69.fprintf fscanf

• fprintf

  //从读文件中提取字符串到info1.user和info1.password中
  fscanf(pfr, "%s%s", info1.user, info1.password);

• fscanf

  //格式化写入到文件中
  fprintf(pfw, "%d %s %s
  ", i, info1.user, info1.password);

• printf 和 scanf是特例

  //从字符串中取出，键盘缓冲区
  fscanf(stdin, "a=%s", str);
  //int string映射到一 个字符串 显示器缓冲区
  fprintf(stdout, "%s", str);

完整代码:

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>

//创建结构体
typedef struct info7k7k
{
    char user[50];
    char password[50];

}INOF,* PINOF;

void main2x()
{
    //以读的方式打开文件
    FILE *pfr = fopen("7k7kOK.txt", "r");
    //以写的方式打开文件
    FILE *pfw = fopen("7k7kOKwithid.txt", "w");
    //编号
    int i = 0;
    //如果没到文件末尾
    while (!feof(pfr))
    {
        i++;
        //创建结构体
        INOF info1;
        //从读文件中提取字符串到info1.user和info1.password中
        fscanf(pfr, "%s%s", info1.user, info1.password);
        //格式化写入到文件中
        fprintf(pfw, "%d %s %s
", i, info1.user, info1.password);
    }
    //关闭文件
    fclose(pfr);
    fclose(pfw);
    system("pause");
}

void main3x()
{
    //int num = fprintf(stdout, "helloword%s","1234");
    //printf("
%d", num);//fprintf返回值就是写入成功字符的个数
    FILE *pf = fopen("C:\x.txt", "r");
    int num = fprintf(pf, "helloword%s", "1234");//写入失败返回-1
    printf("
%d", num);
    system("pause");
}

void main()
{
    //char str[128] = { 0 };
    //int numa;
    //int  numb;
    //int num = fscanf(stdin, "%s%d%d",str,&numa,&numb);
    ////返回值是扫描到几个数据,失败返回-1
    //printf("
%d", num);
    FILE *pf = fopen("C:\x.txt", "w");
    char str[128] = { 0 };
    int numa;
    int  numb;
    int num = fscanf(pf, "%s%d%d",str,&numa,&numb);
    printf("
%d", num);

    system("pause");
    
}