condition_from_expression

Create a new condition.

⚙️ Compatible targets: Linux

Parameters

NameDocumentation
conditionThe condition prefix.

This parameter is required.
expressionThe expression evaluated to create the condition (use 'any' to always evaluate to true).

This parameter is required.

Example

method: condition_from_expression
params:
  condition: VALUE
  expression: VALUE

Documentation

This method evaluates an expression, and produces a ${condition}_true or a ${condition}_false condition depending on the result of the expression evaluation:

  • This method always result with a success outcome status
  • If the evaluation results in a "defined" state, this will define a ${condition}_true condition,
  • If the evaluation results in an "undefined" state, this will produce a ${condition}_false condition.

Calling this method with a condition expression transforms a complex expression into a single condition.

The created condition is global to the agent.

Example

If you want to check if a condition evaluates to true, like checking that you are on Monday, 2am, on RedHat systems, you can use the following policy

condition_from_expression("backup_time", "Monday.redhat.Hr02")

The method will define:

  • In any case:
    • condition_from_expression_backup_time_kept
    • condition_from_expression_backup_time_reached
  • And:
    • backup_time_true if the system is a RedHat like system, on Monday, at 2am.
    • backup_time_false if the system not a RedHat like system, or it's not Monday, or it's not 2am
    • no extra condition if the expression is invalid (cannot be parsed)
Notes:

Rudder will automatically "canonify" the given Condition prefix at execution time, which means that all non [a-zA-Z0-9_] characters will be replaced by an underscore.