Existing field in struct to be overwritten. BINARY FILES.

[wacky_jay]

Hi guys. I'm having trouble with overwriting a specific field in my struct. Anyone can help me? What should I do? Please help.

void Deposit(FILE *fp, struct information info, char set[]){
     int x, flag;
     float deposit;
     char id[8];
     fp=fopen("account.dat","a+b");
     system("cls");
     printf("=========DEPOSIT=========");
     printf("\nEnter Account ID:(XX-XXX)");
     gotoxy(18,1);scanf("%6s",id);
     flag=0;
     if (id[2]!='-' || strspn(id,set)!=6)
         { /*format*/
           flag=1;
           system("cls");
           printf("Invalid Account# format! ");
           printf("\nPress any key to continue..");
           getch();
         } /*format*/
     
     if (flag==0)
     {
      while(fread(&info, sizeof(struct information), 1, fp) != NULL)
         {
           if(strcmp(id,info.id)==0)
          {
            system("cls");
            printf("Account# found!");
            printf("\nPress any key to continue..");
            flag=2;
            getch();
          } 
         }
     }
     if (flag==2)
     {
      system("cls");
      printf("\nEnter deposit amount: ");
      scanf("%f", &deposit);
      if (deposit <= 0)
      {
       printf("\nInvalid amount.");
       getch();
      }
      else
      {
      info.obalance+=deposit;
      fwrite(&info,sizeof(struct information),1,fp);
      }
                                    
      getch();
     }
     fclose(fp);
}

[jimblumberg]

When you open your file with the "a+" file open mode you can only write to the end of the file. You may want to study the documentation for fopen() and use a mode that allows you to write anywhere in the file.

Jim

[wacky_jay]

so any suggestion?

[jimblumberg]

Yes, study the documentation and pick a mode that lets you write anywhere in the file.

Jim

[qny]

You might want to read the documentation for fseek().