# Can't parse custom grok expression responsible for extracting file extension

**URL:** <https://discuss.elastic.co/t/cant-parse-custom-grok-expression-responsible-for-extracting-file-extension/201247>\
**Category:** Logstash\
**Created:** [September 26, 2019, 1:57pm UTC](https://discuss.elastic.co/t/cant-parse-custom-grok-expression-responsible-for-extracting-file-extension/201247 "2019-09-26T13:57:27Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![saif3r](https://avatars.discourse-cdn.com/v4/letter/s/49beb7/32.png) [@saif3r](https://discuss.elastic.co/u/saif3r)\
**Post date:** [September 26, 2019, 1:57pm UTC](https://discuss.elastic.co/t/cant-parse-custom-grok-expression-responsible-for-extracting-file-extension/201247/1 "2019-09-26T13:57:28Z")

</div>

Hello,

I'm using custom grok pattern to extract file extension from field called **message**  
Here's the configuration snippet:

```
filter {
	grok {
		match => {
			"message" => "(?<file_ext>(\.[^.\\/:*?"<>|\r\n]+$))"
		}
	}}

```

Here's **message** field content sample:

> asdasdas.txt asdsadsa asdsa.pdf

Here's Grok Debugger screenshot:  
 ![Grok_Debugger](https://us1.discourse-cdn.com/elastic/original/3X/c/8/c8482b40aca985e4b74cdcb4a37a31ee14fe2c85.png)

And here's the error message:

> [ERROR] 2019-09-26 16:01:21.865 [Converge PipelineAction::Reload] agent - Failed to execute action {:id=\>:main, :action\_type=\>LogStash::ConvergeResult::FailedAction, :message=\>"Expected one of #, {, } at line 39, column 43 (byte 698) after filter {\r\n\tgrok {\r\n\t\tmatch =\> {\r\n\t\t\t"message" =\> "(?\<file\_ext\>(\.[^.\\/:\*?"", :backtrace=\>["/usr/share/logstash/logstash-core/lib/logstash/compiler.rb:41:in `compile_imperative'", "/usr/share/logstash/logstash-core/lib/logstash/compiler.rb:49:in `compile\_graph'", "/usr/share/logstash/logstash-core/lib/logstash/compiler.rb:11:in `block in compile_sources'", "org/jruby/RubyArray.java:2577:in `map'", "/usr/share/logstash/logstash-core/lib/logstash/compiler.rb:10:in `compile_sources'", "org/logstash/execution/AbstractPipelineExt.java:151:in `initialize'", "org/logstash/execution/JavaBasePipelineExt.java:47:in `initialize'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline_action/reload.rb:37:in `execute'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:325:in `block in converge\_state'"]}

Any clues what might be the cause for this error? I'm surprised since Debugger shows a positive result.

---

<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:** [September 26, 2019, 2:01pm UTC](https://discuss.elastic.co/t/cant-parse-custom-grok-expression-responsible-for-extracting-file-extension/201247/2 "2019-09-26T14:01:30Z")

</div>

You have an unquoted double quote in the middle of your double quoted string. Try using

```
'(?<file_ext>(\.[^.\\/:*?"<>|\r\n]+$))'
```

---

<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:** [October 24, 2019, 2:03pm UTC](https://discuss.elastic.co/t/cant-parse-custom-grok-expression-responsible-for-extracting-file-extension/201247/3 "2019-10-24T14:03:53Z")

</div>

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