Why does the message print twice?

Question

I am creating a simple Tic Tac Toe for C, and here is a particular function which I am having a problem with. This is supposed to let the user select 'X' or 'O', and for the most art it works. However, if I enter a wrong symbol, it prints the statement: "Invalid symbol, please re-enter: " twice.

Why and how can I fix this?

char assign(void)                                 
{
      char user;

      printf("Would you like to be X or O (Enter your choice): ");
      user=getchar();
      while(user != 'X' && user != 'x' && user != 'O' && user != 'o')
      {
             printf("Invalid symbol, please re-enter: ");  
             user=getchar();
      }
      if(user == 'O' || user == 'o')        return('O');
      else if(user == 'X' || user == 'x')   return('X');     
}

Answer 1

The problem cause is related to the newline charachter

use scanf() in this way instead of using getchar()

scanf(" %c", &user);