C语言以数据块的形式读写文件实例代码

size_t fread ( void *ptr, size_t size, size_t count, FILE *fp );

size_t fwrite ( void * ptr, size_t size, size_t count, FILE *fp );

#include<stdio.h>
#define N 5
int main(){
  //从键盘输入的数据放入a，从文件读取的数据放入b
  int a[N], b[N];
  int i, size = sizeof(int);
  FILE *fp;
  if( (fp=fopen("D:\\demo.txt", "rb+")) == NULL ){
    printf("Cannot open file, press any key to exit!\n");
    getch();
    exit(1);
  }
 
  //从键盘输入数据 并保存到数组a
  for(i=0; i<N; i++){
    scanf("%d", &a[i]);
  }
  //将数组a的内容写入到文件
  fwrite(a, size, N, fp);
  //将文件中的位置指针重新定位到文件开头
  rewind(fp);
  //从文件读取内容并保存到数组b
  fread(b, size, N, fp);
  //在屏幕上显示数组b的内容
  for(i=0; i<N; i++){
    printf("%d ", b[i]);
  }
  printf("\n");
  fclose(fp);
  return 0;
}

#include<stdio.h>
#define N 2
struct stu{
  char name[10]; //姓名
  int num; //学号
  int age; //年龄
  float score; //成绩
}boya[N], boyb[N], *pa, *pb;
int main(){
  FILE *fp;
  int i;
  pa = boya;
  pb = boyb;
  if( (fp=fopen("d:\\demo.txt", "wb+")) == NULL ){
    printf("Cannot open file, press any key to exit!\n");
    getch();
    exit(1);
  }
  //从键盘输入数据
  printf("Input data:\n");
  for(i=0; i<N; i++,pa++){
    scanf("%s %d %d %f",pa->name, &pa->num,&pa->age, &pa->score);
  }
  //将数组 boya 的数据写入文件
  fwrite(boya, sizeof(struct stu), N, fp);
  //将文件指针重置到文件开头
  rewind(fp);
  //从文件读取数据并保存到数据 boyb
  fread(boyb, sizeof(struct stu), N, fp);
  //输出数组 boyb 中的数据
  for(i=0; i<N; i++,pb++){
    printf("%s %d %d %f\n", pb->name, pb->num, pb->age, pb->score);
  }
  fclose(fp);
  return 0;
}