变量在不同进程中是相互独立的一个例子

    将下面的程序保存到fork.c里面。从运行的结果看，父子进程中的局部变量或者全局变量都没有被彼此影响。

?#include<stdio.h>
#include<signal.h>
#include <stdlib.h>
//#include <unistd.h>
//变量在不同进程中是相互独立的
int wait_mark;
int g_temp = 21;
void waiting()
{
    while (wait_mark == 1);
}

void stop()
{
    wait_mark = 0;
}

int main()
{
    int p1, p2;
    int temp = 3;
    while ((p1 = fork()) == -1);
if (p1 == 0) //第一个子进程
{
        wait_mark = 1;
        printf("Child Process11 temp1 = %d \n",temp);
        printf("Child Process11 g_temp1 = %d \n",g_temp);
        signal(SIGINT, SIG_IGN);//忽略来自键盘的中断信号 ( ctrl + c )
        signal(16, stop);
        waiting();
        lockf(1, 1, 0); //加锁
        printf("Child Process11 is Killed by Parent!\n");
        printf("Child Process11 temp2 = %d \n",temp);
        temp = 6;
        printf("Child Process11 g_temp2 = %d \n",g_temp);
        g_temp = 23;
        lockf(1, 0, 0); //解锁
        exit(0);
}
else
{
        while ((p2 = fork()) == -1);
        if (p2 == 0) //第二个子进程
{
            wait_mark = 1;
            printf("Child Process12 temp1 = %d \n",temp);
            printf("Child Process12 g_temp1 = %d \n",g_temp);
            signal(SIGINT, SIG_IGN);//忽略来自键盘的中断信号 ( ctrl + c )
            signal(17, stop);
            waiting();
            lockf(1, 1, 0); //加锁
            printf("Child Process12 is Killed by Parent!\n");
            printf("Child Process12 temp2 = %d \n",temp);
            temp = 5;
            printf("Child Process12 g_temp2 = %d \n",g_temp);
            g_temp = 24;
            lockf(1, 0, 0);//解锁
            exit(0);
        }
else//父进程
{
            wait_mark = 1;
            temp = 4;
            g_temp = 22;
            printf("Parent temp1 = %d \n",temp);
            printf("Parent g_temp1 = %d \n",g_temp);
            signal(SIGINT, stop);//注册来自键盘的中断信号 ( ctrl + c ) ，中断后跳到stop函数中运行
            waiting();
            kill(p1, 16);
            kill(p2, 17);
            wait(0);
            wait(0);
            printf("Parent Process is Killed!\n");
            printf("Parent temp2 = %d \n",temp);
            printf("Parent g_temp2 = %d \n",g_temp);
            exit(0);
        }
    }
}

在当前目录下
[chenyun fork]$ gcc fork.c -o fork.o
结果打印如下：
[chenyun fork]$ ./fork.o
Child Process11 temp1 = 3
Child Process11 g_temp1 = 21
Parent temp1 = 4
Parent g_temp1 = 22
Child Process12 temp1 = 3
Child Process12 g_temp1 = 21

^CChild Process11 is Killed by Parent!
Child Process11 temp2 = 3
Child Process11 g_temp2 = 21
Child Process12 is Killed by Parent!
Child Process12 temp2 = 3
Child Process12 g_temp2 = 21
Parent Process is Killed!
Parent temp2 = 4
Parent g_temp2 = 22
[chenyun fork]$
注：程序运行中间按ctrl+C会中断父进程，父进程会发kill 16消息给子进程1，发kill 17消息给子进程2。