transfer tracks from a Garmin GPS to Google Earth

This is more of a "note to self", because the parameter syntax of gpsbabel is so counter-intuitive:

• gpsbabel -t -i garmin -f /dev/ttyS0 -o kml -F tracks.kml
  (the /dev/ttyS0 refers to the first serial port, to which my Garmin Legend GPS is connected, /dev/ttyS1 would be a second serial port)
• if you get an error:
  Cannot open serial port '/dev/ttyS0': Permission denied
  retry the command as root, or run:
  chmod 666 /dev/ttyS0
  as root
• to transfer waypoints:
  gpsbabel -w -i garmin -f /dev/ttyS0 -o kml -F waypoints.kml