Generate random and complex passwords

password.rb

#!/usr/bin/env ruby
# coding: utf-8

length = 12

if ARGV.size > 0 && (ARGV[0].to_i.to_s == ARGV[0]) &&
    ARGV[0].to_i >= 4 && ARGV[0].to_i <= 128
  length = ARGV[0].to_i
end

special = ' !"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~'.split('')
alpha_lower = ('a'..'z').to_a
alpha_upper = ('A'..'Z').to_a
num = ('0'..'9').to_a
all = special + alpha_upper + alpha_lower + num

a = [special, alpha_upper, alpha_lower, num].map {|i| i.sample}
b = (length - a.length).times.collect { all.sample }
password = (a + b).shuffle.join('')

print password