2024/4/3 IOday5-编程知识

1：实现文件夹的拷贝功能
注意判断被拷贝的文件夹是否存在，如果不存在则提前创建，创建文件夹的函数为 mkdir
不考虑递归拷贝的问题

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/wait.h>
#include <pthread.h>
#include <dirent.h>
int main(int argc, const char *argv[])
{DIR* fd1=opendir("./file1");//打开被复制文件夹if(fd1==NULL){perror("opendir");if(mkdir("./file1",S_IRWXU|S_IRWXG|S_IRWXO)==-1){perror("mkdir");return -1;}}DIR* fd2=opendir("./file2");//打开目的文件夹if(fd2==NULL){perror("opendir");if(mkdir("./file2",S_IRWXU|S_IRWXG|S_IRWXO)==-1){perror("mkdir");return -1;}}	while(1){//循环读取文件夹,循环文件printf("111111\n");struct dirent *filedir=readdir(fd1);//读取文件夹内容if(filedir==NULL){return 0;}printf("33333\n");char buf[256]={0};//定义字符数组存储文件夹中文件名memset(buf,0,sizeof(buf));strcpy(buf,"./file1/");printf("444\n");strcat(buf,filedir->d_name);//复制文件名到字符数组if(strcmp(buf,"./file1/.")&&strcmp(buf,"./file1/..")){printf("%s\n",buf);int fp1=open(buf,O_RDONLY);//文件IOchar buf2[256]={0};strcpy(buf2,"./file2/");strcat(buf2,filedir->d_name);printf("%s\n",buf2);int fp2=open(buf2,O_WRONLY|O_CREAT|O_TRUNC,0664);//在文件夹file2中创建file1中文件char str[20]={0};	while(1){//循环文件内容printf("22222\n");   int res=read(fp1,str,20);//从文件fp1中读放到字符数组str中if(res==0){break;}write(fp2,str,res);//从str写到文件fp2中}close(fp1);close(fp2);}if(filedir==NULL){break;}//文件夹读取到NULL结束}closedir(fd1);closedir(fd2);return 0;
}

2：有如下结构体 struct Student{

char name[20];

int age;

double math_score;

double chinese_score;

double english_score;

double physical_score;

double chemical_score;

double biological_score; } 申请一个该结构体数组，使用 fprintf / fscanf，将该结构体数组中的所有数据，写入文件中，然后重新加载到数组中同样的操作，使用fwrite/fread 和 write/read再做一遍

一：用fprintf和fscanf写

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/wait.h>
#include <pthread.h>
#define MAX 3
typedef struct student 
{char name[20];int age;double math_score;double chinese_score;double english_score;double physical_score;double chemical_score;double biological_score;
}s_student;
int main(int argc, const char *argv[])
{//定义结构体数组arrs_student arr[MAX]={{"陈丽",18,100,98,95,93,89,94},{"李华",20,72,84,68,79,94,99},{"张三",19,78,46,98,74,100,76}};FILE* fp=fopen("./student.txt","w");int i=0;while(i<MAX){fprintf(fp,"%s %d %.2lf %.2lf %.2lf %.2lf %.2lf %.2lf\n",arr[i].name,arr[i].age,arr[i].math_score,arr[i].chinese_score,arr[i].english_score,arr[i].physical_score,arr[i].chemical_score,arr[i].biological_score);i++;}fclose(fp);FILE* fp1=fopen("./student.txt","r");s_student arr2[MAX];int j=0;while(1){int res=fscanf(fp1,"%s %d %lf %lf %lf %lf %lf %lf\n",arr2[j].name,&arr2[j].age,&arr2[j].math_score,&arr2[j].chinese_score,&arr2[j].english_score,&arr2[j].physical_score,&arr2[j].chemical_score,&arr2[j].biological_score);if(res<0){break;}printf("%s %d %.2lf %.2lf %.2lf %.2lf %.2lf %.2lf\n",arr2[j].name,arr2[j].age,arr2[j].math_score,arr2[j].chinese_score,arr2[j].english_score,arr2[j].physical_score,arr2[j].chemical_score,arr2[j].biological_score);j++;}fclose(fp1);return 0;}

二：用read和write写

#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <unistd.h>  
#include <fcntl.h>  // 定义Student结构体  
struct Student {  char name[20];  int age;  double math_score;  double chinese_score;  double english_score;  double physical_score;  double chemical_score;  double biological_score;  
};  int main() {  // 定义并初始化一个Student结构体数组  struct Student students[3] = {  {"Alice", 20, 85.5, 90.0, 88.0, 75.0, 80.0, 82.0},  {"Bob", 21, 90.0, 85.0, 80.0, 70.0, 75.0, 77.0},  {"Charlie", 19, 80.0, 88.0, 75.0, 65.0, 70.0, 72.0}  };  // 打开文件用于写入  int fd = open("students.bin", O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);  if (fd == -1) {  perror("Error opening file for writing");  return EXIT_FAILURE;  }  // 将结构体数组写入文件  size_t size = sizeof(struct Student);  for (int i = 0; i < 3; i++) {  ssize_t written = write(fd, &students[i], size);  if (written != size) {  perror("Error writing to file");  close(fd);  return EXIT_FAILURE;  }  }  // 关闭文件  close(fd);  // 定义另一个Student结构体数组用于读取数据  struct Student new_students[3];  // 打开同一个文件用于读取  fd = open("students.bin", O_RDONLY);  if (fd == -1) {  perror("Error opening file for reading");  return EXIT_FAILURE;  }  // 从文件中读取数据到另一个结构体数组  for (int i = 0; i < 3; i++) {  ssize_t read_bytes = read(fd, &new_students[i], size);  if (read_bytes != size) {  perror("Error reading from file");  close(fd);  return EXIT_FAILURE;  }  }  // 关闭文件  close(fd);  // 打印读取的数据以验证  for (int i = 0; i < 3; i++) {  printf("Name: %s, Age: %d\n", new_students[i].name, new_students[i].age);  // 打印其他分数...  }  return 0;  
}

3：创建一对父进程，在父进程能够向子进程发送消息的基础上发同时子进程也能够向父进程发送消息

#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <unistd.h>  
#include <sys/types.h>  
#include <sys/wait.h>  #define BUFFER_SIZE 1024  int main() {  int fd_to_child[2]; // 父进程到子进程的管道  int fd_to_parent[2]; // 子进程到父进程的管道  pid_t pid;  char buffer[BUFFER_SIZE];  // 创建两个管道  if (pipe(fd_to_child) == -1 || pipe(fd_to_parent) == -1) {  perror("pipe");  exit(EXIT_FAILURE);  }  // 创建子进程  pid = fork();  if (pid == -1) {  perror("fork");  exit(EXIT_FAILURE);  }  if (pid == 0) { // 子进程  // 关闭父进程到子进程的写端和子进程到父进程的读端  close(fd_to_child[1]);  close(fd_to_parent[0]);  // 从父进程接收消息  read(fd_to_child[0], buffer, BUFFER_SIZE);  printf("Child received: %s\n", buffer);  // 向父进程发送消息  const char *msg_to_parent = "Hello from child!";  write(fd_to_parent[1], msg_to_parent, strlen(msg_to_parent) + 1);  // 关闭管道文件描述符  close(fd_to_child[0]);  close(fd_to_parent[1]);  exit(EXIT_SUCCESS);  } else { // 父进程  // 关闭父进程到子进程的读端和子进程到父进程的写端  close(fd_to_child[0]);  close(fd_to_parent[1]);  // 向子进程发送消息  const char *msg_to_child = "Hello from parent!";  write(fd_to_child[1], msg_to_child, strlen(msg_to_child) + 1);  // 从子进程接收消息  read(fd_to_parent[0], buffer, BUFFER_SIZE);  printf("Parent received: %s\n", buffer);  // 关闭管道文件描述符  close(fd_to_child[1]);  close(fd_to_parent[0]);  // 等待子进程结束  wait(NULL);  }  return 0;  
}