inotifywait

#!/bin/sh

FILE_TO_WATCH="/tmp/ndnproxymain.conf"
HASH_FILE="/var/run/ipset_watcher.hash"

# Commands to execute when the file changes
COMMANDS_ON_CHANGE="
    ipset flush bypass
"

# Function to calculate MD5 hash of the file
calculate_md5() {
    md5sum "$FILE_TO_WATCH" | awk '{ print $1 }'
}

# Function to execute commands when the file changes
on_file_change() {
    eval "$COMMANDS_ON_CHANGE"
}

# Function to start the script
start() {
    # Load previous hash from file if it exists
    if [ -f "$HASH_FILE" ]; then
        PREVIOUS_HASH=$(cat "$HASH_FILE")
    else
        PREVIOUS_HASH=$(calculate_md5)
        echo "$PREVIOUS_HASH" > "$HASH_FILE"
    fi

    # Monitor the file for changes
    inotifywait -q -m -e modify,attrib,close_write "$FILE_TO_WATCH" | while read; do
        CURRENT_HASH=$(calculate_md5)
        if [ "$CURRENT_HASH" != "$PREVIOUS_HASH" ]; then
            PREVIOUS_HASH="$CURRENT_HASH"
            echo "$PREVIOUS_HASH" > "$HASH_FILE"
            on_file_change
        fi
    done &
    echo $! > /var/run/ipset_watcher.pid
}

# Function to stop the script

stop() {
    if [ -f /var/run/ipset_watcher.pid ]; then
        PID=$(cat /var/run/ipset_watcher.pid)
        kill "$PID"
        sleep 1
        if ps -p "$PID" > /dev/null; then
            echo "Process $PID still running, sending SIGKILL"
            kill -9 "$PID"
        fi
        rm /var/run/ipset_watcher.pid
    else
    # Use killall as a fallback
    killall inotifywait
    fi
}

# Function to check the status of the script
status() {
    if [ -f /var/run/ipset_watcher.pid ]; then
        PID=$(cat /var/run/ipset_watcher.pid)

        # Check if the PID is in the ps output
        if ps | grep -w "$PID" | grep -v grep > /dev/null; then
            echo "Monitoring process is running (PID: $PID)."
        else
            echo "Monitoring process not running, but PID file exists."
        fi
    else
        echo "Monitoring process is not running."
    fi
}

case "$1" in
    start)
        start
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    status)
        status
        ;;
    *)
        echo "Usage: $0 {start|stop|restart|status}"
        exit 1
        ;;
esac

exit 0