Open3::capture3 for Ruby 1.8.x

capture3.rb

#!/usr/bin/ruby

def capture3(*cmd)
  # Force no shell expansion, by using a non-plain string. See ruby docs:
  #
  # `If the first argument is a two-element array, the first element is the
  # command to be executed, and the second argument is used as the argv[0]
  # value, which may show up in process listings.'
  cmd[0] = [cmd[0], cmd[0]]

  rout, wout = IO.pipe
  rerr, werr = IO.pipe

  pid = fork do
    rerr.close
    rout.close
    STDERR.reopen(werr)
    STDOUT.reopen(wout)
    exec(*cmd)
  end

  wout.close
  werr.close

  out = rout.read
  err = rerr.read
  Process.wait(pid)
  rout.close
  rerr.close
  return [$?, out, err]
end

def test(*cmd)
  st, err, out = capture3(*cmd)
  p st
  p err
  p out
  puts
end

test('ls', '/var')
test('ls', '/foo')
test('lfhlkhladfla')
test('ls && ls')