Скрипт свободного места на диске/NAS

#!/bin/bash
#Скрипт для мониторинга свободного места на NAS
_ssh_key=''
_ssh_user=''
_ssh_host=''
_ssh_disk=''
_ssh_opt='-oKexAlgorithms=diffie-hellman-group14-sha1 -oHostKeyAlgorithms=ssh-rsa'

if [[ -z "$1" ]]; then
  echo "You need to add an argument to run this script"
  exit 1
fi

case "$1" in
  "total")
    _number=1
    ;;
  "used")
    _number=2
    ;;
  "free")
    _number=3
    ;;
  "precent")
    _number=4
    ;;
  "mount")
    _number=5
    ;;
  "full")
    _number=0
    ;;
  *)
    _number=9
    ;;
esac
#echo "${_number}"
if [[ ${_number} -eq 9 ]]; then
  echo "You need to use the correct argument to run this script"
  echo -e "total - total dick space\nused - dick space used\nfree - free dick space\nprecent - precentage of free dick space\nmount - disk mounting locations"
  exit 1
fi

_command="df |grep \"${_ssh_disk}\""
#echo "${_command}"
_df=`ssh -i ${_ssh_key} ${_ssh_opt} ${_ssh_user}@${_ssh_host} "${_command}"`
#echo "${_df}"
_print=`echo ${_df}| awk '{print $'${_number}'}'`

if [[ ${_number} -eq 0 ]]; then
  echo "1K-blocks    Used      Available  Use%   Mounted on"
fi
echo "${_print}"