I made a flow for Windows PC's that checks for updates, but if you change the file-path to fit your system it will work.
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test","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payloadType":"str","x":790,"y":480,"wires":[["9a682b8e06cbc47e"]]},{"id":"e90c1af7ea9b30d8","type":"comment","z":"b6faf7d8.b5efa8","name":"How often to check","info":"","x":110,"y":480,"wires":[]},{"id":"e9e2d19cccb1c1d0","type":"comment","z":"b6faf7d8.b5efa8","name":"Send to a notification flow","info":"","x":1410,"y":540,"wires":[]},{"id":"57e5bc1434255e11","type":"comment","z":"b6faf7d8.b5efa8","name":"replace location for your system","info":"","x":350,"y":480,"wires":[]},{"id":"05cf562f0b953db6","type":"function","z":"b6faf7d8.b5efa8","name":"chomp left","func":"msg.payload = msg.payload.substr(1, +Infinity)\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":950,"y":400,"wires":[["77873223bd69beae"]]},{"id":"b850824df4055e47","type":"comment","z":"b6faf7d8.b5efa8","name":"No need to send this one","info":"","x":1410,"y":380,"wires":[]}]
By default it checks every 3 days, and then pipes a message out to a notification flow if an update is available.