Fix duplicate process detection - more robust tasklist parsing

Author: Magnus

src/elmocut.py

@@ -18,62 +18,63 @@
     app = QApplication(argv)
     icon = ElmoCut.processIcon(app_icon)
 
-    # Check if Npcap is installed
+    # Check if Npcap is installed (Windows only)
     if not npcap_exists():
         if msg_box('ArpCut', 'Npcap is not installed\n\nClick OK to download',
                     MsgIcon.CRITICAL, icon, Buttons.OK | Buttons.CANCEL) == Buttons.OK:
             goto(NPCAP_URL)
+        exit(1)
 
     # Check if another ArpCut process is running
-    elif duplicate_elmocut():
+    if duplicate_elmocut():
         msg_box('ArpCut', 'ArpCut is already running!', MsgIcon.WARN, icon)
+        exit(1)
 
     # Run the GUI
-    else:
-        migrate_settings_file()
-        repair_settings()
-        GUI = ElmoCut()
-        GUI.show()
-        GUI.resizeEvent()
-        
-        # Initialize scanner and ensure interface is valid
+    migrate_settings_file()
+    repair_settings()
+    GUI = ElmoCut()
+    GUI.show()
+    GUI.resizeEvent()
+    
+    # Initialize scanner and ensure interface is valid
+    GUI.scanner.init()
+    if GUI.scanner.iface.name == 'NULL':
+        # Try to get a valid interface
+        from tools.utils import get_default_iface
+        GUI.scanner.iface = get_default_iface()
         GUI.scanner.init()
-        if GUI.scanner.iface.name == 'NULL':
-            # Try to get a valid interface
-            from tools.utils import get_default_iface
-            GUI.scanner.iface = get_default_iface()
-            GUI.scanner.init()
-        
-        # Ensure "Me" and "Router" are added immediately
-        try:
-            GUI.scanner.add_me()
-            GUI.scanner.add_router()
-            GUI.showDevices()  # Show at least "Me" and "Router" on startup
-        except Exception as e:
-            GUI.log(f'Warning: Could not initialize local devices: {e}', 'orange')
-        
-        GUI.scanner.flush_arp()
+    
+    # Ensure "Me" and "Router" are added immediately
+    try:
+        GUI.scanner.add_me()
+        GUI.scanner.add_router()
+        GUI.showDevices()  # Show at least "Me" and "Router" on startup
+    except Exception as e:
+        GUI.log(f'Warning: Could not initialize local devices: {e}', 'orange')
+    
+    GUI.scanner.flush_arp()
 
-        # On macOS/Linux when not root, avoid ARP scan (requires /dev/bpf) and use Ping scan
-        try:
-            import os
-            is_posix = (os.name == 'posix')
-            is_root = (getattr(os, 'geteuid', lambda: 0)() == 0)
-        except Exception:
-            is_posix, is_root = False, True
+    # On macOS/Linux when not root, avoid ARP scan (requires /dev/bpf) and use Ping scan
+    try:
+        import os
+        is_posix = (os.name == 'posix')
+        is_root = (getattr(os, 'geteuid', lambda: 0)() == 0)
+    except Exception:
+        is_posix, is_root = False, True
 
-        if is_posix and not is_root:
-            GUI.log('Running without root: using Ping Scan', 'orange')
-            GUI.ScanThread_Starter(scan_type=1)
+    if is_posix and not is_root:
+        GUI.log('Running without root: using Ping Scan', 'orange')
+        GUI.ScanThread_Starter(scan_type=1)
+    else:
+        # Only check connection if interface is valid
+        if GUI.scanner.iface.name != 'NULL':
+            GUI.scanEasy()
         else:
-            # Only check connection if interface is valid
-            if GUI.scanner.iface.name != 'NULL':
-                GUI.scanEasy()
-            else:
-                GUI.log('No network interface found. Please check your network connection.', 'red')
+            GUI.log('No network interface found. Please check your network connection.', 'red')
 
-        GUI.UpdateThread_Starter()
-        # Bring window to top on startup
-        GUI.activateWindow()
-        #GUI.scanner.print_report()
-        exit(app.exec_())
+    GUI.UpdateThread_Starter()
+    # Bring window to top on startup
+    GUI.activateWindow()
+    #GUI.scanner.print_report()
+    exit(app.exec_())

src/tools/utils_gui.py

@@ -35,8 +35,18 @@ def duplicate_elmocut():
     Check if there is more than 1 instance of ArpCut running
     """
     if sys.platform.startswith('win'):
-        tasklist = terminal('tasklist')
-        return tasklist.lower().count('arpcut.exe') > 1
+        try:
+            tasklist = terminal('tasklist')
+            if not tasklist:
+                return False
+            # Count actual process entries (each on its own line)
+            count = 0
+            for line in tasklist.lower().split('\n'):
+                if 'arpcut.exe' in line:
+                    count += 1
+            return count > 1
+        except Exception:
+            return False
     # TODO: Implement PID/file lock if needed for macOS
     return False