proc.vim

python import vim, os

function! Spawn(argv)
  python << EOM
argv = vim.eval('a:argv')
pid = os.spawnvp(os.P_NOWAIT, argv[0], argv)
vim.command('let pid = %d' % pid)
EOM
  return pid
endfunction

function! Wait(pid)
  python <<EOM
pid = int(vim.eval('a:pid'))
_, st = os.waitpid(pid, 0)
vim.command('let ret = %d' % os.WEXITSTATUS(st))
EOM
  return ret
endfunction

function! Test()
  let pid = Spawn(['/bin/sh', '-c', 'exit 42'])
  echomsg 'pid =' pid
  call system('sleep 3')
  let st = Wait(pid)
  echomsg 'ret =' st
endfunction