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| #!/usr/bin/env bash | |
| set -e | |
| watch_dns(){ | |
| HOST=$1 | |
| DNS_SERVER=${2:-"8.8.8.8"} | |
| OLD_IP="$(dig +short "$HOST")" | |
| echo "$(date) Starting to watch $HOST for changes from \"$OLD_IP\" as tracked by ${DNS_SERVER}" | |
| while true; do | |
| DNS_LATENCY_PRE_CHECK=$(ping -c 1 "$DNS_SERVER" | ggrep -P '\d+\sbytes' | ggrep -Pow '\d+\.\d+\sms') | |
| IP="$(dig "@${DNS_SERVER}" +short "$HOST")" | |
| DNS_LATENCY_POST_CHECK=$(ping -c 1 "$DNS_SERVER" | ggrep -P '\d+\sbytes' | ggrep -Pow '\d+\.\d+\sms') | |
| if [[ $IP == "$OLD_IP" ]]; then | |
| sleep 1 | |
| continue | |
| fi | |
| echo "$(date) IP from \"$OLD_IP\" to \"$IP\", DNS latency before check: $DNS_LATENCY_PRE_CHECK, DNS latency post check: $DNS_LATENCY_POST_CHECK" | |
| OLD_IP=$IP | |
| sleep 1 | |
| done | |
| } | |
| watch_dns "$1" "${2:-"8.8.8.8"}" | |
| # example call: | |
| # watch_dns dynamodb.us-east-2.amazonaws.com | |
| # or | |
| # watch_dns google.com 1.1.1.1 |
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