An example using uv.spawn with lua_promise

spawn_ls_promise.lua

-- An example using uv.spawn with Promise.
-- (c) 2014 Hiroaki Nakamura
-- MIT license
-- 
-- Used libraries
-- * luv: https://github.com/luvit/luv
-- * lua_promise: https://github.com/friesencr/lua_promise

local uv = require("luv")
require("Promise")

function runCommand(command, args)
  local p = Promise:new()

  local options = {
    stdio = {
      nil,
      1,
      2
    }
  }

  local child, pid = uv.spawn(command, args, options)
  function child:onexit(code, signal)
    uv.close(child)
    p:resolve(code, signal)
  end

  p.child = child
  p.pid = pid
  return p
end

function after(ms)
  local p = Promise:new()
  local timer = uv.new_timer()
  function timer:ontimeout()
    uv.timer_stop(timer)
    uv.close(timer)
    p:resolve()
  end
  uv.timer_start(timer, ms, 0)
  return p
end

local p = runCommand("sleep", {"3"})
p:done(function(code, signal)
  print("sleep", "code", code, "signal", signal)
end)
:done(function()
  runCommand("ls", {"-l"})
  :done(function(code, signal)
    print("ls", "code", code, "signal", signal)
  end)
  :done(function()
    runCommand("pwd")
    :done(function(code, signal)
      print("pwd", "code", code, "signal", signal)
    end)
  end)
end)

after(1000)
:done(function()
  uv.process_kill(p.child)
end)

repeat
until uv.run('once') == 0