This function scan the folder(s) provided, and search for all files or only for those matching a wild card, specified through the * syntax.
The search can be don recursively or not and a different recursion rule can be set for each folder provided.
Depending upon an optional input argument, the function can simply return the file names or their full path.
To get the full path of a given file, FUF doesn't use the "which" command, therefore it normally works also with java function that are not loaded.
After completion, the working directory is set to the current directory at the time of the function call.