Kак проверить есть ли в массиве уже введенныe ранее юзером данные

#include <stdio.h>
#include <string.h>
struct test
{
    float donation, total_donation;
    char name[10], surname[10], year_of_birth[4], sex[2];
    int pasport;
} users[200];

char secret_code_for_admin[10] = "adad";
char secret_name_for_admin[10] = "11a11";
int current_number_of_users = 0;


void retrial_login_for_user()
{
    int user_name;
    printf("User name: "); // if user will want to enter into the system he can enter with his pasport
    scanf("%d", &user_name);
    for (int i; i < 200; i++)
    {
        if (user_name == users[i].pasport)
        {
            printf("welcome back!");
        }
        else
            printf("mistake");
    }
}
void personal_information_of_user()
{
    char reading_the_user_answer[10];
    printf("To donate let us some following information\n");
    printf("Name: ");
    scanf("%s", users[current_number_of_users].name);
    printf("Your surname: ");
    scanf("%s", users[current_number_of_users].surname);
    printf("Year of birth: ");
    scanf("%s", users[current_number_of_users].year_of_birth);
    printf("Your sex: ");
    scanf("%s", users[current_number_of_users].sex);
    printf("Your pasport: ");
    scanf("%d", &users[current_number_of_users].pasport);
    printf("Your donation is: ");
    scanf("%f", &users[current_number_of_users].donation);
    users[current_number_of_users].total_donation = users[current_number_of_users].donation - ((users[current_number_of_users].donation / 100) * 10);
    printf("**************************************************************\n");
    printf("The total sum of your donation with the included tax is: %.2f\n", users[current_number_of_users].total_donation);
    printf("**************************************************************\n");
    current_number_of_users++;
    printf("Do you want to login in system?\nYes/no: ");
    scanf("%s", reading_the_user_answer);
    if (strcmp(reading_the_user_answer, "yes") == 0)
    {
        retrial_login_for_user();
    }
}

void user_access()
{
    int user_name;
    char action_of_user[10];
    printf("\nYou loged in as an User.\nYou have two avalable options\n");
    printf("***************************************************************\n");
    printf("                    Donate or Login\n");
    printf("***************************************************************\n");
    printf("\nPlease make your choose by starting with a small letter:\n ");
    scanf("%s", action_of_user);
    if (strcmp(action_of_user, "donate") == 0)
    {

        personal_information_of_user();
    }
    if (strcmp(action_of_user, "login") == 0)
    {
        retrial_login_for_user();
    }
}

void admin_access()
{
    char choose_of_admin[20];
    char pass_admin[10];
    char pass_name_admine[10];
    printf("User name: ");
    scanf("%s", pass_admin);

    while (strcmp(pass_admin, secret_code_for_admin))
    {
        printf("\nWrong Username.\nTry again: ");
        scanf("%s", pass_admin);
    }

    printf("User name is correct.\n");
    printf("Password: ");
    scanf("%s", pass_name_admine);
    while (strcmp(pass_name_admine, secret_name_for_admin))
    {
        printf("\nWrong password.\nTry again: ");
        scanf("%s", secret_name_for_admin);
    }
    printf("***************************************************************\n");
    printf("               All available options.\n");
    printf("***************************************************************\n");
    printf("View\nSearch\nDelete\nNotify\nEcoGift\nEcoCheck\nSort\nExit\n");
    printf("\nPlease make your choose with a lowecase letter: ");
    scanf("%s", choose_of_admin);
    if (strcmp(choose_of_admin, "view") == 0)
    {
        printf("hi there");
    }
}
int main()

{

    char password_for_user[10];

    char admin_or_user[10];
    do
    {
        printf("Admin or user: ");
        scanf("%s", admin_or_user);

    } while (strcmp(admin_or_user, "admin") && strcmp(admin_or_user, "user"));
    {

        if (strcmp(admin_or_user, "admin") == 0)
        {
            admin_access();
        }

        if ((strcmp(admin_or_user, "user") == 0))
        {
            user_access();
        }
    }
}

Как проверить уже введенные юзером данные. В данном случае я пытаюсь проверить с помощью цикла, если ранее введенный паспорт (которуй используется как User Name) совпадает с тем, что вводит пользователь, но код дальше if (user_name == users[i].pasport) не работает.