Ping an IP forever and report its reachability

track-icmp-state.sh

#!/usr/bin/env bash
# pings an IP address forever and tracks whether it is accessible
# logs the connection's state change to $STDOUT

ip='8.8.8.8'
track_attempts=5
failure_threshold=3
delay=1

# track state
state='up'
failures=0
echo "Pinging ${ip} forever (CTRL-C / SIGTERM to quit)..."
while true ; do
  if ping -c 1 $ip >/dev/null 2>&1 ; then
    # ping succeeded
    if [ "$failures" -gt "0" ] ; then let failures-=1 ; fi
  else # ping failed
    if [ "$failures" -lt "$track_attempts" ] ; then let failures+=1 ; fi
  fi
  # echo "Failures in the last $track_attempts attempts: $failures"
  # detect state change...
  if [ "$failures" -gt "$failure_threshold" ] ; then
    if [ "$state" == 'up' ] ; then
      echo "Connection has gone down at $(date +'%Y-%m-%d %H:%M:%S %Z')!"
      state='down'
    fi
  else
    if [ "$state" == 'down' ] ; then
      echo "Connection has come up at $(date +'%Y-%m-%d %H:%M:%S %Z')!"
      state='up'
    fi
  fi
  sleep $delay
done