#!/bin/bash

LOWBYTES="1000000000" # 1000000000 = 1 GB
HIGHPERCENT="10"

df -B1 -x devtmpfs -x tmpfs | grep -v Filesystem | while read p
do
  device=$(echo $p | awk '{print $1}')
  bytes=$(echo $p | awk '{print $4}')
  percent=$(echo $p | awk '{print $5}' | sed 's/%//')
  if [ "$bytes" -lt "$LOWBYTES" ]
  then
    df -H -x devtmpfs -x tmpfs
    exit
  elif [ "$percent" -gt "$HIGHPERCENT" ]
  then
    df -H -x devtmpfs -x tmpfs
    exit
  fi
done