# Logstash extract part of field

**URL:** <https://discuss.elastic.co/t/logstash-extract-part-of-field/304312>\
**Category:** Logstash\
**Created:** [May 10, 2022, 7:17am UTC](https://discuss.elastic.co/t/logstash-extract-part-of-field/304312 "2022-05-10T07:17:31Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![d.silwon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/d.silwon/32/65853_2.png) [@d.silwon](https://discuss.elastic.co/u/d.silwon)\
**Post date:** [May 10, 2022, 7:17am UTC](https://discuss.elastic.co/t/logstash-extract-part-of-field/304312/1 "2022-05-10T07:17:31Z")

</div>

Dears,

ELK in version 7.16.3

What is the best way to extract part of mapped xml field to new field?

```auto
  if "app1xml" in [tags] {
  xml {
    source => "message"
    store_xml => false
    force_array => false
    xpath => [
      "/log//msg/field[@id='2']/@value", "app.source_field",

    ]
  }
  }

```

example field looks like:

```auto
      <field id="2" value="5350621360940215"/>

```

and I need only four first signs.

```auto
5350

```

Best Regards,  
Dan

---

<div class="post-metadata">

**Author:** ![adrianfusco](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/adrianfusco/32/111798_2.png) [@adrianfusco](https://discuss.elastic.co/u/adrianfusco)\
**Post date:** [May 10, 2022, 7:54am UTC](https://discuss.elastic.co/t/logstash-extract-part-of-field/304312/2 "2022-05-10T07:54:09Z")

</div>

Hello,

Can you try using `substring`?

```auto
"substring(/log//msg/field[@id='2']/@value, 0, 4)", "app.source_field"

```

---

<div class="post-metadata">

**Author:** ![d.silwon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/d.silwon/32/65853_2.png) [@d.silwon](https://discuss.elastic.co/u/d.silwon)\
**Post date:** [May 10, 2022, 8:14am UTC](https://discuss.elastic.co/t/logstash-extract-part-of-field/304312/3 "2022-05-10T08:14:09Z")

</div>

@adrianfusco

Works well. Thanks a lot.

---

<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:** [June 7, 2022, 8:14am UTC](https://discuss.elastic.co/t/logstash-extract-part-of-field/304312/4 "2022-06-07T08:14:42Z")

</div>

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