Change filename for write Node dynamical and string change handling

General
1

So far, so good—I managed to do it in one day, but I'm a complete novice and come from LabView, where I can do something like this in 10 minutes... but anyway. Here's an example: my question is, is there any way to do this without a function node, especially when handling strings for the file name?
function:
msg.filename = '/home/rr/Dokumente/Logger/testloggera_' + flow.get("NowDate") + '.txt';
return msg;

[
    {
        "id": "3ad48c473fea5513",
        "type": "function",
        "z": "80ea8d142ccb0bd4",
        "name": "setze filename mit NowDate neu zusammen",
        "func": "  msg.filename = '/home/rr/Dokumente/Logger/testloggera_' + flow.get(\"NowDate\") + '.txt';\n    return msg;\n",
        "outputs": 1,
        "timeout": 0,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 850,
        "y": 500,
        "wires": [
            [
                "b37f712221ebfe5f",
                "1dfaff9af10ddb0e",
                "806a9b21564b40f0"
            ]
        ]
    }


]

Bildschirmfoto vom 2025-10-17 17-36-45
Bildschirmfoto vom 2025-10-17 17-36-451920×1040 223 KB

2

You could use Jsonata in a change node

image
image1164×295 13.6 KB

[{"id":"0d1266049d9698cf","type":"change","z":"d14258870cbe9738","name":"","rules":[{"t":"set","p":"filename","pt":"msg","to":"'/home/rr/Dokumente/Logger/testloggera_' & $flowContext(\"NowDate\") & '.txt'","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":290,"y":225,"wires":[["6526a6d0ad6fbad0"]]}]
1 Like
3

Yes i now :sweat_smile: but is it without any scripting possible?

4

You could use mustache syntax in a template node but NowDate would have to be a message property rather than a flow context variable. (Why are you using a flow context variable anyway?)

image
image774×452 18.7 KB

5

One of the big mysteries for me is the use of templates and what a mustach is—what a funny name. I've only shown an excerpt of my project here. The variable flow.NowDate is used elsewhere as a decision maker...
But thanks again, I'm coming from LabView where everything works without scripting! But LV has its quirks too... me hoppe is/was also NR is script free, :wink:

6

The name mustache clearly derives from it's use in this (admittedly uncommon) smiley :-{)

A really big mystery is how the ! came to be called Bang!

I've never heard of LabView. How would you concatenate the strings in that?

This is not a very Node-red approach, though of course it is possible to code it like this.
A flow context variable can be changed at any time by the arrival of a new message.
The Node-red approach would be to generate the value and attach it as a message property. Then the value is passed along the flow* and is unaffected by a new input

* Most nodes follow the rule of passing on such message properties unaffected. Some contrib nodes fail to do this.

7

You can do this in the change node without scripting, but why not use JSONata direct in file write node?

example of change node with no scripting

[{"id":"0d1266049d9698cf","type":"change","z":"613df62afc8a16bf","name":"","rules":[{"t":"set","p":"filename","pt":"msg","to":"/home/rr/Dokumente/Logger/testloggera_*#*.txt","tot":"str"},{"t":"set","p":"NowDate","pt":"msg","to":"NowDate","tot":"flow"},{"t":"change","p":"filename","pt":"msg","from":"*#*","fromt":"str","to":"NowDate","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":380,"y":80,"wires":[["e99af74c636b45c0"]]}]