I'm working through poker.c from King's C programming book and I need help analyzing it via gdb

He has the following:
Code:
 while (cards_read < NUM_CARDS) {
     bad_card = false;

     printf("Enter a card: ");

     rank_ch = getchar();
When gdb gets to rank_ch = getchar(), how do I pass a value (9s for 9 of spades for example) into gdb?

full source code: http://knking.com/books/c2/programs/poker.c