Random and rounding in many programming languages

In short: Almost every language has a function for random numbers and one for rounding down. Names and behaviour differ in detail.

In more detail: The table shows how to write a random number from 1 to 6 and rounding down in common languages. Security-relevant random values always need the cryptographic generator of the respective language.

In detail

Language	Die 1–6	Round down
JavaScript	Math.floor(Math.random()*6)+1	Math.floor(x)
Java	new Random().nextInt(6)+1 or ThreadLocalRandom.current().nextInt(1,7)	Math.floor(x)
Python	random.randint(1,6)	math.floor(x)
C	rand() % 6 + 1 (call srand(time(0)) first)	floor(x) from math.h
C++	std::uniform_int_distribution<int>(1,6) with mt19937	std::floor(x)
C#	Random.Shared.Next(1,7)	Math.Floor(x)
Go	rand.IntN(6)+1 (math/rand/v2)	math.Floor(x)
Rust	rng.gen_range(1..=6) (rand crate)	x.floor()
PHP	random_int(1,6)	floor($x)
Ruby	rand(1..6)	x.floor
Kotlin	(1..6).random()	floor(x)
Swift	Int.random(in: 1...6)	x.rounded(.down)
SQL	FLOOR(RAND()*6)+1 (MySQL)	FLOOR(x)
Bash	$((RANDOM % 6 + 1))	integer division

• Secure: Python secrets, Java SecureRandom, JS crypto.getRandomValues, C# RandomNumberGenerator, PHP random_int, Go crypto/rand.
• Modulo trap: rand() % n is slightly biased when the number range is not divisible by n.
• Seed: the same start value (seed) gives the same sequence, useful for tests.

See also: Math.random and Math.floor, Random numbers: pseudo-random and true random