ANONYMOUS wrote: No answer for the 2nd question. I started to write a small clarification for it, but then realised that there is no correct answer. For example, in determining which of two files we should copy (from) - we presume that 2 candidate files have the same relative location, same filenames, (now) same modification-time, (hmmm, OK, same size, ....., but different contents. There's no way to meaningfully state which should be the file to be copied. And even if we someone considered the contents/text, which file should win? So, when testing your projects, we'll ensure that no 2 files have the same modification time (avoiding the potential problem). Your approach may be wrong. You first identify what should be copied and then (if no -n option) you do the copying. Providing the -n option also sets the -v option and so, whether actually copy files or not, you may wish to annotate what your program is doing (or *would be doing* is -n is provided).