add separate flag for NbserverListApp json list output

notebook/notebookapp.py

@@ -389,18 +389,28 @@ class NbserverListApp(JupyterApp):
     description=_("List currently running notebook servers.")
     
     flags = dict(
+        jsonlist=({'NbserverListApp': {'jsonlist': True}},
+              _("Produce machine-readable JSON list output.")),
         json=({'NbserverListApp': {'json': True}},
-              _("Produce machine-readable JSON output.")),
+              _("Produce machine-readable JSON object on each line of output.")),
     )
     
+    jsonlist = Bool(False, config=True,
+          help=_("If True, the output will be a JSON list of objects, one per "
+                 "active notebook server, each with the details from the "
+                 "relevant server info file."))
     json = Bool(False, config=True,
           help=_("If True, each line of output will be a JSON object with the "
-                  "details from the server info file."))
+                  "details from the server info file. For a JSON list output, "
+                  "see the NbserverListApp.jsonlist configuration value"))
 
     def start(self):
         serverinfo_list = list(list_running_servers(self.runtime_dir))
-        if self.json:
-            print(json.dumps(serverinfo_list))
+        if self.jsonlist:
+            print(json.dumps(serverinfo_list, indent=2))
+        elif self.json:
+            for serverinfo in serverinfo_list:
+                print(json.dumps(serverinfo))
         else:
             print("Currently running servers:")
             for serverinfo in serverinfo_list: