test NTP accuracy of local Starlink dish vs. ntp.org

check-ntp.sh

#!/bin/bash

########
# test NTP accuracy of local Starlink dish vs. ntp.org
########

# List of NTP servers; Starlink is first, followed by ntp.org
SERVERS=("192.168.100.1" "us.pool.ntp.org")
COUNT=10  # Number of times to run sntp per server
SUMMARY_FILE=$(mktemp)  # Store summary results

for SERVER in "${SERVERS[@]}"; do
    TEMP_FILE=$(mktemp)
    echo -e "\nRunning sntp $COUNT times against $SERVER..."

    for i in $(seq 1 $COUNT); do
        OUTPUT=$(sntp -sS "$SERVER" 2>/dev/null)
        echo "$OUTPUT" >> "$TEMP_FILE"
        echo "[$i/$COUNT] $OUTPUT"
        sleep 0.5  # Adjust sleep time if needed
    done

    echo -e "\nSummary for $SERVER:"
    awk -v server="$SERVER" '{
        adj=$1 * 1000;  # Convert to milliseconds
        sum+=adj; sum_sq+=adj*adj; count+=1;
    }
    END {
        mean=sum/count;
        stddev=sqrt(sum_sq/count - mean*mean);
        printf "%s: Mean adjustment: %.4f ms | Standard deviation: %.4f ms\n", server, mean, stddev;
    }' "$TEMP_FILE" >> "$SUMMARY_FILE"

    rm "$TEMP_FILE"
done

echo -e "\n========================="
echo "Final Summary (Comparison)"
echo "========================="
cat "$SUMMARY_FILE"

# Find most stable and most accurate server (compatibility fix)
BEST_SERVER=$(awk 'NR==1 || $9 < min {min=$9; best=$1} END {print best}' "$SUMMARY_FILE")

MOST_ACCURATE_SERVER=$(awk 'NR==1 || ($4 < 0 ? -$4 : $4) < min {min=($4 < 0 ? -$4 : $4); accurate=$1} END {print accurate}' "$SUMMARY_FILE")

echo -e "\nMost Stable Server (Lowest Std Dev): $BEST_SERVER"
echo "Most Accurate Server (Closest to 0 Mean Adjustment): $MOST_ACCURATE_SERVER"

rm "$SUMMARY_FILE"