timeout_popen.lua

local function timeout_popen(timeout, ...)
  local outerpiper, outerpipew = nixio.pipe()
  if nixio.fork() == 0 then
    outerpiper:close()
    local innerpiper, innerpipew = nixio.pipe()
    local pid = nixio.fork()
    if pid == 0 then
      outerpipew:close()
      innerpiper:close()
      nixio.dup(innerpipew, nixio.stdout)
      innerpipew:close()
      local ret, errno, errstr = nixio.exec(...)
      local cmd = ...
      io.stderr:write("exec(\"" .. table.concat({...}, "\", \"") .. "\"): " .. errstr .. " (" .. errno .. ")\n")
      os.exit(1)
    end
    innerpipew:close()
    local endtime = os.time() + timeout
    while true do
      local fdnum, fds = nixio.poll({{fd = innerpiper, events = nixio.poll_flags("in")}}, os.difftime(endtime, os.time())*1000)
      if fdnum == false then
        if os.difftime(endtime, os.time()) <= 0 then
          nixio.kill(pid, 15)
          break
        end
      else
        if nixio.poll_flags(fds[1].revents)["in"] then
          nixio.splice(innerpiper, outerpipew, 4096, nixio.splice_flags("nonblock"))
        else
          if nixio.waitpid(pid, "nohang") == pid then
            -- child exited
            break
          end
        end
      end
    end
    innerpiper:close()
    outerpipew:close()
    os.exit()
  end
  outerpipew:close()
  return outerpiper
end