How to check whether ID already exists in File with C Programming - c

Question

I have this coding down below (just posting the Customers Management only).
This a database in which I am adding a customer each time it passes. Now I need to check whether the c.ID which is the client ID exists or not.
I tried doing a method called searchID which returns 1 if it's found or -1 if it's not found.
Problem is when I try to run the program, the program literally hangs there. Whether I press 23 or "ENTER" nothing happens and I would need to exit it using the CTRL + C;
so this is how it works:
When I add a customer (Which is a struct) it saves into the file but I first need to check
whether the ID exists in the database or not otherwise I need to ask the user to either input another ID or go back to the Main Menu
Any suggestions please?? thank you
#include<io.h>
#include<fcntl.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include "..\Headers\common.h"
#include "..\Headers\customerManagement.h"
static FILE *cfp;
static customer c;
#define STRUCTSIZE sizeof (customer)
/** This is the Customers's Main Menu in which the various sections can be
* accessed from here
*/
boolean customerMainMenu()
{
int optionC;
clrscr();
copyright();
printf ("\n\n\n\n\t\t ************* Customer's Main Menu *************\n \n \n");
printf ("Press [1] to add a new Customer\n");
printf ("Press [2] to edit a Customer\n");
printf ("Press [3] to list all Customers\n");
printf ("Press [4] to Show a Customer's last Order\n");
printf ("Press [5] to go back to Main Menu\n\n\n");
if (scanf ("%d",&optionC) == 1)
{
switch (optionC)
{
case 1:
{
clrscr();
getchar();
addCustomer();
break;
}
case 2:
{
printf ("Edit a Customer\n");
break;
}
case 3:
{
clrscr();
listCustomers();
getchar();
while (getchar()!='\n')
{
}
break;
}
case 4:
{
printf ("Customer's Last Order\n");
break;
}
case 5:
{
system ("PAUSE");
break;
}
default:
{
if (optionC != 1 || optionC != 2 || optionC != 3 || optionC != 4 || optionC !=5)
{
clrscr();
printf ("Invalid option!\n");
system ("PAUSE");
customerMainMenu();
}
break;
}
}
}
return TRUE;
}
/**
* This following method will append a customer to the
* database at the end of the file
*
* */
void addCustomer ()
{
char ch;
copyright();
printf ("\n\n\n\n\t\t ************* Add Client **********\n \n \n");
if ((cfp = fopen ("customers.dat","a+b")) == NULL)
{
fputs("Can't open customers.dat file\n",stderr);
}
printf ("\tThis will add another customer to the the database\n");
printf ("\tPress 'Y' to confirm or 'N' to return to the Client Main Menu\n\tWITHOUT adding a customer\n");
ch = getchar();
if (ch == 'n' || ch == 'N')
{
customerMainMenu();
}
else if (ch == 'y' || ch == 'Y')
{
clrscr();
printf ("\n\n\n\n\t\t ************* Add Client **********\n \n \n");
printf ("Please enter Name:\n");
while (scanf ("%s", c.name) == 0 || cCheck(c.name,100) == FALSE);
{
}
printf ("Please Enter Surname: \n");
while (scanf ("%s",c.surname) == 0 && cCheck (c.surname,100) == FALSE);
{
}
printf ("Please Enter ID Card, [NOTE! Only numbers are allowed!]\n");
int cID;
cID = 0;
while (scanf ("%d",&cID)==0)
{
printf ("Only Numbers are allowed!\n");
while (getchar() != '\n')
{
}
}
if (searchID(cID) == 1)
{
printf ("This ID already exists. Client already exists!\n");
printf ("Do you want to input another ID or return to Main Menu?\n");
printf ("Press 'Y' if you enter another ID, press any other key to return to Main Menu\n:");
ch = getchar();
if (ch == 'y' || ch == 'Y')
{
printf ("Enter another ID:\n");
while (scanf ("%d",&cID)==0)
{
printf ("Only Numbers are allowed!\n");
while (getchar() != '\n')
{
}
}
searchID(cID);
}
else if (searchID(cID) == -1)
{
cID = c.ID;
getchar();
}
}
while (getchar()!='\n')
{
}
printf ("Please Enter Address:\n");
gets(c.address);
fwrite (&c,STRUCTSIZE, 1, cfp);
printf ("For Testing purposes:\n");
printf (" %s\n %s\n %s\n %d\n", c.name, c.surname, c.address, c.ID);
askAnother();
}
else
{
printf ("\nInvalid choice! Either Y or N is accepted\n");
system ("PAUSE");
getchar();
addCustomer();
}
}
void listCustomers()
{
if ((cfp = fopen ("customers.dat","rb")) == NULL)
{
fputs("Can't open customers.dat file\n",stderr);
printf ("Returning to Customer Main Menu");
system ("PAUSE");
customerMainMenu();
}
rewind (cfp);
while (fread (&c,STRUCTSIZE,1,cfp)==1)
{
printf ("Customer: %s %s ID: %d\n", c.surname, c.name, c.ID);
}
fclose (cfp);
// system ("PAUSE");
}
void askAnother()
{
printf ("Do you want to add another Customer?\n");
printf ("Enter 'Y' for yes and 'N' to return to the Main Menu\n");
char input;
input = getchar();
if (input == 'Y' || input == 'y')
{
getchar();
addCustomer();
}
else if (input == 'N'|| input == 'n')
{
fclose (cfp);
customerMainMenu();
}
else
{
printf ("Invalid Option! Only Y or N are allowed\n");
system ("PAUSE");
askAnother();
}
}
boolean cCheck(char *test, int max)
{
int x;
for (x =0; x<max; x++)
{
if (isdigit(test[x]))
{
return FALSE;
}
if (x==max)
{
return TRUE;
}
x++;
}
return TRUE;
}
int fileSize()
{
int lengthOfFile;
int file;
file = open("Customers.dat",O_RDONLY,0);
lengthOfFile = lseek (file,0, SEEK_END);
return lengthOfFile;
}
int getNoOfRecords()
{
return (fileSize()/(STRUCTSIZE));
}
/**
* This method will compare the ID passed from the ID of the customer to check
* whether it is exists or not. If it exists it will output 1 otherwise it
* will output -1. This will make sure that the Person's ID is unique
*
*/
int searchID (int cID)
{
// for the while loop
int index;
index = 0;
//gets the number of records currently held in the file.
int records;
records = getNoOfRecords();
//User will input the ID into this variable and it will be checked
//whether it exists or not
int IDstatus;
IDstatus = 0;
while (index != records)
{
fread (&c,STRUCTSIZE,1,cfp);
if (c.ID == cID)
{
IDstatus = 1;
}
else
{
IDstatus = -1;
}
}
return IDstatus;
}
EDIT:
There are either 2 things:
Either the Method is not working the SearchID() method because even though I have 2 IDs which are 0 now, they are still accepting it
or else because of the c.ID which is staying 0.
When I'm inputting the data, it is accepting it BUT when I try to output the whole record, the Client ID stays 0.
Added to that, it IS letting me having Two IDs which are 0 so most probably the method is not working.... Thanks for all the help until now!

Answer 1

You missed to increment index, and of course you should exit the loop when you found the id:
while (index != records)
{
fread (&c,STRUCTSIZE,1,cfp);
if (c.ID == cID)
{
IDstatus = 1;
break; // <<<< otherwise IDStatus will be overwritten by next iteration
}
else
{
IDstatus = -1;
}
index++; // <<< otherwise endless loop
}