[CentOS] Detect file change

Hello everyone!

How can I detect if a folder have changed (sync logic) than run a script 
if it's true?
I found this script over the net, but I think it's such complicated for 
that simple thing...

    #!/bin/bash

    ############### detectdir.sh by Jagbir Singh #################
    #
    # script to detect changes in directory.
    #
    ###############################################################

    # directory to watch
    DIR="/var/www/vhosts"

    # store current statistics of dir
    OLD=`stat -t $DIR`

    while true
    do

    # take a new snapshot of stats
    NEW=`stat -t $DIR`

    # compare it with old
    if [ "$NEW" != "$OLD" ]; then

    echo "changed!" ## you may want to comment this

    # take current listing of dir in a file. domains may be added or
    removed.
    ls $DIR --file-type | grep "\/" | sed 's/\///' > /tmp/dir.list

    # open file and you can now process entries in it
    exec 10
    let count=0

    while read LINE <&10; do

    # currently printed on screen, can supply this as arg to rSync,
    discussed later
    echo $LINE/httpdocs/
    echo
    ((count++))
    done

    # take snapshot again and store it in both old and new vars
    NEW=`stat -t $DIR`
    OLD=$NEW
    exec 10>&-
    fi

    # i'm using 3 secs calm time, you should update this as per your
    environment
    sleep 3
    done


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