roll-dice

Roll Dice

When to use this skill

Use this skill when the user needs to:

• Roll a single die (d6, d20, etc.)
• Roll multiple dice (2d6, 4d8, etc.)
• Roll with modifiers (d20+5, 2d6-1)
• Generate random numbers for games or decisions

Rolling a Single Die

Generate a random number from 1 to the given number of sides:

# Bash (macOS/Linux)
echo $((RANDOM % <sides> + 1))

# PowerShell (Windows)
Get-Random -Minimum 1 -Maximum (<sides> + 1)

# Python (more precise for large numbers)
import random
print(random.randint(1, <sides>))

Replace <sides> with the number of sides on the die (e.g., 6 for a standard die, 20 for a d20).

Common Dice Types

Notation	Sides	Common Use
d4	4	Small damage rolls
d6	6	Standard die, ability scores
d8	8	Weapon damage
d10	10	Percentile rolls (paired)
d12	12	Greataxe damage
d20	20	Attack rolls, skill checks, saving throws
d100	100	Percentile rolls

Rolling Multiple Dice

For NdX notation (N dice with X sides):

# Roll 3d6 (three six-sided dice)
for i in {1..3}; do echo $((RANDOM % 6 + 1)); done | paste -sd+ | bc

import random

def roll(n, sides, modifier=0):
    rolls = [random.randint(1, sides) for _ in range(n)]
    total = sum(rolls) + modifier
    return {"rolls": rolls, "modifier": modifier, "total": total}

# Examples
print(roll(3, 6))        # 3d6
print(roll(1, 20, 5))    # 1d20+5
print(roll(2, 8, -1))    # 2d8-1

Parsing Dice Notation

When the user provides dice notation like "2d6+3", parse it:

import re
import random

def parse_and_roll(notation: str) -> dict:
    match = re.match(r"(\d+)?d(\d+)([+-]\d+)?", notation.strip().lower())
    if not match:
        return {"error": f"Invalid notation: {notation}. Use format: NdX+M (e.g., 2d6+3)"}
    
    n = int(match.group(1) or 1)
    sides = int(match.group(2))
    modifier = int(match.group(3) or 0)
    
    rolls = [random.randint(1, sides) for _ in range(n)]
    total = sum(rolls) + modifier
    
    result = f"{notation} → {rolls}"
    if modifier:
        result += f" {'+' if modifier > 0 else ''}{modifier}"
    result += f" = {total}"
    
    return {"notation": notation, "rolls": rolls, "modifier": modifier, "total": total, "display": result}

# Usage
print(parse_and_roll("2d6+3"))
print(parse_and_roll("d20"))
print(parse_and_roll("4d8-2"))

Gotchas

• Bash $RANDOM range: $RANDOM produces 0-32767. For dice this is fine, but for very large ranges use Python's random.randint().
• Inclusive ranges: Dice rolls are always 1 to N inclusive. random.randint(1, N) is correct; random.randrange(1, N) excludes N.
• Modifier can be negative: "d20-2" means subtract 2 from the roll. The total can go below 1.
• Always show individual rolls: When rolling multiple dice, show each die result plus the total — users want to see the breakdown.

Validation

After rolling:

1. Each individual die result is within 1 to sides (inclusive)
2. Total equals sum of individual rolls plus modifier
3. Display shows the full breakdown (individual rolls + modifier = total)