华清day4 24-7-31

1> 使用父子进程完成两个文件的拷贝

父进程拷贝前一半内容，子进程拷贝后一半内容

子进程结束后退出，父进程回收子进程的资源

/* 
使用父子进程完成两个文件的拷贝父进程拷贝前一半内容，子进程拷贝后一半内容
子进程结束后退出，
父进程回收子进程的资源
*/
#include<myhead.h>
int main(int argc, const char *argv[])
{char buf[128] = " ";//定义搬运工int count = 0,n =0,num = 0;pid_t pid =-1;pid = fork();//创建子进程if(pid>0)//父进程执行的代码{int src = -1;if((src = open("./01dir.c",O_RDONLY))== -1)//被复制的文件以只读的形式打开{perror("src open error");return -1;}int dest = -1;if((dest = open("./zy.txt",O_RDWR|O_CREAT|O_TRUNC,0665))== -1)//被复制的文件以w+的形式打开{perror("dest open error");return -1;}n = (lseek(src, 0, SEEK_END)+1)/2;//遇到奇数时候确保能复制一半所以+1lseek(src, 0, SEEK_SET);//光标while(1){count = read(src,buf,sizeof(buf));num +=count;if(num >n){write(dest,buf,n%sizeof(buf));break;}write(dest,buf,count);}	printf("父进程\n");}else if(pid == 0)//子进程执行的代码{sleep(0.1);//确保子进程在父进程之后int src = -1;if((src = open("./01dir.c",O_RDONLY))== -1)//被复制的文件以只读的形式打开{perror("src open error");return -1;}int dest = -1;if((dest = open("./zy.txt",O_RDWR|O_CREAT|O_APPEND,0665))== -1)//目标文件以追加的方式打开{perror("dest open error");return -1;}lseek(dest,20,SEEK_SET);n = (lseek(src, 0, SEEK_END)+1)/2;//遇到奇数时候确保能复制一半所以+1lseek(src, n, SEEK_SET);//光标偏移到下半开始的地方while(1){count = read(src,buf,sizeof(buf));if(count ==0){break;}write(dest,buf,count);}		printf("子进程\n");}exit(0);wait(NULL);return 0;
}

2> 详细绘制思维导图