# Logstash: filter a dynamic field in the log line

**URL:** <https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492>\
**Category:** Logstash\
**Created:** [September 1, 2016, 5:45am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492 "2016-09-01T05:45:21Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Dilesh\_Verma](https://avatars.discourse-cdn.com/v4/letter/d/4da419/32.png) [@Dilesh\_Verma](https://discuss.elastic.co/u/Dilesh_Verma)\
**Post date:** [September 1, 2016, 5:45am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/1 "2016-09-01T05:45:21Z")

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In the below input, we need to filter out “COUNT\_XXX123=1,SUCCESS\_XXX123=1” even if we don’t have “sellerId=XXX123” field available.  
Input:

> OtherMessages1=1,sellerId=XXX123,COUNT\_XXX123=1,SUCCESS\_XXX123=1,OtherMessages2=2

Filter:

```
filter {
        kv {
                field_split => ","
        }
        mutate {
                remove_field => ["COUNT_%{WORD}", "SUCCESS_%{sellerId}"]
        }
}

```

In above case it is only filtering SUCCESS\_XXX123 but not COUNT\_XXX123.

---

<div class="post-metadata">

**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 1, 2016, 6:31am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/2 "2016-09-01T06:31:09Z")

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> ```
> remove_field => ["COUNT_%{WORD}", "SUCCESS_%{sellerId}"]
> 
> ```

This needs to be:

```
 remove_field => ["COUNT_%{sellerId}", "SUCCESS_%{sellerId}"]

```

You might also find the prune filter useful.

---

<div class="post-metadata">

**Author:** ![Dilesh\_Verma](https://avatars.discourse-cdn.com/v4/letter/d/4da419/32.png) [@Dilesh\_Verma](https://discuss.elastic.co/u/Dilesh_Verma)\
**Post date:** [September 1, 2016, 6:47am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/3 "2016-09-01T06:47:07Z")

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Thanks for you reply, I wanted to ask if we don't have "sellerId" field available can we just remove all fields like "COUNT\_\*"?

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<div class="post-metadata">

**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 1, 2016, 7:15am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/4 "2016-09-01T07:15:41Z")

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Did you look at the prune filter as I suggested?

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<div class="post-metadata">

**Author:** ![Dilesh\_Verma](https://avatars.discourse-cdn.com/v4/letter/d/4da419/32.png) [@Dilesh\_Verma](https://discuss.elastic.co/u/Dilesh_Verma)\
**Post date:** [September 1, 2016, 11:11am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/5 "2016-09-01T11:11:32Z")

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Yes, prune filter with blacklist\_names worked for this, Thanks a lot for your help!

```
 prune {
                    blacklist_names => ["SUCCESS_[A-Za-z0-9]*", "COUNT_[A-Za-z0-9]*" ]
  }
```

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 4:40am UTC](https://discuss.elastic.co/t/logstash-filter-a-dynamic-field-in-the-log-line/59492/6 "2017-07-06T04:40:27Z")

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