似乎无法将输入与文本文件中的值匹配

Question

这是 items.txt 包含的内容:

275,Fresh Fish,12.34,0
386,Soft kleenex,45.67,1
240,Ultra Tide,24.34,1
916,Red Apples,123.45,0
385,Magic Broom,456.78,1
495,Liquid Soap,546.02,1
316,Chocolate Cookies,78.34,1
355,Organic Milk,24.34,0
846,Dark Chocolate,123.45,1
359,Organic Banana,99.99,0

当用户输入“Y”时如何倒回文件？如果我第一次输入正确的值，它就会起作用。

#include <stdio.h>
#define TAX (0.13)
void keybFlush(){
   while(getchar() != '\n');
}
int getInt(){
   int val;
   char nl = 'x';
   while (nl != '\n'){
      scanf("%d%c", &val, &nl);
      if (nl != '\n'){
         keybFlush();
         printf("Invalid Integer, please try again: ");
      }
   }
   return val;
}
int yes(){
   char ch = 'x';
   int res;
   do{
      ch = getchar();
      res = (ch == 'Y' || ch == 'y');
      keybFlush();
   } while (ch != 'y' && ch != 'Y' && ch != 'n' && ch != 'N' && printf("Only (Y)es or (N)o are acceptable: "));
   return res;
}
int main(){
   int upc, userUpc, found = 0;
   double price;
   int isTaxed, i;
   char item[21], ch, x, y;
   FILE* fptr = fopen("items.txt", "r");
   if (fptr){
   do {
   userUpc=getInt();
printf(" UPC  | Name               |   Price   |   Tax   |   Total\n"
       " -----+--------------------+-----------+---------+-----------\n");
   printf("its : %d\n", userUpc);
   while (!feof(fptr)){
      fscanf(fptr, "%d,%[^,],%lf,%d", &upc, item, &price, &isTaxed);
      if ( upc == userUpc){
         if(!feof(fptr)){
            printf("%-6d|%-20s|%11.2lf|", upc, item, price);
            if (isTaxed)
               printf("%9.2lf|%11.2lf\n", price * TAX, price * (1+TAX));
            else
               printf("%9.2lf|%11.2lf\n", 0.0, price);
            found = 1;
         }
      }
   }
   if (!found){
      printf("Can't find any matched records\n");
   }
   printf("Do you want to continue: ");
   i=yes();  // if yes, rewind the file
   } while (!userUpc || (i == 1));
   fclose(fptr);

   }
   else{
      printf("could not open the file\n");
   }
   return 0;
}

如果我输入“y”继续并输入正确的值，它似乎无法正确输出。

Answer 1

要将文件光标的位置更改为文件开头:

fseek(filePtr, 0, SEEK_SET);

有关文件操作的更多信息: http://www.gnu.org/software/libc/manual/html_node/File-Positioning.html