Add new field with value from grok filter

[Automation_Scripts]

Hi all,

I need to add a value to a field from a variable within a grok filter.

filter {
    grok { 
      match => [ "message", "(?<ts>(.*?))\t(?<uids>(.*?))" ]    
 }
    mutate { add_field => { "container_id" => "%{uids}" } }
}

The field is created but the value is not taken into consideration it simply puts the string %{uids}.
How should I add the value from this grok variable to a field?

Thank you!

[elasticforme (Sachin)]

this is because you have %{uid} not set from grok pattern.

otherwise code looks correct

[Automation_Scripts]

something was caching badly. worked like a charm after restart.