c - 如何从文本文件中读取和保存数据？

Question

我需要帮助了解如何将数据保存到变量中。如果我有 100 行数据怎么办？那我可能需要100个变量？请让我了解如何解决这个问题。非常感谢!

void show_addon(){
   FILE *afp; //pointer for addon text file
   char text_file[250];

   afp = fopen("addon.txt", "r"); //opens txt file and READS only

   puts("----------------------------------------------------");
   puts(" --------------------ADD-ONS----------------------- ");
   puts("----------------------------------------------------");

   // printf("%s\n", text_file );
   fscanf(afp, "%5[^:]:%[^:]:%f:%[^\n]\n", addon1.code, addon1.name, &addon1.price, addon1.description);
   fscanf(afp, "%5[^:]:%[^:]:%f:%[^\n]\n", addon2.code, addon2.name, &addon2.price, addon2.description);
   fscanf(afp, "%5[^:]:%[^:]:%f:%[^\n]\n", addon3.code, addon3.name, &addon3.price, addon3.description);
   fscanf(afp, "%5[^:]:%[^:]:%f:%[^\n]\n", addon4.code, addon4.name, &addon4.price, addon4.description);
   fscanf(afp, "%5[^:]:%[^:]:%f:%[^\n]\n", addon5.code, addon5.name, &addon5.price, addon5.description);

   if ((afp = fopen("addon.txt", "r"))== NULL)
   {
       puts("File could not be found");
    } else {     
       printf("Code  : %s\n",addon1.code);
       printf("Name     : %s\n",addon1.name);
       printf("Price    : RM %.2f\n",addon1.price);
       printf("Description    : %s\n",addon1.description);
       printf("---------------------------------------\n");
       printf("Code  : %s\n",addon2.code);
       printf("Name     : %s\n",addon2.name);
       printf("Price    : RM %.2f\n",addon2.price);
       printf("Description    : %s\n",addon2.description);
       printf("---------------------------------------\n");   
       printf("Code  : %s\n",addon3.code);
       printf("Name     : %s\n",addon3.name);
       printf("Price    : RM %.2f\n",addon3.price);
       printf("Description    : %s\n",addon3.description);
       printf("---------------------------------------\n");
       printf("Code  : %s\n",addon4.code);
       printf("Name     : %s\n",addon4.name);
       printf("Price    : RM %.2f\n",addon4.price);
       printf("Description    : %s\n",addon4.description);
       printf("---------------------------------------\n");
       printf("Code  : %s\n",addon5.code);
       printf("Name     : %s\n",addon5.name);
       printf("Price    : RM %.2f\n",addon5.price);
       printf("Description    : %s\n",addon5.description);
    }  
   puts("------------------------------------------------------------------------------");

   fclose(afp); //close txt file
   return 0;
}

Answer 1

What if I had a data of 100 lines? Then I might need 100 variables?

不，您将使用数组来保存数据并使用 while 循环来读取数据。

类似于:

ADDON_TYPE addon[100];
int j;
if (!(afp = fopen("addon.txt", "r"))
{
    printf("File error\n");
    exit(1);
}

j = 0;
while (j < 100 && 
       4 == fscanf(afp, 
                   "%5[^:]:%[^:]:%f:%[^\n]\n", 
                   addon[j].code, 
                   addon[j].name, 
                   &addon[j].price, 
                   addon[j].description))
{
    ++j;
}

要打印值，您可以使用for循环。像这样的东西:

int i;
for(i = 0; i<j; ++i)
{
   printf("Code  : %s\n",addon[i].code);
   printf("Name     : %s\n",addon[i].name);
   printf("Price    : RM %.2f\n",addon[i].price);
   printf("Description    : %s\n",addon[i].description);
   printf("---------------------------------------\n");
}

在许多情况下，您会使用动态数组(即使用 malloc 创建)，以便在文件包含的条目数超过到目前为止已分配。

顺便说一句:在您的代码中，第二个 fopen 很奇怪 - 似乎是再次打开文件的错误