Hi: I just started using ns simulator. When I run one of the sample files, like "simple.tcl" in ns-2/tcl/ex, it give me this error. Why is that? couldn't open "out.tr": permission denied while executing "open out.tr w" (file "simple.tcl" line 13) child process exited abnormally Thank you very much. -Farnaz Erfan CS Department Purdue University