From e92690a7111d1cd27399c3515bbd472624db205f Mon Sep 17 00:00:00 2001
From: Dani Guardiola <hi@daniguardio.la>
Date: Mon, 12 Jan 2026 05:19:12 +0100
Subject: [PATCH] add support for updating multiple domains

---
 README.md          |  19 +++++--
 dns-sync.sh        | 123 ++++++++++++++++++++++++++++++++++++---------
 dns.config.example |  11 ++--
 3 files changed, 120 insertions(+), 33 deletions(-)

diff --git a/README.md b/README.md
index c6ce5c0..97be655 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # Vercel Dynamic DNS
 
 Simple script for exposing a local server with [Vercel DNS](https://vercel.com/docs/custom-domains).
-It runs on CRON, checking the current IP address and updating DNS records for your domain.
+It runs on CRON, checking the current IP address and updating DNS records for your domains.
 
 ## Installation
 
@@ -12,19 +12,30 @@ It runs on CRON, checking the current IP address and updating DNS records for yo
 5. Open the cron settings using the command `crontab -e`
 6. Add the following line to the cron job: `*/15 * * * * /path-to/vercel-ddns/dns-sync.sh`
 
+### Configuration
+
+Set these values inside `dns.config`:
+
+- `VERCEL_TOKEN`: Personal token from https://vercel.com/account/tokens
+- `DOMAINS`: Comma-separated list of fully qualified domains you want to keep in sync. Examples: `example.com`, `api.example.com, www.example.com`, `foo.bar.example.com, example.com`. The script treats the last two labels as the apex domain (e.g. `foo.bar.example.com` → apex `example.com`, subdomain `foo.bar`).
+
 ## Usage example
 
 ```sh
-# Creating
+# Creating (multiple domains supported)
 ➜  ./dns-sync.sh
 Updating IP: x.x.x.x
-Record for SUBDOMAIN does not exist. Creating...
+Processing api.example.com
+Record for api.example.com does not exist. Creating...
+Processing example.com
+Record for example.com already exists (id: rec_xxxxxxxxxxxxxxxxxxxxxxxx). Updating...
 🎉 Done!
 
 # Updating
 ➜  ./dns-sync.sh
 Updating IP: x.x.x.x
-Record for SUBDOMAIN already exists (id: rec_xxxxxxxxxxxxxxxxxxxxxxxx). Updating...
+Processing api.example.com
+Record for api.example.com already exists (id: rec_xxxxxxxxxxxxxxxxxxxxxxxx). Updating...
 🎉 Done!
 ```
 
diff --git a/dns-sync.sh b/dns-sync.sh
index a25b74d..a35ba3b 100755
--- a/dns-sync.sh
+++ b/dns-sync.sh
@@ -18,16 +18,21 @@ get_current_ip() {
   echo $ip
 }
 
-# Function to check if subdomain exists
+# Function to check if subdomain exists for a given domain
 check_subdomain_exists() {
-  local subdomain="$1"
+  local domain_name="$1"
+  local subdomain="$2"
   local response
-  response=$(curl -sX GET "https://api.vercel.com/v4/domains/$DOMAIN_NAME/records" \
+  response=$(curl -sX GET "https://api.vercel.com/v4/domains/$domain_name/records" \
     -H "Authorization: Bearer $VERCEL_TOKEN" \
     -H "Content-Type: application/json")
 
   local record_id
-  record_id=$(echo "$response" | jq -r ".records[] | select(.name == \"$subdomain\") | .id")
+  if [[ -z "$subdomain" ]]; then
+    record_id=$(echo "$response" | jq -r '.records[] | select((.name == "") or (.name == null)) | .id')
+  else
+    record_id=$(echo "$response" | jq -r ".records[] | select(.name == \"$subdomain\") | .id")
+  fi
   if [[ -n "$record_id" ]]; then
     # Return record ID if exists
     echo "$record_id"
@@ -39,15 +44,21 @@ check_subdomain_exists() {
 
 # Updates dns record
 update_dns_record() {
-  local ip="$1"
-  local record_id="$2"
+  local domain_name="$1"
+  local subdomain="$2"
+  local ip="$3"
+  local record_id="$4"
+  local host_display="$domain_name"
+  if [[ -n "$subdomain" ]]; then
+    host_display="$subdomain.$domain_name"
+  fi
   local response
   response=$(curl -sX PATCH "https://api.vercel.com/v1/domains/records/$record_id" \
     -H "Authorization: Bearer $VERCEL_TOKEN" \
     -H "Content-Type: application/json" \
     -d '{
       "comment": "vercel-ddns",
-      "name": "'$SUBDOMAIN'",
+      "name": "'$subdomain'",
       "type": "A",
       "value": "'$ip'",
       "ttl": 60
@@ -57,21 +68,27 @@ update_dns_record() {
   if [[ "$response" == *"error"* ]]; then
     local error_message
     error_message=$(echo "$response" | jq -r '.error.message')
-    echo "⚠️ Error updating DNS record: $error_message"
-    exit 1
+    echo "⚠️ Error updating DNS record for $host_display: $error_message"
+    return 1
   fi
 }
 
 # Creates dns record
 create_dns_record() {
-  local ip="$1"
+  local domain_name="$1"
+  local subdomain="$2"
+  local ip="$3"
+  local host_display="$domain_name"
+  if [[ -n "$subdomain" ]]; then
+    host_display="$subdomain.$domain_name"
+  fi
   local response
-  response=$(curl -sX POST "https://api.vercel.com/v4/domains/$DOMAIN_NAME/records" \
+  response=$(curl -sX POST "https://api.vercel.com/v4/domains/$domain_name/records" \
     -H "Authorization: Bearer $VERCEL_TOKEN" \
     -H "Content-Type: application/json" \
     -d '{
       "comment": "vercel-ddns",
-      "name": "'$SUBDOMAIN'",
+      "name": "'$subdomain'",
       "type": "A",
       "value": "'$ip'",
       "ttl": 60
@@ -81,23 +98,81 @@ create_dns_record() {
   if [[ "$response" == *"error"* ]]; then
     local error_message
     error_message=$(echo "$response" | jq -r '.error.message')
-    echo "⚠️ Error creating DNS record: $error_message"
-    exit 1
+    echo "⚠️ Error creating DNS record for $host_display: $error_message"
+    return 1
+  fi
+}
+
+# Split a fully qualified domain into apex and subdomain parts
+split_domain() {
+  local full_domain="$1"
+  local IFS='.'
+  read -r -a parts <<< "$full_domain"
+  local total_parts=${#parts[@]}
+  if (( total_parts < 2 )); then
+    echo "⚠️ Invalid domain: $full_domain" >&2
+    return 1
+  fi
+
+  local apex
+  apex="${parts[$((total_parts - 2))]}.${parts[$((total_parts - 1))]}"
+
+  local subdomain_parts=()
+  if (( total_parts > 2 )); then
+    subdomain_parts=("${parts[@]:0:$((total_parts - 2))}")
+  fi
+
+  local subdomain=""
+  if (( ${#subdomain_parts[@]} > 0 )); then
+    local IFS='.'
+    subdomain="${subdomain_parts[*]}"
   fi
+
+  echo "$apex|$subdomain"
 }
 
-# Get current IP
+# Clean and split the DOMAINS list into an array
+IFS=',' read -r -a DOMAIN_ENTRIES <<< "$DOMAINS"
+IFS=$' \t\n'
+
+# Get current IP once for all domains
 ip=$(get_current_ip)
 echo "Updating IP: $ip"
 
-# Check if subdomain exists
-record_id=$(check_subdomain_exists "$SUBDOMAIN")
-if [[ -n "$record_id" ]]; then
-  echo "Record for $SUBDOMAIN already exists (id: $record_id). Updating..."
-  update_dns_record "$ip" "$record_id"
-else
-  echo "Record for $SUBDOMAIN does not exist. Creating..."
-  create_dns_record "$ip"
-fi
+for raw_domain in "${DOMAIN_ENTRIES[@]}"; do
+  domain_trimmed=$(echo "$raw_domain" | xargs)
+
+  if [[ -z "$domain_trimmed" ]]; then
+    continue
+  fi
+
+  split_result=$(split_domain "$domain_trimmed") || continue
+  domain_name=${split_result%%|*}
+  subdomain=${split_result#*|}
+
+  # Log which host we are processing
+  if [[ -z "$subdomain" ]]; then
+    echo "Processing apex $domain_name"
+  else
+    echo "Processing $subdomain.$domain_name"
+  fi
+
+  record_id=$(check_subdomain_exists "$domain_name" "$subdomain")
+  if [[ -n "$record_id" ]]; then
+    if [[ -z "$subdomain" ]]; then
+      echo "Record for $domain_name already exists (id: $record_id). Updating..."
+    else
+      echo "Record for $subdomain.$domain_name already exists (id: $record_id). Updating..."
+    fi
+    update_dns_record "$domain_name" "$subdomain" "$ip" "$record_id"
+  else
+    if [[ -z "$subdomain" ]]; then
+      echo "Record for $domain_name does not exist. Creating..."
+    else
+      echo "Record for $subdomain.$domain_name does not exist. Creating..."
+    fi
+    create_dns_record "$domain_name" "$subdomain" "$ip"
+  fi
+done
 
 echo "🎉 Done!"
diff --git a/dns.config.example b/dns.config.example
index 90cc8e0..322f1ce 100644
--- a/dns.config.example
+++ b/dns.config.example
@@ -3,8 +3,9 @@
 # Get the token from https://vercel.com/account/tokens
 VERCEL_TOKEN=""
 
-# Domain name (e.g. example.com)
-DOMAIN_NAME=""
-
-# Subdomain to update (note: use an empty string for the root record)
-SUBDOMAIN=""
+# Comma-separated list of full domains (with or without subdomains)
+# Examples:
+#   "example.com"
+#   "api.example.com, www.example.com"
+#   "foo.bar.example.com, example.com"
+DOMAINS=""