best practice for accessing facts from ERB template?

[Tim Mooney]

All-

Is there a canonical way to access hierarchical facts like
$facts['os']['release']['major'] or $facts['networking']['fqdn'] from
an ERB template? I've been searching for a best practice answer and
so far I've only found conflicting advice.

I'm specifically asking about facts, not variables from other
classes/scope.

I've found recommendations suggesting each of these:

<%= $facts['os']['release']['major'] %>
<%= @facts['os']['release']['major'] %>
<%= $facts.dig("os","release","major") %>
<%= @facts.dig("os","release","major") %>

as well as suggestions to use scope[] or scope.lookupvar() or use dotted
fact notation, but I haven't figured out how to make either the scope or
dotted route work in ERB.

The "$facts.dig()" suggestion comes directly from the Puppet 8
compatibility wiki entry:

https://github.com/puppetlabs/puppet/wiki/Puppet-8-Compatibility

but it doesn't seem to work for me. Using the @facts.dig() does, though.

So far the two methods I've found that work are

<%= @facts['os']['release']['major'] %>

or

<%= @facts.dig("os","release","major") %>

Is there any reason to prefer one over the other, or some other method
that I haven't found yet?

I don't want to convert our existing ERB templates to EPP.

I know I could set local variables in a puppet class like

$osreleasemajor = $facts['os']['release']['major']
$fqdn = $facts['networking']['fqdn']

and then access the local variables in the template, but if possible I
would like to avoid that approach.

Thanks,

Tim
--
Tim Mooney Tim.M...@ndsu.edu
Enterprise Computing & Infrastructure /
Division of Information Technology / 701-231-1076 (Voice)
North Dakota State University, Fargo, ND 58105-5164

[Dirk Heinrichs]

Am Dienstag, dem 29.07.2025 um 20:56 -0500 schrieb 'Tim Mooney' via Puppet Users:

I've found recommendations suggesting each of these:

        <%= $facts['os']['release']['major'] %>

        <%= @facts['os']['release']['major'] %>

        <%= $facts.dig("os","release","major") %>

        <%= @facts.dig("os","release","major") %>

The "$" variants are non-sense. Use "@" to access variables defined OUTSIDE the template (@somevar or @facts[]) and omit it from variables defined INSIDE the template.

as well as suggestions to use scope[] or scope.lookupvar() or use

"scope[]" MUST be used to access variables defined in a different class, for example if a template is used in a sub-class, but the variables it uses are defined in the main class. The classical example for this is the separation of "myclass" into "init.pp" (which defines the parameters), "install.pp", "config.pp" (where a config file is generated from a template) and "service.pp".

The notation in this case is

<%= scope['myclass::param'] =>

or, if the parameter or variable is an array or hash map

<%= scope['myclass::param'][<index or key>] =>

HTH...

Dirk

-- 

Dirk Heinrichs

Senior Systems Engineer, Delivery Pipeline

OpenText ™ Discovery | Recommind

Phone: +49 2226 15966 18

Email: dhei...@opentext.com

Website: www.recommind.de

Recommind GmbH, Von-Liebig-Straße 1, 53359 Rheinbach

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