write file conditionally

[Lawrence Griffiths]

Hi I've searched for this.

I've got a file write wired to a function and only want to write when a certain state is true.

I can't see a way doing this?

I'm currently changing the file name when condition is false so can preserve correct data.

But this means an unnecessary write each time I get an input from a sensor.

Thanks in advance for any help.

Lawrence

[Edward Vielmetti]

Lawrence,

Can you put another node downstream from your function (like a switch) that takes care of the conditional? E.g. if your function returns msg.payload and also msg.flag with a result from 0 or 1 and you only want to write when msg.flag is 1, you could have a switch that is wired to your file write function only when the flag is set.

Two screen captures attached!

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[Andrew Lindsay]

Can you not use a function node with 2 outputs. One out up is to a file node, the second to a debug or other non file node.

In your function you would set the output msg to be null for first value if you didn't want to write the output to a file. When you need to write you have the first value as the msg and the second as null. This way you could direct the flow around a file node if needed.

Not got access to NR at present so can't verify exact details.

Regards

Andrew

[Lawrence Griffiths]

Edward/Andrew thanks for the prompt replies.

I'm still in newbi mode and not thinking in a node-red like way.

I keep forgetting you can have multiple in/out.

Lawrence

[Dave C-J]

Yes - see multiple outputs section of http://nodered.org/docs/writing-functions.html

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regards

Dave Conway-Jones