fork_sample.c

来自「Linux网络编程PPT和源码,供学习参考」· C语言 代码 · 共 58 行

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

int main(int argc,char *argv[])
{
	pid_t child;
	int i=0,j=0;
	int w=20;
	pid_t who;
	int state;
	char message[128];
	child=fork();	//创建子进程
	if (child==0)	
	{
		int k;
		i=3;
		w=100;
		printf("a child w=%d\n",w);	//w为全局变量,会被修改
		sleep(3);
		strcpy(message,"i'm a child");	
		printf("a child id %d\n",getpid());	//打印子进程的PID
		exit(7);	//退出,返回7
	}
	else if(child>0)
	{
		i=5;
		printf("w value=%d\n",w);	//打印全局变量w的值,与子进程无关
		printf("parent id=%d\n",getpid());
		strcpy(message,"i'm parent");	
	}
	child=fork();	//再创建一个子进程
	if(child==0)
	{
	     printf("b child id=%d\n",getpid());	//打印第二个子进程的PID
	     sleep(5);
	     exit(4);
	}
	waitpid(child,&state,WNOHANG);	//不等待第二个子进程结束,不挂起父进程继续运行
	printf("child not finish\n");
	while((who=waitpid(-1,&state,0))>0)	//等待所有子进程结束,返回子进程PID
	{
		if(WIFEXITED(state))	//子进程正常结束(宏定义)
		{
			printf("child exit code %d\n",WEXITSTATUS(state));	
			printf("parent child id %d\n",who);
		}
	}
	//printf("parent child id %d\n",who);
	for(j=0;j<i;j++)
	{
		printf("%s\n",message);
		sleep(1);
	}
	sleep(10);
	return 0;
}