d&d dice rolling.

roll.c

#include <fcntl.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int roll_dice(int, int);

int main(int argc, char const *argv[]) {
  // Open the random file.
  int dev_urandom;
  if ((dev_urandom = open("/dev/urandom", O_RDONLY)) < 0) {
    perror("opening /dev/urandom");
    exit(1);
  }

  int grand_total = 0;
  for (int i = 1; i < argc; i++) {
    int num_dice = 0;
    int sides = 0;
    sscanf(argv[i], "%dd%d", &num_dice, &sides);

    if (num_dice == 0 || sides == 0) {
      fprintf(stderr, "Bad dice roll string.\n");
      continue;
    }

    int total = 0;
    int rolls[num_dice];

    for (int j = 0; j < num_dice; j++) {
      rolls[j] = roll_dice(dev_urandom, sides);
      total += rolls[j];
      grand_total += rolls[j];
    }

    if (num_dice > 1) {
      printf("%d (", total);
      for (int j = 0; j < num_dice; j++) {
        if (j == num_dice - 1) {
          printf("%d", rolls[j]);
        } else {
          printf("%d ", rolls[j]);
        }
      }
      printf(")\n");
    } else {
      printf("%d\n", total);
    }
  }

  if (argc > 2) {
    printf("%d in total.\n", grand_total);
  }

  // Close the files.
  close(dev_urandom);
}

int roll_dice(int file, int sides) {
  unsigned char random;
  read(file, &random, sizeof(random));
  return random % sides + 1;
}

nixpulvis at snowcone in ~ 
$ roll 2d6 5d8
6 (1 5)
31 (6 5 8 5 7)
37 in total.