Linux进程编程demo3创建进程函数fork的使用补充.c

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

int main()
{
	pid_t pid;
	pid_t pid2;
	pid_t retpid;
	
	pid = getpid();
	printf("before fork:id = %d\n",pid);
	
	retpid = fork();
	//fork返回值大于0就是父进程（而这个大于0的值刚好是子进程的pid）   fork返回值等于0就是子进程
	pid2 = getpid();
	printf("after fork:id =%d\n",pid2);
	
	if(pid == pid2){
		printf("this is father :retpid=%d\n",retpid);
	}
	else if(pid != pid2){
		printf("this is child :retpid=%d,pid=%d\n",retpid,pid2);
	}
	
	
	
	return 0;
}```