ruby function to check if passwordless is setup

sshable.rb

def sshable?(nodes_arr, ssh_user, ssh_key, port=22)
  nodes_arr.each do |instance|
    `ssh -t -t -o ConnectTimeout=2 -o StrictHostKeyChecking=no -o BatchMode=yes -i #{ssh_key} #{ssh_user}@#{instance} "echo" &>/dev/null`
    #ssh options used:
      #ConnectTimeout => timeout the ssh session
      #StrictHostKeyChecking => dont check for host key
      #BatchMode => dont ask for password, of prompted for password exit out
      #-t -t => Force pseudo-tty allocation, Multiple -t options force tty allocation, even if ssh has no local tty
    unless $?.success?
      puts "[Error]: cannot ssh into instance: #{instance}"
      exit 1
    end
  end
end

#Usage:
nodes = %w(localhost 127.0.0.1)
sshable(nodes, 'root', '~/.ssh/id_rsa')