记录文件功能的添加/显示/删除不起作用

Question

问题的标题很好地解释了这种情况。我不习惯使用文件和相关命令（例如 fseek、fwrite 等）。

无论如何，以下程序必须模拟一个菜单，并为用户提供添加、编辑、删除或显示文件记录的选择。这是一个相当简单的任务，但我无法弄清楚我做错了什么。

 #include <stdio.h>


typedef struct{
 int code;
 char description[100];
 int volume;
}product;



int main() {



int pick =0, i;
product *p;
FILE *filePtr;

void add(FILE *filePtr, product* p);
void removal(FILE *filePtr, product* p);
void show(FILE *filePtr, product* p);
void edit(FILE *filePtr, product* p);
void description(FILE *filePtr, product* p);


if ( ( filePtr = fopen( "stock.dat", "rb+")) == NULL ) {
    printf("The file could not be read");
}
else {


do{
   printf("    ************ MAIN MENU ************\n");
   printf("  ** -------------welcome------------- **\n");
   printf(" **                                      ** \n");
   printf("*  Please select one of the commands below *\n");
   printf("********************************************\n");
   printf("* Press 1 to remove products from the list *\n");
   printf("* Press 2 to change a product's quantity   *\n");
   printf("* Press 3 to add a new product to the list *\n");
   printf("* Press 4 to view product list             *\n");
   printf("* Press 5 to exit the programm             *\n");
   printf("********************************************\n");
   scanf("%d", &pick);

   switch ( pick ) {

   case 1:
      removal(filePtr, p);
    break;

   case 2:
      edit(filePtr, p);
    break;

   case 3:
     add(filePtr, p);
   break;

   case 4:
     show(filePtr, p);
   break;





   default:
      printf("Error! Please enter a correct number");
   break;
 }
 }while (pick != 5);

  }




fclose(filePtr);


return 0;
}


void removal(FILE *fileptr, product * p) {
    int code;


    product empty = { 0, " ", 0 };

    printf("\n\nYou are about to delete a record, please enter the product's code");
    scanf("%d", &code);

    fseek( fileptr, (code - 1) * sizeof(p), SEEK_SET);
    fread( &p->code, sizeof(p), 1, fileptr);

    if (p->code == 0){
        printf("Product code not found, please retry");
    } else {
        fseek( fileptr, (code -1) * sizeof(p), SEEK_SET);

        fwrite( &empty, sizeof(p), 1, fileptr);

        printf("Code was found, product removed successfully\n\n");
    }
}

 void add(FILE *fileptr, product * p){

  int code, quantity;

  printf("You are about to add a new product in the list\n Please input the product's code\n");

  scanf("%d", &code);


  fseek( fileptr, (code-1) * sizeof(p), SEEK_SET);
  fread(&code, sizeof(p), 1, fileptr);


    fseek(fileptr, (code-1) * sizeof(p), SEEK_SET);
    fwrite( &code, sizeof(p), 1, fileptr);

    printf("Now enter the product's remaining quantity");
    scanf("%d", &quantity);

    fseek(fileptr, (quantity-1) * sizeof(p), SEEK_SET);
    fwrite( &quantity, sizeof(p), 1, fileptr);





 }


 void edit(FILE *fileptr, product * p){

  int code, volume;

  printf("\nYou are about to edit a existing product's quantity\n Please enter the product's code\n");
  scanf("%d", &code);

  fseek(fileptr, (code -1) * sizeof(p), SEEK_SET);
  fread(&code, sizeof(p), 1, fileptr);

  if (p->code == 0){
    printf("\nThe code you entered is not in the list, please retry\n");
  }else{
    printf("\nCode found!\n Product's  current quantity is %d", &p->volume);
    printf("\n Please enter the new quantity");
    scanf("%d", &volume);

    p->volume = volume;


    fseek(fileptr, (volume -1) * sizeof(p), SEEK_SET);
    fwrite(&volume, sizeof(p), 1, fileptr);

    }


 }


void show(FILE *fileptr, product * p){

 int i=1;


 printf("\n\n\n               ****SHOWING ALL PRODUCTS****\n\n\n");
 printf("PRODUCT CODE      QUANTITY IN STOCK\n");



 while (i<100 && !feof(fileptr)){
    fscanf( fileptr, "%d%d", &p->code, &p->volume);
    printf("%d            %d\n", &p->code, &p->volume);
    fseek(fileptr, (p->code + 1) * sizeof(p), SEEK_SET);
    fscanf( fileptr, "%d%d", &p->code, &p->volume);
    i++;
   }
 printf("You may scroll back up to view the list\n\n");

 }

为了了解正在发生的事情：如果用户输入选项 4，程序不会显示任何记录，而是显示随机值，但即使用户选择添加产品（通过选择选项 3，即add 函数），以后不会显示，因此即使用户选择删除也不能删除。同样，我在编程方面相当陌生（我相信你经常听到这个：P）。我之前也发过类似的问题，但没有得到解决方案。

编辑 我编辑了大部分代码，基本上文件以二进制形式打开，现在结构产品 p 传递给每个函数。现在据说问题已解决，程序运行一次显示正确的值和记录，但由于未知原因自行崩溃。任何额外的帮助都会很棒

Answer 1

你的show函数肯定有问题...

对于初学者，对其进行以下更改（使用注释标记）：

void show(FILE *fileptr){

    typedef struct{
        int code;
        char description[100];
        int volume;
    } product;

    product p;

    int i=1;

    // removed the re-opening of the file


    printf("\n\n\n               ****SHOWING ALL PRODUCTS****\n\n\n");
    printf("PRODUCT CODE      QUANTITY IN STOCK\n");

    // moved the first fscanf() into the while loop
    while (i<100 && !feof(fileptr)){
        fscanf( fileptr, "%d%d", &p.code, &p.volume);
        printf("%d            %d\n", &p.code, &p.volume);
        fseek(fileptr, (p.code + 1) * sizeof(p), SEEK_SET);
        i++;
    }
    printf("You may scroll back up to view the list\n\n");

}