# Dynamic field fetching
**URL:** https://discuss.elastic.co/t/dynamic-field-fetching/201584
**Category:** Logstash
**Created:** [September 30, 2019, 7:12am UTC](https://discuss.elastic.co/t/dynamic-field-fetching/201584 "2019-09-30T07:12:07Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@amanpradhan](https://discuss.elastic.co/u/amanpradhan)
#### Post date: [September 30, 2019, 7:12am UTC](https://discuss.elastic.co/t/dynamic-field-fetching/201584/1 "2019-09-30T07:12:07Z")
I have a field "msg\_string" in my logs which has multiple fields saparated by tilda "~"
e.g. msg\_string =firstname~lasname~city~hobby~marks ...
position of fields firstname,lastname are at index 0 and 1
the position of field city is not fixed i can appear anywhere in msg\_string hence i am using look up with city names. I am using split to saparate out fields in msg\_string and extract firstname and lastname
I have a file with city names for look up i want to add a field name city using lookup file
how to do it please help.
split =\> ["msg\_string","~"]
add\_field =\> {"firstname"=\> "%{[msg\_string][0]}"}
add\_field =\> {"lastname"=\> "%{[msg\_string][1]}"}
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### Author:  [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)
#### Post date: [September 30, 2019, 7:19am UTC](https://discuss.elastic.co/t/dynamic-field-fetching/201584/2 "2019-09-30T07:19:09Z")
Can you not use a cab filter with “~” as a separator or perhaps a dissect filter?
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [October 28, 2019, 7:26am UTC](https://discuss.elastic.co/t/dynamic-field-fetching/201584/3 "2019-10-28T07:26:36Z")
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