logWatch.sh

#!/bin/ash                                                                                                                                   
# This script filters the logs and send it via mail                                                                                          

# Installation on openwrt                                                                                                                    
#- opkg update && opkg install diffutils                                                                                                     
#- install and setup ssmtp (https://fleshandmachines.wordpress.com/2014/09/14/openwrt-automatic-email-sending/)                              
#- add it to crontab                                                                                                                         

# Rules                                                                                                                                      
RULES="grep -v info"                                                                                                                         
MAIL="[email protected]"                                                                                                             

# DO NOT TOUCH                                                                                                                               
OLD_LOG=/tmp/oldlog                                                                                                                          
NEW_LOG=/tmp/newlog                                                                                                                          

touch $OLD_LOG                                                                                                                               
logread > $NEW_LOG                                                                                                                           

DIFF=$(diff $NEW_LOG $OLD_LOG | grep -v ^--- | grep ^- | $RULES)                                                                                                      

if [ -z "$DIFF" ]; then                                                                                                                      
    echo "No changes exit"                                                                                                                   
    exit 0                                                                                                                                   
fi                                                                                                                                           
echo "Mailing logs"                                                                                                                          
echo -e "Subject: Log activity detected on $HOSTNAME\n\n$DIFF" | ssmtp $MAIL                                                                 
mv $NEW_LOG $OLD_LOG