Thanks for the reply, but those things don't really help: they aren't run-time mechanisms. Imagine gcc didn't have the "-MD" option: how would you know what header files are used (without preprocessing the C files)? strace tells you precisely which files gcc reads. Other programs don't have a -MD equivalent, hence the desire to trace system-calls at run time. Anyone who's used Clearcase (clearmake) should understand how nice it is to write makefiles without dependencies. Dave.