Synchronize time between hardware clock and NTP server

ntp2hwc.sh

#!/bin/bash
#
# Author: Thomas (https://raspberrypi.stackexchange.com/users/9732/thomas)
# Modified-by: Julius Bullinger (https://github.com/sqrt)
# Version: 0.2
#
# Synchronize time between hardware clock and NTP server

# Make sure only root can run this script
if [[ $EUID -ne 0 ]]; then
    echo "This script must be run as root." 1>&2
    exit 1
fi

# Location of logfile
LOGFILE="/var/log/ntp2hwc.log"
if [ ! -f $LOGFILE ]; then
    touch $LOGFILE
fi

# Set the maximum allowed difference in seconds between Hardware and System Clock
max_diff="1"

msg_connection="Connected to NTP server."
msg_noconnection="No connection to NTP server."

# Check for NTP connection
if ( ntpq -p | grep -q "^\*"  ); then
    echo "$msg_connection"
    echo "---------------------------------"

    hwclock_secs=$(sudo hwclock --debug | grep "^Hw clock time" | awk '{print $(NF-3)}')
    echo "Hardware Clock : $hwclock_secs sec"

    sysclock_secs=$(date +"%s")
    echo "System Clock    : $sysclock_secs sec"
    echo "---------------------------------"

    # Absolute difference between the two clocks
    clock_diff=$((hwclock_secs-sysclock_secs))
    clock_diff=${clock_diff#-}

    echo "Difference: $clock_diff sec"

    msg_diff="Hardware Clock difference: $clock_diff sec"
    if [ "$clock_diff" -gt "$max_diff" ] ; then
        echo "---------------------------------"
        echo "The difference between Hardware and System Clock is more than $max_diff sec."
        echo "Hardware Clock will be updated"

            # Update hwclock from system clock
            sudo hwclock -w
            msg_diff="$msg_diff --> HW-Clock updated."
        fi
        if ! (awk '/./{line=$0} END{print line}' $LOGFILE | grep -q "$msg_connection") || [ "$clock_diff" -gt "$max_diff" ]; then
            echo "$(date): $msg_connection. $msg_diff" >> $LOGFILE
        fi
    else

    # No NTP connection
    echo "$msg_noconnection"
    if ! (awk '/./{line=$0} END{print line}' $LOGFILE | grep -q "$msg_noconnection"); then
        echo "$(date): $msg_noconnection" >> $LOGFILE
    fi
fi