# Write `input` to process and return its output
	#
	# Writing and reading are processed line by line,
	# reading only when something is available.
	#
	# ~~~
	# var proc = new ProcessDuplex("tr", "[:lower:]", "[:upper:]")
	# assert proc.write_and_read("""
	#     Alice
	#     Bob
	# """) == """
	#     ALICE
	#     BOB
	# """
	# ~~~
	fun write_and_read(input: Text): String
	do
		var read = new Buffer

		# Main loop, read and write line by line
		var prev = 0
		for delimiter in input.search_all('\n') do
			write input.substring(prev, delimiter.after-prev)
			prev = delimiter.after

			while stream_in.poll_in do
				read.append stream_in.read_line
			end
		end

		# Write the last line
		write input.substring_from(prev)
		stream_out.close

		# Read the rest, may be everything for some programs
		read.append stream_in.read_all
		stream_in.close

		# Clean up
		wait
		return read.to_s
	end