Bash script for cron to check if motion is running and free disk space

check_motion.sh

#!/bin/bash

SERVICE='motion'
RUN_COMMAND='nice -n 10 /usr/local/bin/motion &'
LOGFILE=/home/pi/motion/motion.log
VOPATH=/media/data/motion  # video output directory
LIMIT=90  # maximum disk usage

if [ ! $(pidof $SERVICE) ]
then
  # process not running, starting
  echo "[!!!] [$(date +%c)] check_motion.sh - $SERVICE is not running, starting '$RUN_COMMAND'" >> $LOGFILE
  $($RUN_COMMAND)
fi

if [ $(df -P $VOPATH | awk '{ gsub("%",""); capacity = $5 }; END { print capacity }') -gt $LIMIT ]; then
  echo "Free space is less than $LIMIT, removing 10 oldest files."
  cd $VOPATH
  rm $(ls -tr | awk 'NR<10')
fi