I am trying to prepare a database using C,which can store data and from which data can be retrieved and edited.
First storing,then retrieving data from the file works.But,during first run of the prog if choice#2(i.e.,DISPLAY)is entered without entering any data using choice#1(although the file contains data),then error occurs,gets hung.A part of the prog is shown:
#
include<stdio.h>
#include <string.h>
#include <conio.h>
#include <stdlib.h>typedef struct {
char name[30];
char company[50];
char address[200];
char pin[7];
char web[30];
}entry;
FILE *fpt;int menu(void);
entry *ptr,commodity;
int n=sizeof(entry);
void main()
{
int choice;
do
{
choice=menu();
switch(choice)
{
case 1:ptr=(entry *)malloc(sizeof(entry));
fpt=fopen("data4.bin","a");
printf("\nEnter the name of the commodity:");
scanf("%s",ptr->name);
printf("\nEnter the name of the producing company:");
scanf("%s",ptr->company);
printf("\nEnter the address of the producing company:");
scanf("%s",ptr->address);
printf("\nEnter the pincode:");
scanf("%s",ptr->pin);
printf("\nEnter the website of the producing company:");
scanf("%s",ptr->web);
fwrite(ptr,n,1,fpt);printf("ENTERED\n");
fclose(fpt);
continue;
case 2:fpt=fopen("data4.bin","r");
do
{
if (fread(&ptr->name, sizeof(ptr->name), 1, fpt) == 1 &&
fread(&ptr->company, sizeof(ptr->company), 1, fpt) == 1 &&
fread(&ptr->address, sizeof(ptr->address), 1, fpt) == 1 &&
fread(&ptr->pin, sizeof(ptr->pin), 1, fpt) == 1 &&
fread(&ptr->web, sizeof(ptr->web), 1, fpt) == 1)
{
printf("\n\nThe name of the commodity:");
printf("%s",ptr->name);
printf("\nThe name of the producing company:");
printf("%s",ptr->company);
printf("\nThe address of the producing company:");
printf("%s",ptr->address);
printf("\nPincode:");
printf("%s",ptr->pin);
printf("\nWebsite of the producing company:");
printf("%s",ptr->web);
}
else if (feof(fpt))
{
printf("\n\nfinished reading file!\n");
break;
}
else {
printf("an error occured while reading the file!\n");
break;
}
} while (1);
fclose(fpt);continue;
case 3:printf("\nThank You for using!");exit(1);
}
}while(choice==1||choice==2);
getch();
}
int menu(void)
{
int choice;
do{
printf("Enter your choice:\n");
printf("1.CREATE the linked list\n");
printf("2.DISPLAY\n");
printf("3.EXIT\n");
scanf("%d",&choice);
}while(choice!=1 && choice!=2 && choice!=3);
return(choice);
}Please suggest the cause of this error!