The REST API can be used by automation tools and is also used by the Apex CLI, for which we will now provide a few examples.
Assuming the example application is still running, let's attach with the CLI and collect some details from it:
apex@apex-sandbox:~$ apex Apex CLI 3.5.0 14.03.2017 @ 08:14:36 UTC rev: d86f0da branch: d86f0da78b7be9bffb30b73c5fa762711dbce379 apex> list-apps {"apps": [{ "startTime": "2017-03-22 04:42:04 +0000", "id": 2, "name": "MyFirstApplication", "state": "RUNNING", "trackingUrl": "http:\/\/apex- sandbox:8088\/proxy\/application_1490156780107_0001\/", "finalStatus": "UNDEFINED", "tags": [] }]} 1 active, total ...