2.2创建进程函数fork的使用（第二阶段）

2.2创建进程函数fork的使用（第二阶段）

使用fork函数创建一个进程
pid_t fork(void);

fork函数调用成功，返回两次
返回值为0，代表当前进程是子进程
返回值非负数，代表当前进程为父进程
调用失败，返回-1

代码展示

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

int main()
{
	pid_t pid;
	
	pid = getpid();
		
	printf("my pid is %d\n",pid);

	while(1);

	return 0;
}

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

int main()
{
	pid_t pid;
	
	pid = getpid();
		
	fork();
	
	printf("my pid is %d\n",pid);


	return 0;
}

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

int main()
{
	pid_t pid;
	
	pid = getpid();
		
	fork();
	
	printf("my pid is %d , current pro id:%d\n",pid,getpid());


	return 0;
}

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

int main()
{
	pid_t pid;
	pid_t pid2;	

	pid = getpid();
	
	printf("before fork:pid = %d\n",pid);
		
	fork();


	pid2 = getpid();
	
	printf("after fork:pid = %d\n",pid2);
	
	
	if(pid == pid2){

		printf("this is father print\n");
	}else{

		printf("this is child print,child pid = %d\n",getpid());
	}


	return 0;
}

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

int main()
{
	pid_t pid;
	pid_t pid2;	

	printf("father id:%d\n",getpid());

	pid = fork();
	
	
	if(pid > 0){

		printf("this is father print:%d\n",getpid());
	}else if(pid == 0){

		printf("this is child print,child pid = %d\n",getpid());//当pid等于0时为子进程
	}


	return 0;
}