more robust public ip look up.

4-public-ip.sh

@@ -1,8 +1,44 @@
 #!/bin/bash
 
-# works consistently if you specify the -4 to force IPv4
-dig -4 +short A myip.opendns.com @resolver1.opendns.com
+# there are a few different ways to resolve public-ip,
+# keep trying until we get a result
 
-#curl --fail --silent --show-error https://ipinfo.io/ip
-#echo ""
+# dig
+if [[ -n $(command -v "dig") ]]; then
+    # via opendns
+    address=$(dig "@resolver1.opendns.com" -4 "myip.opendns.com" "A" "+short")
+    if [[ "$?" -ne "0" ]]; then
+        # dig was unsuccessful
+        echo "$address" 1>&2
+        address=""
+    fi
+fi
+
+# curl
+if [[ -z "$address" ]] && [[ -n $(command -v "curl") ]]; then
+    # via ipinfo.io
+    address=$(curl -4 --fail --silent --show-error "https://ipinfo.io/ip")
+
+    if [[ -z "$address" ]]; then
+        # via google
+        address=$(curl -4 --fail --silent --show-error "https://domains.google.com/checkip")
+    fi
+fi
+
+# wget
+if [[ -z "$address" ]] && [[ -n $(command -v "wget") ]]; then
+    # via ipinfo.io
+    address=$(wget -4 --quiet --output-document - "https://ipinfo.io/ip")
+
+    if [[ -z "$address" ]]; then
+        # via google
+        address=$(wget -4 --quiet --output-document - "https://domains.google.com/checkip")
+    fi
+fi
+
+if [[ -n "$address" ]]; then
+    echo "$address"
+else
+    echo 'Tried everything, unable to resolve IP address.' 1>&2
+fi