Capture $stdout for a while.

redirect_stdout.rb

require 'stringio'

def capture
  old_stdout, $stdout = $stdout, StringIO.new
  fake_stdout = $stdout
  yield
  $stdout = old_stdout
  fake_stdout.string
end

capture do
  puts 'They sailed away, for a year and a day,'
  puts 'To the land where the Bong-tree grows'
end
#=> "They sailed away, for a year and a day,\nTo the land where the Bong-tree grows\n"

capture do
  `echo "Alas, do more for subshells..."`
end
""