arg parsing

#set some defaults
BUFLEN=80
DOSUDO=0
FFMPEG=0
VOLUME=100
MPLAYER=0
showhelp()
{
  echo 'Supported flags:'
  echo '-b, --buffer-time  : Specify duration of buffer. Default: '"$BUFLEN"'.'
  echo '-f, --use-ffmpeg   : Use ffmpeg instead of an arecord -> aplay pipe.'
  echo '-c, --cap-device   : Use specified device for capturing'
  echo '-m, --use-mplayer  : Use ffmpeg to capture and pipe to mplayer.'
  echo '-r, --root, --nice : Run as root so process can be given higher priority.'
  echo '-v, --volume       : Set volume percentage (implies -f).'
  echo '-h, --help         : Show this help message.'
}
while [ "$#" -gt 0 ]; do
  case "$1" in
    '-b' | '--buffer-time' | '--buffer')
      # shift required whenever an arg-value pair needs passed
      shift 1
      if [ "$#" -gt 0 ]; then
        BUFLEN="$1"
      else
        1>&2 echo 'Error: need a value for buffer duration if -b is passed.'
        exit 1
      fi
      ;;
    '-f' | '--use-ffmpeg')
      FFMPEG=1
      ;;
    '-m' | '--use-mplayer')
      FFMPEG=1
      MPLAYER=1
      ;;
    '-r' | '--root' | '--nice')
      DOSUDO=1
      ;;
    '-v' | '--volume')
      if [ "$#" -gt 1 ]; then
        FFMPEG=1 # -v implies ffmpeg
        VOLUME="$2"
        VOLUME="$(echo '10 k '"$VOLUME"' 100 /p' | dc)"
        shift # param needs a shift-out
      else
        echo 'Error: No volume level to set was given but -v was passed.'
        exit 1
      fi
      ;;
    '-c' | '--cap-device')
      if [ "$#" -gt 1 ]; then
        CAPTURE_DEV="$2"
        shift # param needs a shift-out
      else
        echo 'Error: No volume level to set was given but -v was passed.'
        exit 1
      fi
      ;;
    '-h' | '--help')
      showhelp
      exit 0
      ;;
    *)
      1>&2 echo 'Error: unknown parameters passed to program.'
      1>&2 showhelp
      ;;
  esac
  shift 1
  if [ "$1" = '-b' ]; then
    if [ -z "$2" ]; then
      BUFLEN="$2"
    fi
  fi
done