Chef - Passing output of one resource as input to the next

There are a couple of ways to do that.

One is via lazy

directory '/tmp' 

file '/tmp/alex.txt' do
  content 'sudo make me a sandwitch'
end 

ruby_block "something" do
    block do
      command = 'cat /tmp/alex.txt'
      command_out = shell_out(command)
      node.set['a'] = command_out.stdout
    end
    action :create
end 

file '/tmp/alex2.txt' do
  action :create
  owner 'root'
  group 'root'
  mode '0644'
  content lazy { node['a'] }
end