Reading a character with scanf ()

Question

This code is for craps .

#include <stdio.h> #include <stdlib.h> #include <stdbool.h> #include <time.h> int roll_dice(void); bool play_game(void); int main() { int i, ch,win = 0,lose = 0; bool flag; srand((unsigned)time(NULL)); do { flag = play_game(); if(flag) { printf("You win!"); win++; } else { printf("You lose!"); lose++; } printf("\n\nPlay again(Y/N)? "); scanf("%c", &ch); ch = getchar(); printf("\n"); }while(ch == 'Y' || ch == 'y'); printf("\nWins: %d Losses: %d",win,lose); return 0; } int roll_dice(void) { return rand()%6 + rand()%6 + 2; } bool play_game(void) { int sum = roll_dice(); printf("You rolled: %d\n", sum); if(sum == 7 || sum == 11) return 1; else if(sum == 2 || sum == 3 || sum == 12) return 0; else { int point = sum; printf("Your point is: %d\n", point); do { sum = roll_dice(); printf("You rolled: %d\n", sum); if(sum == 7) return 0; }while(point != sum); return 1; } } 

I only have a problem with a code snippet

  printf("\n\nPlay again(Y/N)? "); scanf("%c", &ch); ch = getchar(); printf("\n"); 

I used because it ends after one iteration with any user input Y or N I thought I was doing it wrong by placing ch = getchar() to eat \n , I deleted it and put a space in front of the conversion specifier and replaced it with " %c" , which also didn't work. When I replaced the conversion specifier with %d works fine.
Is there something wrong with this? I visited this post and it says the same thing as me.

Answer 1

The marked code has undefined behavior, since ch is of type int , and the %c format specifier must match char .

When I replaced the conversion specifier% d, it works fine.

When you switch to %d , scanf() crashes because Y or Y not int , so no input is consumed (except for the leading space, which discards the new line character during subsequent iterations of the loop), and the subsequent ch = getchar() actually reads the character entered by the user, and the code works with fluke. Always check the return value of scanf() , which returns the number of jobs completed.

Answer 2

 scanf("%c", &ch); ch = getchar(); 

And how did you lose the previous char stored in ch . What about

 ch = fgetc(stdin); while (fgetc(stdin) != '\n') ; 

instead

Answer 3

You convert a character with scanf () and then overwrite it with getchar () immediately afterwards. I would not expect it to work if you did not type "yy" before entering ENTER, but then your second confirmation will fail.

BTW, use the space in " %c" .

Answer 4

 printf("Play again? "); scanf(" %c", &char); 

this code works for me. The project is made from the book of K.N. King "With programming: a modern approach." I have encountered this problem before and had the same problem. On page 224 there is an example guess.c project that includes the exact same “ask” (“play again”) command. And the author used scanf ("% c", & command); (he used the command instead of ch) and it worked. I remember using it during the dice project, but that didn't work. I guess I missed something. In general, an expression above 100% works.