这是我的代码：

local getDLFile = function(fileToDL)
            local path = system.pathForFile(fileToDL,system.DocumentsDirectory )
            local myFile = io.open( path,"w+b" ) 
            http.request{ 
                url = "http://www.testfile.com/"..fileToDL,sink = ltn12.sink.file(myFile),}
 
            -- i don't know what is the Syntax
            if myFile.size == 743 bytes then
                 myFile.delete
            end             
 
end

任何人都可以帮助我关于我的情况吗？