Basic integration with pure Lua with system shell. This allows executing system commands as Lua functions. The command output is returned as a Lua string

Lua shell integration.lua

-- Create a table to hook __index metamethod of _ENV
_ENV_mt = {}

function _ENV_mt:__index(key)
  -- If requested index exists, return them
  if rawget(_ENV,key) then
    return rawget(_ENV,key)
  end
  
  -- If environment variable exists return them
  if os.getenv(key) then
    return os.getenv(key)
  end

  -- Check if executable exists in PATH variable
  local separator = package.config:sub(1,1) == "/" and ":" or ";"
      local found = false
  for path in os.getenv("PATH"):gmatch("[^"..separator.."]+") do
    local file_path = path..(separator == ":" and "/" or "\\")..key

    local executable=io.open(file_path,"r")
    if executable~=nil then 
        io.close(executable)
        found = true
        break
    end
  end

  -- If not return nil
  if found == false then
    return nil
  end

  -- Let's create a memoize function (a function with properties)
     local memoize = {} -- The memoize table 
  local memoize_mt = {__index = memoize} -- The memoize metatable

  memoize.cmd=key -- Let's "memoize" requested cmd on key "cmd" 

  -- This allow to call a table as function
  function memoize_mt:__call(args)
    -- Since args may contains spaces we need to hold cmd and args with single quotes
    local cmd_line = "'"..self.cmd.."'"
    for _,arg in ipairs(args) do 
      cmd_line = cmd_line.." '"..arg.."'"
    end

    -- Do a simple popen read command output
    local file = assert(io.popen(cmd_line, 'r'))
    local output = file:read('*all')
    file:close()

    -- So return them
    return output
  end

  -- At last step we return our memoize function
  return setmetatable(memoize,memoize_mt)
end

setmetatable(_ENV, _ENV_mt) --And hook _ENV with created metatable

-- ls {"-la" ; "/"}