check if files change timestamp in path

mon.sh

#!/usr/bin/env bash

declare -A cached_paths
declare -A processed_paths

cache=$(echo ${TMPDIR:-/tmp})

err () {
  >&2 echo "$1"
  exit 1
}

read_cache () {
  test -f $cache || {
    test -d $cache && {
      cache="$cache/.mon.cache"
      touch $cache
    } || {
      err "cache does not exists $cache"
    }
  }

  while read -r timestamp path; do
    cached_paths[$path]=$timestamp
  done < $cache
}

assert_data () {
  :> $cache
  alert=""

  for path in "${!processed_paths[@]}"; do
    IFS=, read -r timestamp filepath datetime <<< "${processed_paths[$path]}"

    [[ ! -z "${cached_paths[$path]}" && "${cached_paths[$path]}" != "$timestamp" ]] && {
      alert="file $filepath changed at $datetime"
    }

    echo "$timestamp $path" >> $cache
  done

  test -z "$alert" || err "$alert"
}

process_paths () {
  for path in "${!cached_paths[@]}"; do
    processed_paths[$path]="${cached_paths[$path]}"
  done

  for path in $paths; do
    test -d $path || err "path $path does not exists"
    processed_paths[$path]=$(find $path -type f $excludes -exec stat {} --printf="%Y,%n,%y\n" \; 2>/dev/null | sort -n -r | head -1)
  done
}

usage () {
  cat << HELP
  options:
    -c /path/...          cache path
    -p /path/to           path to monitor
    -e /another/path      path to exclude
    -a                    alert mode
    -h                    this help

  examples:
    $0 -a -p /var/www/html/app -p /var/www/html/super_app -e storage/cache
    $0 -a -c /var/cache/mon.cache -p /var/www/html
    $0 -h

  about:
    monitors changes in files timestamp of give path(s) [-p] excluding path(s) [-e] if
    supplied with [-e] option, [-a] alert mode will send alert to ..., if you dont
    supply [-a], it will generate a cache (in [-c] location if supplied) and wont
    alert;
HELP
  exit 0
}



while getopts "c:p:e:ah" o; do
  case "${o}" in
    c)   cache="${OPTARG}" ;;
    p)   paths="$paths ${OPTARG}" ;;
    e)   excludes="$excludes -not -path \"*${OPTARG}*\"" ;;
    *|h) usage ;;
  esac
done
shift $((OPTIND-1))

read_cache
process_paths
assert_data