only update if IP changed

Signed-off-by: Jeff Billimek <jeff@billimek.com>

dyndns.sh

@@ -20,6 +20,7 @@ while ( true ); do
         -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
         $dns_list)
     record_id=$(echo $domain_records| jq ".domain_records[] | select(.type == \"A\" and .name == \"$NAME\") | .id")
+    record_data=$(echo $domain_records| jq -r ".domain_records[] | select(.type == \"A\" and .name == \"@\") | .data")
     
     test -z $record_id && die "No record found with given domain name!"
 
@@ -28,13 +29,15 @@ while ( true ); do
     url="$dns_list/$record_id"
 
     if [[ -n $ip ]]; then
-        echo "Sending data=$data to url=$url"
+        if [[ "$ip" != "$record_data" ]]; then
+            echo "existing DNS record address ($record_data) doesn't match current IP ($ip), sending data=$data to url=$url"
 
-        curl -s -X PUT \
-            -H "Content-Type: application/json" \
-            -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
-            -d "$data" \
-            "$url" &> /dev/null
+            curl -s -X PUT \
+                -H "Content-Type: application/json" \
+                -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
+                -d "$data" \
+                "$url" &> /dev/null
+        fi
     else
         echo "IP wasn't retrieved within allowed interval. Will try $sleep_interval seconds later.."
     fi