file_from_template_mustache

Build a file from a mustache template.

⚙️ Compatible targets: Linux, Windows

Parameters

NameDocumentation
source_templateSource file containing a template to be expanded (absolute path on the target node).

This parameter is required.
pathDestination file (absolute path on the target node).

This parameter is required.

Outcome conditions

You need to replace ${path} with its actual canonified value.

  • ✅ Ok: file_from_template_${path}_ok
    • ☑️ Already compliant: file_from_template_${path}_kept
    • 🟨 Repaired: file_from_template_${path}_repaired
  • ❌ Error: file_from_template_${path}_error

Example

method: file_from_template_mustache
params:
  source_template: VALUE
  path: VALUE

Documentation

See file_from_template_type for general documentation about templates usage.

Syntax

Mustache is a logic-less templating language, available in a lot of languages, and used for file templating in Rudder. The mustache syntax reference is https://mustache.github.io/mustache.5.html. The Windows implementation follows the standard, the Unix one is a bit richer as describe below.

We will here describe the way to get agent data into a template. Ass explained in the general templating documentation, we can access various data in a mustache template.

The main specificity compared to standard mustache syntax of prefixes in all expanded values:

  • classes to access conditions
  • vars to access all variables
Classes

Here is how to display content depending on conditions definition:

{{#classes.my_condition}}
   content when my_condition is defined
{{/classes.my_condition}}

{{^classes.my_condition}}
   content when my_condition is *not* defined
{{/classes.my_condition}}

Note: You cannot use condition expressions here.

Scalar variable

Here is how to display a scalar variable value (integer, string, ...), if you have defined variable_string("variable_prefix", "my_variable", "my_value"):

{{{vars.variable_prefix.my_variable}}}

We use the triple {{{ }}} to avoid escaping html entities.

Iteration

Iteration is done using a syntax similar to scalar variables, but applied on container variables.

  • Use {{#vars.container}} content {{/vars.container}} to iterate
  • Use {{{.}}} for the current element value in iteration
  • Use {{{key}}} for the key value in current element
  • Use {{{.key}}} for the key value in current element (Linux only)
  • Use {{{@}}} for the current element key in iteration (Linux only)

To iterate over a list, for example defined with:

variable_iterator("variable_prefix", "iterator_name", "a,b,c", ",")

Use the following file:

{{#vars.variable_prefix.iterator_name}}
{{{.}}} is the current iterator_name value
{{/vars.variable_prefix.iterator_name}}

Which will be expanded as:

a is the current iterator_name value
b is the current iterator_name value
c is the current iterator_name value

To iterate over a container defined by the following json file, loaded with variable_dict_from_file("variable_prefix", "dict_name", "path"):

{
   "hosts": [
       "host1",
       "host2"
   ],
   "files": [
       {"name": "file1", "path": "/path1", "users": [ "user1", "user11" ] },
       {"name": "file2", "path": "/path2", "users": [ "user2" ] }
   ],
   "properties": {
       "prop1": "value1",
       "prop2": "value2"
   }
}

Use the following template:

{{#vars.variable_prefix.dict_name.hosts}}
{{{.}}} is the current hosts value
{{/vars.variable_prefix.dict_name.hosts}}

# will display the name and path of the current file
{{#vars.variable_prefix.dict_name.files}}
{{{name}}}: {{{path}}}
{{/vars.variable_prefix.dict_name.files}}
# Lines below will only be properly rendered in unix Nodes
# will display the users list of each file
{{#vars.variable_prefix.dict_name.files}}
{{{name}}}:{{#users}} {{{.}}}{{/users}}
{{/vars.variable_prefix.dict_name.files}}


# will display the current properties key/value pair
{{#vars.variable_prefix.dict_name.properties}}
{{{@}}} -> {{{.}}}
{{/vars.variable_prefix.dict_name.properties}}

Which will be expanded as:

host1 is the current hosts value
host2 is the current hosts value

# will display the name and path of the current file
file1: /path1
file2: /path2

# Lines below will only be properly rendered in unix Nodes
# will display the users list of each file
file1: user1 user11
file2: user2

# will display the current properties key/value pair
prop1 -> value1
prop2 -> value2

Note: You can use {{#-top-}} ... {{/-top-}} to iterate over the top level container.

System variables

Some sys dict variables (like sys.ipv4) are also accessible as string, for example:

  • ${sys.ipv4} gives 54.32.12.4
  • $[sys.ipv4[ethO]} gives 54.32.12.4
  • $[sys.ipv4[eth1]} gives 10.45.3.2

These variables are not accessible as dict in the templating data, but are represented as string:

  • ipv4 is a string variable in the sys dict with value 54.32.12.4
  • ipv4[ethO] is a string variable in the sys dict with value 54.32.12.4
  • ipv4 is not accessible as a dict in the template

To access these value, use the following syntax in your mustache templates:

{{{vars.sys.ipv4[eth0]}}}