[ruby] How to generate a random number between a and b in Ruby?

To generate a random number between 3 and 10, for example, I use: rand(8) + 3

Is there a nicer way to do this (something like rand(3, 10)) ?

def random_int(min, max)
    rand(max - min) + min
end

And here is a quick benchmark for both #sample and #rand:

irb(main):014:0* Benchmark.bm do |x|
irb(main):015:1*   x.report('sample') { 1_000_000.times { (1..100).to_a.sample } }
irb(main):016:1>   x.report('rand') { 1_000_000.times { rand(1..100) } }
irb(main):017:1> end
       user     system      total        real
sample  3.870000   0.020000   3.890000 (  3.888147)
rand  0.150000   0.000000   0.150000 (  0.153557)

So, doing rand(a..b) is the right thing

Just note the difference between the range operators:

3..10  # includes 10
3...10 # doesn't include 10

For 10 and 10**24

rand(10**24-10)+10

See this answer: there is in Ruby 1.9.2, but not in earlier versions. Personally I think rand(8) + 3 is fine, but if you're interested check out the Random class described in the link.

rand(3..10)

Kernel#rand

When max is a Range, rand returns a random number where range.member?(number) == true.

Random.new.rand(a..b) 

Where a is your lowest value and b is your highest value.