[NTG-context] passing buffer to lua functions

Dear all, I'm trying to implement a very simple filter mechanism in lua like this: \def\test#1{% \startlua local pipe, str pipe = io.popen("./my_filter '\luaescapestring{#1}'", "r") str = pipe:read("*a") tex.print(str) pipe:close() \stoplua } \test{% line 1 line 2 } The issue I have is that the argument of test has its line breaks removed in the process (i.e. the filter my_filter sees a single line argument). How to prevent this while keeping the lua escape at the same time? (I know I can implement such a thing with executecommand and using buffers written to files, but I would like to avoid writing on the hard disk.) Olivier