# More an O/S question, but I would like to ask here

**URL:** https://discourse.nodered.org/t/more-an-o-s-question-but-i-would-like-to-ask-here/38763
**Category:** General
**Created:** [8 January 2021 00:12 UTC](https://discourse.nodered.org/t/more-an-o-s-question-but-i-would-like-to-ask-here/38763 "2021-01-08T00:12:02Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)
#### Post date: [8 January 2021 00:12 UTC](https://discourse.nodered.org/t/more-an-o-s-question-but-i-would-like-to-ask-here/38763/1 "2021-01-08T00:12:03Z")

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I have a RasPi and a USB stick plugged into it for logging.  
A 128 MG stick. (Yeah: old)

I have `fs-ops` installed and I run a command daily to indicate the used/available space on the stick.

Today the machine has been rebooted (though it has been done before other times and this not happen) and I was looking at the use. `0`. !!??

This is the part of the flow which is used to get the usage:

```auto
[{"id":"386cfd91.ae4962","type":"inject","z":"39ea4ac5.b46c1e","name":"Start / test","props":[{"p":"payload","v":"","vt":"date"},{"p":"topic","v":"","vt":"string"}],"repeat":"","crontab":"","once":true,"onceDelay":"2","topic":"","payload":"","payloadType":"date","x":620,"y":4480,"wires":[["e6ba5de5.61847"]]},{"id":"e6ba5de5.61847","type":"Drives","z":"39ea4ac5.b46c1e","name":"","x":570,"y":4560,"wires":[["20499dc9.358b92","e6bea6bd.2aa96"]]},{"id":"20499dc9.358b92","type":"function","z":"39ea4ac5.b46c1e","name":"","func":"var used = msg.payload[8].capacity;\nmsg.payload = used * 100;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":720,"y":4560,"wires":[["2a48360d.1985b2","bdc13e1a.224c","951f3bcc.f09ab8","1a7b1fd6.f0e248"]]}]

```

(Given there is another input to do this daily.)

You can see the `function` node extracts `[8]`'s message for the USB stick.

This had to be modified as it was `[9]`.

_Who_ is changing it form `[8]` to `[9]`?

Anyone got a suggestion how I can make the flow _track_ it if it changes where in the array it is?

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<div class="post-metadata">

### Author: ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)
#### Post date: [9 March 2021 00:12 UTC](https://discourse.nodered.org/t/more-an-o-s-question-but-i-would-like-to-ask-here/38763/2 "2021-03-09T00:12:05Z")

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