Psych::Stream is a streaming YAML emitter. It will not buffer your YAML, but send it straight to an IO.

Here is an example use:

stream = Psych::Stream.new($stdout)
stream.start
stream.push({:foo => 'bar'})
stream.finish

YAML will be immediately emitted to $stdout with no buffering.

Psych::Streaming#start will take a block and ensure that Psych::Visitors::YAMLTree#finish is called, so you can do this form:

stream = Psych::Stream.new($stdout)
stream.start do |em|
  em.push(:foo => 'bar')
end