efficiency, don't apt update again if already done

updatemirror.sh

@@ -2,6 +2,10 @@
 
 set -euo pipefail
 
+function apt_update_if_stale () {
+    [ -z "$(find /var/lib/apt/lists -type f -mmin -30 2>/dev/null)" ] && apt-get update
+}
+
 function main () {
     # check for ubuntu only
     if ! grep -qi '^ID=ubuntu' /etc/os-release; then
@@ -25,15 +29,25 @@ function main () {
     find /etc/apt/sources.list.d/ -type f -exec \
       sed -i "s|archive\.ubuntu\.com|us.ubuntu.com|g" {} +
 
+    apt_update_if_stale
+    apt install -y jq curl
+
     echo "Detecting actual country..." > /dev/stderr
 
-    apt update && apt install -y curl jq
     IPINFO="$(curl -s ipinfo.io)"
+
     if [ -z "$IPINFO" ]; then
         echo "Failed to get IP info" > /dev/stderr
         exit 1
     fi
+
     COUNTRYCODE="$(jq .country -r <<< "$IPINFO")"
+
+    if [[ -z "$COUNTRYCODE" ]]; then
+        echo "Failed to get country code" > /dev/stderr
+        exit 1
+    fi
+
     echo "IP geolocated as country: $COUNTRYCODE" > /dev/stderr
 
     if ! grep -qE 'http(s)?://us\.archive\.ubuntu\.com/' /etc/apt/sources.list.d/*; then
@@ -42,7 +56,7 @@ function main () {
     fi
 
     if [[ "$COUNTRYCODE" == "US" ]]; then
-        echo "Mirror already set to  US, nothing to do" > /dev/stderr
+        echo "Mirror already set to US, nothing to do" > /dev/stderr
         exit 0
     fi