When fsv is invoked with the --help option, it prints out a usage summary:
| bash$ fsv --help
fsv - 3D File System Visualizer
      Version 0.9
Copyright (C)1999 Daniel Richard G. <skunk@mit.edu>
Usage: fsv [rootdir] [options]
  rootdir      Root directory for visualization
               - (defaults to current directory)
  --mapv       Start in MapV mode (default)
  --treev      Start in TreeV mode
  --help       Print this help and exit
 | 
Options and arguments
Specifies the base of the directory tree for fsv to work in. Everything inside this directory will be scanned, and subsequently translated into geometry.
If no value is given, fsv works in the directory it is invoked from.
Starts the program in MapV visualization mode. (This is the default)
Starts the program in TreeV visualization mode.
Prints out the usage summary and exits.