This is quite possibly just a silly question, and I suspect I already know the answer, but I might learn something new, so ...
I recently learned about the CDPATH environment variable, which lists a number of directories for cd to search through - in a sense joining those directories to the current directory, and I wondered if there is something similar for ls and other commands - so that ls would list not only the current directory, but the ones that are 'joined' to it, and the files will be available as files in the current directory. One reason why it might be desirable is if you have a directory with a number of files that you want to be visible in the home directories of several users.
I'm not saying this would be hugely useful or beneficial, and I know a number of ways in which to achieve a similar effect, eg with symbolic links; it was just a thought experiment.
