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\n", 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[];
     char password[];

 }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 = ;
     //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\n", 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("\n%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", "");//写入失败返回-1
     printf("\n%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("\n%d", num);
     FILE *pf = fopen("C:\\x.txt", "w");
     char str[] = {  };
     int numa;
     int  numb;
     int num = fscanf(pf, "%s%d%d",str,&numa,&numb);
     printf("\n%d", num);

     system("pause");

 }