1 files changed, 89 insertions, 0 deletions
diff --git a/dyndns.bash b/dyndns.bash
new file mode 100755
index 0000000..91261ec
--- /dev/null
+++ b/dyndns.bash
@@ -0,0 +1,89 @@
+#! /bin/bash  
+
+# Work with DigitalOcean api to update "A" record for a domain.
+# Store DigitalOcean API token in file : DIGITALOCEAN_TOKEN 
+# Store domain to be updated in file : DIGITALOCEAN_DOMAIN 
+
+SCRIPT="${BASH_SOURCE[0]}"
+SCRIPT_DIR=$(builtin cd "${SCRIPT%/*}" && pwd )
+SCRIPT_NAME=${SCRIPT##*/}
+
+REPEAT_CHECK_DIR=$HOME/repeat_check
+REPEAT_CHECK=$REPEAT_CHECK_DIR/$SCRIPT_NAME # file to save argument in if successful
+
+DIGITALOCEAN_DOMAIN=`cat $SCRIPT_DIR/DIGITALOCEAN_DOMAIN`
+DIGITALOCEAN_TOKEN=`cat $SCRIPT_DIR/DIGITALOCEAN_TOKEN`
+
+# Get IP from command line if available.  Otherwise use curl to get public IP.
+IP=""
+if [ "$#" == "1" ]; then
+    IP=$1
+else
+    IP=`curl -4 icanhazip.com 2> /dev/null` 
+fi
+
+# If $IP does not look like a valid address then complain and exit.
+# For regular expression, thank you to : https://tecadmin.net/shell-script-validate-ipv4-addresses/
+if ! [[ $IP =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
+    echo Invalid IP address format: $IP
+    exit
+fi
+
+get_a_record_ids() {
+    curl -X GET \
+      -H "Content-Type: application/json" \
+      -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
+      "https://api.digitalocean.com/v2/domains/$DIGITALOCEAN_DOMAIN/records" 2> /dev/null | jq '.domain_records |  map(select(.type == "A" and .name == "@")) | map(.id) | .[]'
+}
+
+add_a_record() {
+    echo adding new A record for $DIGITALOCEAN_DOMAIN with value : $IP
+    curl -X POST \
+      -H "Content-Type: application/json" \
+      -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
+      -d "{\"type\":\"A\"         \
+          ,\"name\":\"@\"         \
+          ,\"data\":\"$IP\"       \
+          ,\"priority\":null      \
+          ,\"port\":null          \
+          ,\"ttl\":1800           \
+          ,\"weight\":null        \
+          ,\"flags\":null         \
+          ,\"tag\":null           \
+          }"                      \
+      "https://api.digitalocean.com/v2/domains/$DIGITALOCEAN_DOMAIN/records" > /dev/null 2>&1
+}
+
+delete_record_by_id() {
+    echo deleting existing A record for $DIGITALOCEAN_DOMAIN
+    curl -X DELETE \
+      -H "Content-Type: application/json" \
+      -H "Authorization: Bearer $DIGITALOCEAN_TOKEN" \
+      "https://api.digitalocean.com/v2/domains/$DIGITALOCEAN_DOMAIN/records/$1" > /dev/null 2>&1
+}
+
+replace_a_record() {
+    for id in `get_a_record_ids`; do
+        delete_record_by_id $id
+    done
+
+    add_a_record
+}
+
+
+# exit if previous successful call was with same argument
+if [[ -e $REPEAT_CHECK ]]; then
+    PREVIOUS_IP=`cat $REPEAT_CHECK`
+    if [[ "$IP" ==  "$PREVIOUS_IP" ]]; then
+        echo previous update was also with argument: \"$IP\"  so exiting now to avoid duplicate work.
+        exit
+    fi
+fi
+
+# attempt to replace A record and, if successful, save arguments to check against next time
+if replace_a_record $IP; then
+    # if successful then save arguments.
+    echo update worked so saving arguments \"$IP\" in $REPEAT_CHECK
+    mkdir -p $REPEAT_CHECK_DIR
+    echo "$IP" > $REPEAT_CHECK
+fi