Contrary to list.files(), this method guarantees to work
 recursively.  Moreover, when subdirectories are processed recursively,
 directory names are also returned.
## S3 method for class 'default':
listDirectory(pathname, pattern=NULL, recursive=FALSE, allNames=FALSE, fullNames=FALSE,
  ...)character string of the filename pattern passed. See
   list.files() for more details.TRUE, subdirectories are recursively processed,
   otherwise not.TRUE, also files starting with a period are returned.TRUE, the full path names are returned.vector of file names.list.files() is used.