Fix detection of plugdev group for Linux users

OpenBCI_GUI/Extras.pde

@@ -158,6 +158,34 @@ public boolean isElevationNeeded(String path) {
     }
     return result;
 }
+/**
+* Determines if user is in elevated group (plugdev).  
+*
+* @return <code>true</code> if user is in group plugdev, <code>false</code> otherwise.
+ */
+public boolean isInElevatedGroup() {
+    boolean result = true;
+    if (isLinux()) {
+        try {
+            String command = "groups";
+            Process p = Runtime.getRuntime().exec(command);
+            p.waitFor();
+            InputStream stdIn = p.getInputStream();
+            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(stdIn));
+            String[] values = bufferedReader.readLine().split(" ");
+            for (int idx=0; idx<values.length; idx++) {
+                result = values[idx].equals("plugdev");
+                if (result) {
+                    break;
+                }
+            }
+        } catch (Exception e) {
+            return false;
+        }
+    }
+    return result;
+}
+
 /**
 * Determine if user has administrative privileges.
 *

OpenBCI_GUI/OpenBCI_GUI.pde

@@ -497,8 +497,8 @@ void delayedSetup() {
     //Apply GUI-wide settings to front end at the end of setup
     guiSettings.applySettings();
 
-    if (!isAdminUser() || isElevationNeeded()) {
-        outputError("OpenBCI_GUI: This application is not being run with Administrator access. This could limit the ability to connect to devices or read/write files.");
+    if (!isInElevatedGroup() && (!isAdminUser() || isElevationNeeded())) {
+        outputError("OpenBCI_GUI: This application is not being run with Administrator access or user is not member of plugdev group. This could limit the ability to connect to devices or read/write files.");
     }
 }