#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<ctype.h>
#define I 27
#define IR 25
#define File "test.txt"

struct customer
{
    long long identity;
    char iban[I];
    int money;
};

void filesave(struct customer cus)
{
    FILE *file;
    file = fopen(File,"a");
    if (file==NULL)
    {
        printf("the file did not open properly.");
    }

    fprintf(file,"%lld %s %d n",cus.identity,cus.iban,cus.money);

    fclose(file);
}

int identitycontrol(long long identity)
{
     int a=0,bas;
    long long i=1;
    while (a<11)
    {
        bas=(identity/i)%10;
        if (bas<0 || bas>9)
        {
            return 0;
        }
        
        i*=10;
        a++;
    }
    if (identity / i > 0 && identity>0) {
        return 0;
    }
    return 1;
}

int ibancontrol(char iban[I])
{
     if(!isalpha(iban[0]) || !isalpha(iban[1]))
     {
        return 0;
     }
     
    for (int i = 2; i < I; i++)
    {
        if (iban[i]<48 || iban[i]>57)
        {
            return 0;
        }
        
    }
    return 1;
}

int moneycontrol(int money)
{
    if (money>0)
    {
        return 1;
    }
    return 0;
}

int transfermoneycontrol(int b, int m)
{
    if(b>=m)
        return 1;
     else
        return 0;
}

int moneyorder(char account1[],char account2[],int transfermoney)
{
    FILE *file;
    file = fopen(File,"r");
    struct customer cus[100];
    char temp[100];
    int y=0,s=0;
    while ( fgets(temp,100, file) != NULL )
    {
            sscanf(temp,"%lld %s %d",&cus[s].identity,cus[s].iban,&cus[s].money);
    
        // printf("%d",strlen(cus[s].iban));
        if(strcmp(cus[s].iban,account1)==0)
        {
                cus[s].money -=transfermoney;  
                y++;

        }
        if(strcmp(cus[s].iban,account2)==0)
        {
            cus[s].money +=transfermoney;
            y++;
        }
        s++;
    }    
        printf("%sn",account1);
        printf("%sn",cus[0].iban);

     for(int z=0;z<s;z++)
    {
        printf("nGuncel bilgiler:n");
        printf("%d: %s  %lld  %d n",z+1,cus[z].iban,cus[z].identity,cus[z].money);
    }
    
    fclose(file);

    

   
    
    file = fopen(File, "w");
    if (file == NULL)
    {
        printf("the file did not open properly.");
        return 0;
    }
    
    for (int x = 0; x < s; x++)
    {
       filesave(cus[x]);
    }
    fclose(file);
    return  1;
}

int main()
{
    int choice=0,control=0;
    struct customer cus;
    char account1[I];
    char account2[I];
    int transfermoney;
   
    
    while (1)
    { 

    printf("-----Menü-----n");
    printf("1:Entryn");
    printf("2:Transfern");
    printf("3:Exitn");

    printf("What is your choice: ");
    scanf("%d",&choice); 
    fflush(stdin);
    switch (choice)
    {
    case 1:
        while (1)
        {   
                printf("Please enter your identity: ");
                scanf("%lld",&cus.identity);
                fflush(stdin);
                if (identitycontrol(cus.identity)==1)
                {
                    
                break;
                }   
        }
        while (1)
        {
                printf("Please enter your iban: ");
                scanf("%s",cus.iban);
                //fgets(cus.iban,I,stdin);
                //cus.iban[strlen(cus.iban)-1]='';                
                fflush(stdin);
                if (ibancontrol(cus.iban)==1)
                {
                    
                    break;
                }
        }
        
        while (1)
        {
                printf("Please enter your money: ");

                scanf("%d",&cus.money);
                fflush(stdin);
                if (moneycontrol(cus.money)==1)
                {
                    break;
                }    
        }     
                filesave(cus);
        break;
        case 2 :
        while(1)
        {
                printf("Please enter the main account we will send money to: ");
                fflush(stdin);
              //  fgets(account1,I,stdin);
               // account1[strlen(account1)-1]='';
                scanf("%30s",account1);
              fflush(stdin);
            // getchar();
               if (ibancontrol(account1)==1)
               {
                   break;
               }
                      
        }
        while(1)
        {
                printf("Please enter the account from which you will receive money: ");
                //fgets(account2,I,stdin);  
                scanf("%30s",account2);
               fflush(stdin);
             //getchar();
                if (ibancontrol(account2)==1)
                { 
                    break;
                }  
        }        
        
       while(1)
        {
                printf("Please enter your transfer money: ");
                scanf("%d",&transfermoney);
                fflush(stdin);
                if (moneycontrol(transfermoney)==1)
                {
                   break;
                }          
        }
                
                int a=moneyorder(account1,account2,transfermoney);
            if (a==1)
            {
                printf("Money order sucsessful.n");
            }
            else if (a==0)
            {
                printf("Money order unsucsessful.n");
            }
            


            
            break;
        case 3:
                exit(2);
        break;
    default:
                printf("Wrong choice!!n");
        break;
    }
   
}
 return 0;



}

After getting the account1 variable, I can print it, but when it enters the world containing account 2, account1 disappears, but I don’t know why.All the remaining functions and file operations are working, but there is a problem in that part.account1 disappears, I cannot press it in a way that I do not understand or the function. When I send it, it’s empty inside, just n