module Process

def get_exitcode(pid)


when stdin, stdout or stderr are set to custom values.
the process isn't recognized as a child process (ECHILD). This happens for example
is still running. The usual way of calling Process.wait doesn't work when
This method is very handy for finding out if a process started with Process.create

is still running. Note that the process doesn't have to be a child process.
Returns the exitcode of the process with given +pid+ or nil if the process 
def get_exitcode(pid)
  handle = OpenProcess(PROCESS_QUERY_INFORMATION, 0, pid)
  if handle == INVALID_HANDLE_VALUE
    raise SystemCallError.new("OpenProcess", FFI.errno)
  end
  begin
    buf = FFI::MemoryPointer.new(:ulong, 1)
    unless GetExitCodeProcess(handle, buf)
      raise SystemCallError.new("GetExitCodeProcess", FFI.errno)
    end
  ensure
    CloseHandle(handle)
  end
  exitcode = buf.read_int
  if exitcode == STILL_ACTIVE
    nil
  else
    exitcode
  end
end