https://gist.github.com/1814635

$ ruby genpas.rb

Length of passwords[12]: 13

Number of passwords[3]: 4

Passwords:

ebamazofifira

lufahavelozak

pikisolocamiz

uwosesonymaje

class String
  def randchar
    self[(rand * size).to_i]
  end
end
Vowels = 'aeiouy'
Consonants = 'bcdfghjklmnpqrstvwxz'
VowelsR, ConsonantsR = [Vowels, Consonants].map{|s| /^[#{s}]+$/}
Chars = [Vowels, Consonants]
def gen_pass(len)
  res = ''
  i = (rand * 2).to_i
  while res.size < len
    res << Chars[i].randchar
    i = (i+1) % 2
  end
  res
end

DEFAULT_LENGTH = 12
DEFAULT_NUMBER = 3
require 'optparse'
opts = {}
opt = OptionParser.new
opt.on('-l','--length [LENGTH]',Integer,"length of password (default #{DEFAULT_LENGTH}"){|i| 
  opts[:length] = i || DEFAULT_LENGTH
}
opt.on('-n','--number [COUNT]',Integer, "number of password (default #{DEFAULT_NUMBER}"){|n| 
  opts[:number] = n || DEFAULT_NUMBER
}
opt.on('-h','--help') { puts opt; exit}
opt.parse(ARGV)
unless opts[:length]
  print "Length of passwords[#{DEFAULT_LENGTH}]: "
  s = $stdin.gets
  opts[:length] = s.to_i  if s.to_i > 0
end
unless opts[:number]
  print "Number of passwords[#{DEFAULT_NUMBER}]: "
  s = $stdin.gets
  opts[:number] = s.to_i  if s.to_i > 0
end
opts = {:length=>12, :number=>2}.merge(opts)
puts "Passwords:"
opts[:number].times do
  puts gen_pass(opts[:length])
end