module Closure::Popen

def self.popen(*cmd)
  # pipe[0] for read, pipe[1] for write
  pw, pr, pe = IO.pipe, IO.pipe, IO.pipe
  pid = fork {
    pw[1].close
    STDIN.reopen(pw[0])
    pw[0].close
    pr[0].close
    STDOUT.reopen(pr[1])
    pr[1].close
    pe[0].close
    STDERR.reopen(pe[1])
    pe[1].close
    exec(*cmd)
  }
  pw[0].close
  pr[1].close
  pe[1].close
  pi = [pw[1], pr[0], pe[0]]
  pw[1].sync = true
  begin
    if block_given?
      yield(*pi)
    end
  ensure
    pi.each{|p| p.close unless p.closed?}
  end
  pid
end