Concatenate and string

General
1

I have an environment variable named ip-address and can assign access it using ${ip-address}.

For example I assign it to a dashboard text node label or use it in a change node to set a message field.

I use it because the rig I have moves around and it used with different networks so I change the variable and it is reflected on may nodes.

But I would like to be able to simplify matters even further.

If I set ip-address ro just the first three octets, ie 192.168.1. then I can use it to change further nodes.

For example, I have three nodes that are set to 192.168.1.11, 192.168.1.12, 192.168.1.13.

I could then assign something like ${ip-address} + "1", ${ip-address} + "2", ${ip-address} + "3" to set them accordingly.

Rather than change 3 (or more) places, then I change just one.

Unfortunately I cannot figure out the syntax, the + "1" does not work. Is it possible to do?

2

As per the docs:

This only works if it replaces the entire property - it cannot be used to substitute just part of the value. For example, it is not possible to use CLIENT-${HOST} .

However, if the field where you are using it is a TypedInput (where it has the $ env selection) then it is possible e.g. ${ip-address}1


The only other option is to use a change node, function node, or other node to do the string concatenation.

Example Function:

msg.ip = env.get('ip-address') + '1'
return msg
3

The change node appears to accept a typed input (see test1 below) but then adding suffixes, whether with no concatenate characters or a plus symbol does not work.

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(Note that I am only assigning to a flow variable because it is very quick and easy to monitor the resulting values)

4

Try using the env type input

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As Steve noted

5

Try using the env type input

Thank you, that works in a change node perfectly.

How can I also make it work in a standard text field that accepts typed inputs?

I tried ${ip-address} which is fine but ${ip-address}1 or even ${ip-address}${another-var} both fail.

6

You cannot

Instead, you would need to do it in a function or change node using JSONata

7

or
in a template node

{{env.ip_prefix}}1
8

As per the docs

Ah, I missed that!

So, I am trying another tactic, because it better suits my workflow (I get the details that way): an array of addresses, ie ["192.168.1.1","192.168.1.2","192.168.1.3"] which I assign as a JSON string

image

Trouble is trying to access the elements, ${ip-address[0]} was my guess, which is incorrect. How far off is my syntax?

9

You would not us env input.
You would use msg input
msg. ip-address[0]

If the json is in a env var, then first set it to a msg var.
So would require two rules.
set
msg. ìp-address
to
$ ip-address

then
set
msg. ip-address
to
msg. ip-address[0]

Or
with one rule use JSONata input
set
msg. ip-address
to
J: $env("ip-address")[0]

10

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