Generate random string in Ruby.

random_string.rb

def random_string(length = 6)
    rand(36**length).to_s(36)
end

random_string2.rb

def random_string
    rand(2**1024).to_s(36).upcase[0..9]
end

random_string3.rb

def random_string(length)
    chars  = ('A'..'Z').to_a + ('a'..'z').to_a + ('0'..'9').to_a
    (1..length).map {
        chars[rand(chars.length)]
    }.join
end