test.rb

Signal.trap(:QUIT) do
  puts "QUIT signal sent."
  exit 0
end

puts "Signal.list['QUIT'] => #{Signal.list['QUIT']}"
puts "My pid is #{$$}\n"

loop do
  puts 'I\'m alive!'
  # print "\a" # bell
  sleep 2
end

test.vim

let s:script_path = substitute(substitute(expand('<sfile>'), '\.vim$', '.rb', ''), '\\', '/', 'g')
echo s:script_path

function! TestRun()
  let s:vimproc = vimproc#popen2('ruby ' . s:script_path . ' 12345')
  echo 'launched. (pid:' . s:vimproc.pid . ')'
endfunction

function! TestKill()
  call s:vimproc.kill(3)
  call s:vimproc.waitpid()
  echo 'closed. (pid:' . s:vimproc.pid . ')'
  " debug for vimproc#kill
  " kill seems make zombie process...
  echo 'last errmsg : ' . vimproc#get_last_errmsg()
  echo 'last status : ' . vimproc#get_last_status()
endfunction