Poor man's IP reachability monitoring and alerting script

ip-monitoring.sh

#/usr/bin/env bash

main() {
  local ip=$1; shift;
  local maxGapMinutes=$1; shift;

  local epochLastSuccess=`date +%s`

  while true; do
    # check if network is good to avoid false alarming
    if [[ `network_is_good` != 'y' ]]; then
      epochLastSuccess=`date +%s`
      echo "*** Network is offline, skipping the test ***"
      continue
    fi

    ping -c 1 "$ip"
    code=$?
    if [[ $code -eq 0 ]]; then
      echo "Ping succeeded."
      epochLastSuccess=`date +%s`
    else
      echo "Failed to ping!"
    fi
    epochCurr=`date +%s`
    gapMinutes=`echo "(${epochCurr} - ${epochLastSuccess})/60" | bc`
    if [[ $gapMinutes -gt $maxGapMinutes ]]; then
      echo "Gap time is $gapMinutes minutes which is larger than $maxGapMinutes minutes. Alerting!"
      make_noise
    fi

    sleep 1
  done
}

network_is_good() {
  ping -c 1 1.1.1.1 &>/dev/null
  if [[ $? -eq 0 ]]; then
    echo "y"
  else
    echo "n"
  fi
}

# a long running function to constantly making sounds
make_noise() {
  while true; do
    echo "Alerting!! Please take action!!"
    afplay /System/Library/Sounds/Glass.aiff
    sleep 1
  done
}

main $@