# How to remove part of name in multiple fields with Ruby in logstash?

**URL:** <https://discuss.elastic.co/t/how-to-remove-part-of-name-in-multiple-fields-with-ruby-in-logstash/254263>\
**Category:** Logstash\
**Created:** [November 4, 2020, 11:39am UTC](https://discuss.elastic.co/t/how-to-remove-part-of-name-in-multiple-fields-with-ruby-in-logstash/254263 "2020-11-04T11:39:01Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![alytkowski](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@alytkowski](https://discuss.elastic.co/u/alytkowski)\
**Post date:** [November 5, 2020, 7:16am UTC](https://discuss.elastic.co/t/how-to-remove-part-of-name-in-multiple-fields-with-ruby-in-logstash/254263/5 "2020-11-05T07:16:51Z")

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> [@Badger](#):
>
> ```auto
> event.to_hash.each { |k,v|
> if k =~ "^prometheus.metrics.ems"
> newK = k.sub(/^prometheus.metrics.ems/, "")
> event.remove(k)
> event.set(newK, v)
> end
> }
> 
> ```

Unfortunately this gives out below error in the logs:  
[ERROR][logstash.filters.ruby][main] Ruby exception occurred: type mismatch: String given

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