Ruby executable in YAML

Question

I have a sample yaml file(abc.yaml) like this:

entity1:
  condition: "created_at >= #{Date.today - 3.months}"

I want to read this condition from YAML in Ruby as :

"created_at >= 2015-03-02"

But when I do

YAML.load_file('abc.yaml')["entity1"]["condition"]

I get:

"created_at >= \#{Date.today - 3.months}"

Please let me know how to work around this.

Answer 1

The safer option would be to only convert known data from a pre-determined format. Or use something cool like settingslogic https://github.com/settingslogic/settingslogic. It uses ERB-style formatting to load settings, so you get some built in safety.

eg:

defaults: &defaults
  cool:
    saweet: nested settings
  neat_setting: 24
  awesome_setting: <%= "Did you know 5 + 5 = #{5 + 5}?" %>

Answer 2

Do this only if you're absolutely sure nobody can change your yaml file to inject something harmful:

condition = YAML.load_file('abc.yaml')["entity1"]["condition"]
condition = eval "\"#{condition}\""