#!/bin/bash

cron=/etc/crontab
md5old=/etc/crontab_save

log=/var/log/check_crontab.log

printf "##### %s #####\n" "$(date)" >>$log
if [ ! -f $md5old ]
then
    printf "Error: %s don't exist\nCreating %s ...\n" "$md5old" "$md5old" >>$log
    md5sum $cron >$md5old
    exit 0
fi
if [ ! -s $md5old ]
then
    printf "Error: %s is empty\nadding md5 hash to %s ...\n" "$md5old" "$md5old" >>$log
    md5sum $cron >$md5old
    exit 0
fi
if [ ! $(md5sum -c $md5old 2>/dev/null | grep $cron | cut -d' ' -f2) = "OK" ]
then
    printf "Error: %s modified\nsending mail ...\n" >>$log
    echo "crontab has changed T_T" | mail -s "!!! PANIC !!! PANIC !!!! PANIC !!!" root
else
    printf "file OK\n" >>$log
fi