码，名称val指代子进程和父进程在内存中的不同位置。

换句话说，您不需要指望fork()返回3或10。在运行了一个简短的for(...)循环之后，您只需将父进程设置为val = 3并将子进程设置为val = 10 。

if (frk == 0) {
    ...
    val = 10;
    printf("Child = %d\n", val);
}
else {
    ...
    val = 3;
    printf("Parent = %d\n", val);
}