c 文件操作

 

 

 

 

#include <stdio.h>
#include <stdlib.h>  // 添加exit函数的头文件void demo01()
{FILE* fp;char ch, FileName[20];printf("请输入所用的文件名：");//scanf_s("%s", FileName, (unsigned)_countof(FileName));  // scanf_s需要指定缓冲区大小\//**将scanf换成scanf_s
但是，scanf_s函数只能在vs上使用，其他平台无法使用，故修改后代码无法移植，不建议*/scanf("%s", FileName);/*if ((fp = fopen_s(FileName, 'w')) == NULL){printf("无法打开此数据文件、\n");exit(0);}*/// 修正fopen_s的使用if (fopen_s(&fp, FileName, "w") != 0)  // fopen_s正确用法{printf("无法打开此数据文件\n");exit(0);}ch = getchar();printf("请和收入字符串（一# 结束）:");ch = getchar();while (ch != '#'){fputc(ch, fp);putchar(ch);ch = getchar();}fclose(fp);// putchar(10);
}void demo02()
{FILE* fp;char str[1024];fp = fopen("demo.txt", "r");if (fp == NULL)printf("打开文件失败");elseprintf("打开文件成功");while (!feof(fp)){// printf("大小:%d", sizeof(str));if (fgets(str, sizeof(str), fp) != NULL)printf("\n 读取文件数据如下:\n %s", str);}}struct student
{int no;char name[10];
};void demo03()
{struct student st[2] = {{101,"张三"},{102,"李四"}};FILE* fp = fopen(".\\studentdata.txt", "w");if (fp == NULL){perror("open file fail\n");exit(1);}fwrite(st, sizeof(struct student), 2, fp);fclose(fp);}void demo04()
{FILE* fp = fopen(".\\studentdata.txt", "r");if (fp == NULL){perror("open file fail\n");exit(1);}struct student st[2];fread(st,sizeof(struct student), 2,fp);printf("No:%d \t Name:%s\n", st[0].no, st[0].name);printf("No:%d \t Name:%s\n", st[1].no, st[1].name);//int i;for (int  i = 0; i < 2; i++){printf("%d\n", i);printf("No:%d \t Name:%s\n", st[i].no, st[i].name);}fclose(fp);}void demo05()
{FILE* fpold, * fpnew;fpold = fopen("old.dat", "r");fpnew = fopen("new.dat", "w");// 检查文件是否成功打开if (fpold == NULL || fpnew == NULL) {printf("文件打开失败！\n");exit(1);}/*while (!feof(fpold))putchar(getc(fpold));*/int ch;  // 使用 int 类型，因为 EOF 是 int 类型while ((ch = getc(fpold)) != EOF) {putchar(ch);}printf("\n");// rewind(!feof(fpold));/*rewind(!feof(fpold)) 错误!feof(fpold) 返回的是布尔值（0或1），而不是文件指针应该直接使用 rewind(fpold)**/rewind(fpold);/*while (!feof(fpold))putc(getc(fpold), fpnew);*/while ((ch = getc(fpold)) != EOF) {putc(ch, fpnew);}fclose(fpold);fclose(fpnew);}
int main()
{demo05();return 0;
}