Here's the code:

#!/bin/bash 
#Filename: disklog.sh 
#Description: Monitor disk usage health for remote systems 


logfile="diskusage.log" 

if [[ -n $1 ]] 
then 
  logfile=$1 
fi 

   # Use the environment variable or modify this to a hardcoded value 
user=$USER 

#provide the list of remote machine IP addresses  
IP_LIST="127.0.0.1 0.0.0.0" 
# Or collect them at runtime with nmap 
# IP_LIST=`nmap -sn 192.168.1.2-255 | grep scan | grep cut -c22-` 

if [ ! -e $logfile ] 
then 
  printf "%-8s %-14s %-9s %-8s %-6s %-6s %-6s %s\n" \
    "Date" "IP address" "Device" "Capacity" "Used" "Free" \
    "Percent" "Status" > $logfile
fi 
 ( 
for ip in $IP_LIST; 
do 
 ssh $user@$ip 'df -H' | grep ^/dev/ > /tmp/$$.df 

 while read line; 
 do 
 cur_date=$(date +%D) 
 printf "%-8s %-14s " $cur_date $ip 
 echo $line | \
     awk '{ printf("%-9s %-8s %-6s %-6s %-8s",$1,$2,$3,$4,$5); }' 

 pusg=$(echo $line | egrep -o "[0-9]+%") 
 pusg=${pusg/\%/}; 
 if [ $pusg -lt 80 ]; 
 then 
 echo SAFE 
 else 
 echo ALERT 
 fi 

 done< /tmp/$$.df 
done 

) >> $logfile

The cron utility will schedule the script to run at regular intervals. For example, to run the script every day at 10 a.m., write the following entry in crontab:

00 10 * * * /home/path/disklog.sh /home/user/diskusg.log 

Run the crontab -e command and add the preceding line.

You can run the script manually as follows:

$ ./disklog.sh

The output for the previous script resembles this:

01/18/17 192.168.1.6    /dev/sda1   106G    53G    49G     52%     SAFE
01/18/17 192.168.1.6    /dev/md1    958G  776G   159G     84%     ALERT