Simple logfile monitor which counts occurrences of a string and reacts after n hits

monitor-logfile-and-react-on-hits.sh

#!/bin/bash

USE_SYSTEMD_JOURNAL=0
LOGFILE=/var/log/snapper.log
WAIT_FOR_HITS=3
SEARCH_TERM="test 123"

################

if [ ${USE_SYSTEMD_JOURNAL} -lt 1 ] && ! [ -r ${LOGFILE} ]; then
    echo "couldn't read ${LOGFILE}"
    exit 1
fi

COUNTER=0

while [ ${COUNTER} -lt ${WAIT_FOR_HITS} ];
do
    if [ ${USE_SYSTEMD_JOURNAL} -ne 0 ]; then
        ( journalctl -f -n0 & ) | grep -q "${SEARCH_TERM}"
    else
        ( tail -F -n0 ${LOGFILE} & ) | grep -q "${SEARCH_TERM}"
    fi

    let COUNTER=${COUNTER}+1
    echo "HIT ${COUNTER} - $(date +'%Y-%m-%d %H:%M:%S')"
done

################

echo "COUNTER REACHED"
date