[NTG-context] escaping quotes in \ctxlua

Dear list, I have the following sample: \starttext \startluacode tex.print(os.getenv("USER") \stopluacode \ctxlua{tex.print(os.getenv("USER")} \stoptext How can I escape the quotes in the \ctxlua command? Many thanks for your help, Pablo -- http://www.ousia.tk