How to prevent non-integer input in c? [duplicate]

I am trying to run a program whereby user can only enter 1 or 2. If the user enters any other numbers or alphabets, it should prompt the user back to entering input again. I have tried the following code and it works if user enter an integer which is not 1 or 2, but the whole program will go haywire if entered any alphabets. I tried to validate with

if == 0 but doesnt work as well. Does anyone have any idea?

int getUserInput(){

printf("1: You have chosen 1.\n");
printf("2: You have chosen 2.\n\n");

printf("Enter an option: ");
scanf("%d", &userSel);

if(userSel!= 1 && userSel!= 2){
    
    printf("You have entered an invalid input. Please try again.\n");
    getUserInput();
}
else{
    printf("Enter a number: ");
    scanf("%d", &userNo);
}

printf("userSelection: %d\n", userSel);
printf("1userNumber: %d\n", userNo);

return 0; 
}