# How to extract a substring

**URL:** <https://discuss.elastic.co/t/how-to-extract-a-substring/281578>\
**Category:** Logstash\
**Created:** [August 16, 2021, 5:19pm UTC](https://discuss.elastic.co/t/how-to-extract-a-substring/281578 "2021-08-16T17:19:49Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![dvrla](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@dvrla](https://discuss.elastic.co/u/dvrla)\
**Post date:** [August 16, 2021, 5:19pm UTC](https://discuss.elastic.co/t/how-to-extract-a-substring/281578/1 "2021-08-16T17:19:49Z")

</div>

Hi,  
I would like to extract the value of a cookie from an HTTP request but up until now I can´t make it work.

I´m trying to get from a request field like this

```
GET /trading/css/main.css?version=4.4.0 HTTP/1.1, Host: example.com, Connection: keep-alive, sec-ch-ua: %22Chromium%22;v=%2292%22, %22 Not A;Brand%22;v=%2299%22, %22Google Chrome%22;v=%2292%22, sec-ch-ua-mobile: ?0, User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36, Accept: text/css,*/*;q=0.1, Sec-Fetch-Site: same-origin, Sec-Fetch-Mode: no-cors, Sec-Fetch-Dest: style, Accept-Encoding: gzip, deflate, br, Accept-Language: en-US,en;q=0.9, Cookie: _imp_di_pc_=AeiKv2AAAAAA%2Fe2%2Bl0tSpWzh1QMWVNiq; _imp_apg_r_=%7B%22diA%22%3A%22AeiKv2AAAAAA%2Fe2%2Bl0tSpWzh1QMWV f5did=SELECT+IF%28+USER%28%29+LIKE+%27root%40%25%27%2C+BENCHMARK%28100000%2CSHA1%28%27test%27%29%29%2C+%27false%27%29%3B; TS017a1cec=01b48180428042621a43fb9eb5a96afbcffd42e83ec7ebd222f4ed66d4621184363ff53bfcb5059689d9253d43f19b1336ef6f5d0d8e94453021ae1e7789599141b36f7c52

```

the cookie value of _imp\_apg\_r_. For this I got this grok filter  
match =\> {  
request =\> [(?\<deviceid\_raw\>_imp\_apg\_r_=[^;]\*) ]  
}  
Can anyone point me to the right direction?

Thanks in advance!!

---

<div class="post-metadata">

**Author:** ![Badger](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/badger/32/25190_2.png) [@Badger](https://discuss.elastic.co/u/Badger)\
**Post date:** [August 16, 2021, 7:05pm UTC](https://discuss.elastic.co/t/how-to-extract-a-substring/281578/2 "2021-08-16T19:05:16Z")

</div>

> [@dvrla](#):
>
> _imp\_apg\_r_ =

You appear to be missing the underscores around the name. I would use

```
grok { match => { "message" => "_imp_apg_r_=(?<deviceid_raw>[^;]*)" } }

```

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<div class="post-metadata">

**Author:** ![dvrla](https://avatars.discourse-cdn.com/v4/letter/d/85e7bf/32.png) [@dvrla](https://discuss.elastic.co/u/dvrla)\
**Post date:** [August 17, 2021, 7:10am UTC](https://discuss.elastic.co/t/how-to-extract-a-substring/281578/3 "2021-08-17T07:10:56Z")

</div>

Thank you!! Desperation makes you blind 🙂

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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:** [September 14, 2021, 7:11am UTC](https://discuss.elastic.co/t/how-to-extract-a-substring/281578/4 "2021-09-14T07:11:24Z")

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