mkdir /root/bin
touch /root/bin/periodic_mca_log_monitoring.bash
chown root:wheel /root/bin/periodic_mca_log_monitoring.bash
chmod 700 /root/bin/periodic_mca_log_monitoring.bash
vi /root/bin/periodic_mca_log_monitoring.bash

#!/bin/bash
declare MCA_MESSAGES
declare MCA_LOG_PATH="/var/log/MCA-messages"
declare EMAIL_ADDRESS="email@domain.com"

# Load all MCA related messages from the previous 10-minute-timeframe from /var/log/messages.0.bz2 (this is previous / rotated messages logfile)
#   If the errors occured around the time the messages logfile was rotated, then it is important to check the previous file too.
[[ -f /var/log/messages.0.bz2 ]] && MCA_MESSAGES="$(bzcat /var/log/messages.0.bz2 | egrep "$(date -v -10M "+%b %e %H:%M" | sed 's/.$//').*$(hostname -s) MCA.*")"

# If something is in ${MCA_MESSAGES}, then append a new-line
[[ ! -z "${MCA_MESSAGES}" ]] && MCA_MESSAGES+=$'\n'

# Append all MCA related messages from the previous 10-minute-timeframe from /var/log/messages
[[ -f /var/log/messages ]] && MCA_MESSAGES+="$(cat /var/log/messages | egrep "$(date -v -10M "+%b %e %H:%M" | sed 's/.$//').*$(hostname -s) MCA.*")"

# If something is in ${MCA_MESSAGES}, then store it in ${MCA_LOG_PATH} and send an email. If the email command fails, then 'exit 1'
if [[ ! -z "${MCA_MESSAGES}" ]]; then
  echo "${MCA_MESSAGES}" >>"${MCA_LOG_PATH}"
  mail -s "TrueNAS $(hostname): Alerts" ${EMAIL_ADDRESS} <<< "MCA Errors were found in /var/log/messages:"$'\n\n'"${MCA_MESSAGES}" || exit 1
fi

# If the script completes successfully then 'exit 0'
exit 0

mkdir /root/bin
touch /root/bin/init_mca_log_monitoring.bash
chown root:wheel /root/bin/init_mca_log_monitoring.bash
chmod 700 /root/bin/init_mca_log_monitoring.bash
vi /root/bin/init_mca_log_monitoring.bash

#!/bin/bash
declare MCA_MESSAGES_ALL MCA_MESSAGES_NEW
declare MCA_MESSAGE
declare MCA_LOG_ENTRIES="$(cat "${MCA_LOG_PATH}")"
declare MCA_LOG_ENTRY
declare MCA_LOG_PATH="/var/log/MCA-messages"
declare EMAIL_ADDRESS="email@domain.com"
declare OLDIFS

# Load all MCA related messages from /var/log/messages.0.bz2 (this is previous / rotated messages logfile)
#   If the errors occured around the time the messages logfile was rotated, then it is important to check the previous file too.
[[ -f /var/log/messages.0.bz2 ]] && MCA_MESSAGES_ALL="$(bzcat /var/log/messages.0.bz2 | egrep ".*$(hostname -s) MCA.*")"

# If something is in ${MCA_MESSAGES_ALL}, then append a new-line
[[ ! -z "${MCA_MESSAGES_ALL}" ]] && MCA_MESSAGES_ALL+=$'\n'

# Append all MCA related messages from /var/log/messages
[[ -f /var/log/messages ]] && MCA_MESSAGES_ALL+="$(cat /var/log/messages | egrep ".*$(hostname -s) MCA.*")"

# Only store MCA messages that are not found in the MCA-log-file, in the ${MCA_MESSAGES_NEW} variable
OLDIFS="$IFS"                                                    # Backup $IFS
IFS=$'\n'                                                        # To loop line-per-line
for MCA_MESSAGE in ${MCA_MESSAGES_ALL}; do
  for MCA_LOG_ENTRY in ${MCA_LOG_ENTRIES}; do
    [[ "${MCA_MESSAGE}" == "${MCA_LOG_ENTRY}" ]] && continue 2   # Jump out of the ${MCA_MESSAGES_ALL}-loop, if ${MCA_MESSAGE} was already in ${MCA_LOG_ENTRIES}
  done
  MCA_MESSAGES_NEW+="${MCA_MESSAGE}"$'\n'                        # If ${MCA_MESSAGE} was not found in ${MCA_LOG_ENTRIES}, then add it to ${MCA_MESSAGES_NEW}
done
MCA_MESSAGES_NEW="${MCA_MESSAGES_NEW%$'\n'}"                     # Remove trailing new-line
IFS="$OLDIFS"                                                    # Restore $IFS from backup

# If something is in ${MCA_MESSAGES_ALL}, then store it in ${MCA_LOG_PATH} and send an email. If the email command fails, then 'exit 1'
if [[ ! -z "${MCA_MESSAGES_NEW}" ]]; then
  echo "${MCA_MESSAGES_NEW}" >>"${MCA_LOG_PATH}"
  mail -s "TrueNAS $(hostname): Alerts" ${EMAIL_ADDRESS} <<< "MCA Errors were found in /var/log/messages:"$'\n\n'"${MCA_MESSAGES_NEW}" || exit 1
fi

# If the script completes successfully then 'exit 0'
exit 0