多进程思维导图

1> 思维导图

2> 使用父子进程完成两个文件的拷贝，父进程拷贝前一半，子进程拷贝后一半，两个进程同时进行（君子作业）

#include <myhead.h>
typedef struct sockaddr_in addr_in_t;
typedef struct sockaddr addr_t;
typedef struct sockaddr_un addr_un_t;

void zijincheng(int wfd,int rfd,int guang_biao){
	lseek(wfd,guang_biao/2,SEEK_SET);
	lseek(rfd,guang_biao/2,SEEK_SET);
	char ch ;
	for(int i=0;i<guang_biao/2;i++){
		int res = read(rfd,&ch,1);
		write(wfd,&ch,1);
		//if()abreak;
	}
	exit(0);

}
int main(int argc, const char *argv[])
{

	pid_t pid = fork();	
	int wfd = open(argv[2],O_WRONLY|O_CREAT|O_TRUNC,0664);
	if(wfd==-1){
		perror("write err:");
	}
	int rfd = open(argv[1],O_RDONLY);
	if(rfd==-1){
		perror("read err:");
	}


	int guang_biao = lseek(rfd,0,SEEK_END);
	if(pid == 0){
	zijincheng(wfd,rfd,guang_biao);
		//exit(0);
	}
	char ch;

	lseek(rfd,0,SEEK_SET);
	for(int i=0;i<guang_biao/2;i++){
		read(rfd,&ch,1);
		write(wfd,&ch,1);
	//	if(res == 0)break;
	}
	wait(NULL);

	return 0;
}