# Concatenation in Ruby Code **URL:** \ **Category:** Logstash\ **Created:** [September 6, 2017, 5:05pm UTC](https://discuss.elastic.co/t/concatenation-in-ruby-code/99614 "2017-09-06T17:05:16Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![paul1243](https://avatars.discourse-cdn.com/v4/letter/p/e99b99/32.png) [@paul1243](https://discuss.elastic.co/u/paul1243)\ **Post date:** [September 6, 2017, 5:05pm UTC](https://discuss.elastic.co/t/concatenation-in-ruby-code/99614/1 "2017-09-06T17:05:17Z")
Hi - Could someone please let me know how to concatenate a couple of strings in Ruby code over Logstash. Below is the snippet of code: for i in 0..arr.size - 1 cpu\_hash = [cpu\_hash, {'CPU#{i}' =\> arr[i].to\_i}].reduce &:merge end Am creating a hash with the array of values. But I wanted to add the 'i' value in the key field along with the CPU word. (So it creates unique key value) In Ruby it works like this "CPU#{i}", not sure how does it work in Logstash. Please let me know. Thanks ! ---
**Author:** ![magnusbaeck](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/magnusbaeck/32/44943_2.png) [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)\ **Post date:** [September 7, 2017, 5:29am UTC](https://discuss.elastic.co/t/concatenation-in-ruby-code/99614/2 "2017-09-07T05:29:55Z")
> In Ruby it works like this “CPU#{i}”, not sure how does it work in Logstash. It works exactly the same in Logstash, but the string needs to be double-quoted. Such string-interpolation doesn't take place in single-quoted strings like in your example. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [October 5, 2017, 5:30am UTC](https://discuss.elastic.co/t/concatenation-in-ruby-code/99614/3 "2017-10-05T05:30:11Z")
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