IO.popen(command, :err=>[:child, :out]) {|ls_io|
  ls_io.each do |line|
   print line
 end
 }

1%r2%r3%r…100%
task finished

IO.popen(commande, :err=>[:child, :out]) {|ls_io|
while true
  byte=ls_io.read(1)
  if byte.nil?
    break
  end
   print byte
end
}