Cache systemctl list-unit-files to avoid repeated calls

Add get_unit_files() and unit_file_exists() helper functions
that cache the output of systemctl list-unit-files. This
avoids running the same command multiple times when checking
for node_exporter and hwmon.timer unit files.

#6

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

proxDoc.sh

@@ -18,6 +18,8 @@ LOGFILE="${PROXDOC_LOGFILE:-}"
 ###################
 # Disk list cache - populated on first use
 DISK_LIST=""
+# Unit files cache - populated on first use
+UNIT_FILES=""
 
 ###################
 # Pattern Constants
@@ -128,6 +130,20 @@ get_disk_list() {
     echo "$DISK_LIST"
 }
 
+# Get systemctl unit files with caching
+get_unit_files() {
+    if [[ -z "$UNIT_FILES" ]]; then
+        UNIT_FILES=$(systemctl list-unit-files 2>/dev/null)
+    fi
+    echo "$UNIT_FILES"
+}
+
+# Check if a unit file exists (uses cached data)
+unit_file_exists() {
+    local unit_name="$1"
+    get_unit_files | grep -q "$unit_name"
+}
+
 # Efficient process wait with optional spinner
 # Usage: wait_for_process $pid [delay]
 # Uses kill -0 instead of ps -p for efficiency
@@ -531,7 +547,7 @@ get_node_exporter_status() {
         else
             log_message warn "Port 9100 not listening"
         fi
-    elif systemctl list-unit-files 2>/dev/null | grep -q node_exporter; then
+    elif unit_file_exists node_exporter; then
         log_message warn "Node Exporter is installed but not running"
         echo -e "Start with: systemctl start node_exporter"
     else
@@ -546,7 +562,7 @@ get_hwmon_status() {
         systemctl list-timers hwmon.timer --no-pager 2>/dev/null
         echo -e "\n${GREEN}Last Run:${NC}"
         journalctl -u hwmon.service -n 3 --no-pager 2>/dev/null || true
-    elif systemctl list-unit-files 2>/dev/null | grep -q hwmon.timer; then
+    elif unit_file_exists hwmon.timer; then
         log_message warn "hwmon timer is installed but not active"
         echo -e "Enable with: systemctl enable --now hwmon.timer"
     else