curl = require("luacurl")
--下載這個頁面的.java檔案
downloadurl = "http://www.cs.princeton.edu/~rs/talks/LLRB/Java/"
function get_html(url, c)
    local result = { }
    if c == nil then
        c = curl.new()
    end
    c:setopt(curl.OPT_URL, url)
    c:setopt(curl.OPT_WRITEDATA, result)
    c:setopt(curl.OPT_WRITEFUNCTION, function(tab, buffer)     --call back函式，必須有
        table.insert(tab, buffer)                      --tab引數即為result，參考http://luacurl.luaforge.net/
        return #buffer
    end)
    local ok = c:perform()
    return ok, table.concat(result)             --此table非上一個table，作用域不同
end

ok, html = get_html(downloadurl)
if ok then
--分析頁面返回的.java的地址
		for k in string.gfind(html, ">(%w+.java)<") do
      ok,javacode = get_html(downloadurl .. k)
      file = io.open("./"..k, "w");
   		if(file) then
   			file:write(javacode);
   			file:close();
   		end
 		end
else
    print ("Error" )
end