Added commands to list paths.
Added protection against bad input on some command-lines.
diff --git a/cli/src/main/java/org/onlab/onos/cli/net/DevicePortsListCommand.java b/cli/src/main/java/org/onlab/onos/cli/net/DevicePortsListCommand.java
index 03fc555..8750424 100644
--- a/cli/src/main/java/org/onlab/onos/cli/net/DevicePortsListCommand.java
+++ b/cli/src/main/java/org/onlab/onos/cli/net/DevicePortsListCommand.java
@@ -42,7 +42,12 @@
                 printDevice(service, device);
             }
         } else {
-            printDevice(service, service.getDevice(deviceId(uri)));
+            Device device = service.getDevice(deviceId(uri));
+            if (device == null) {
+                error("No such device %s", uri);
+            } else {
+                printDevice(service, device);
+            }
         }
         return null;
     }