# Backspace(\\b) doesn't work with the gsub filter

**URL:** <https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191>\
**Category:** Logstash\
**Created:** [May 2, 2018, 6:38am UTC](https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191 "2018-05-02T06:38:15Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![jvayao](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jvayao/32/30730_2.png) [@jvayao](https://discuss.elastic.co/u/jvayao)\
**Post date:** [May 2, 2018, 6:38am UTC](https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191/1 "2018-05-02T06:38:16Z")

</div>

Version: 6.x  
Operating System: Any  
Backspace(\b) doesn't work with the gsub filter:

Config:

```
mutate {
	gsub => [
		"Data","\u0000","",
		"Data","\u0001","",
		"Data","\u0002","",
		"Data","\u0003","",
		"Data","\u0004","",
		"Data","\u0005","",
		"Data","\u0006","",
		"Data","\f","",
		"Data","\a","",
		"Data","\b",""
	] 
}
json {
	source => "Data"
}

```

Log:  
[2018-03-13T14:43:55,298][WARN][logstash.filters.json] Error parsing json {:source=\>"Data", :raw=\>"{"bid":"00015","platform":"AndroidPhone","brand":"HUAWEI","device":"ALP-TL00","os":"8.0.0","hid":"23e63ec86d7a48d7NDF7N17C14000402866215033164432","name":"com.android.haitong","ver":"81","token":"","appkey":"BiiilRwAYsKdk828aRMb8ktOXfaTPWAZo1tibfkrkXQ=","sdk\_ver":"1.1.19.11","timestamp":"1520913226940"}\b\b\b\b\b\b\b\b", :exception=\>#\<LogStash::Json::ParserError: Illegal character ((CTRL-CHAR, code 8)): only regular white space (\r, \n, \t) is allowed between tokens at [Source: (byte[])"{"bid":"00015","platform":"AndroidPhone","brand":"HUAWEI","device":"ALP-TL00","os":"8.0.0","hid":"23e63ec86d7a48d7NDF7N17C14000402866215033164432","name":"com.android.haitong","ver":"81","token":"","appkey":"BiiilRwAYsKdk828aRMb8ktOXfaTPWAZo1tibfkrkXQ=","sdk\_ver":"1.1.19.11","timestamp":"1520913"; line: 1, column: 306]\>}

---

<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:** [May 2, 2018, 7:02am UTC](https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191/2 "2018-05-02T07:02:40Z")

</div>

Here's a list of the supported escape sequences: [https://www.elastic.co/guide/en/logstash/current/configuration-file-structure.html](https://www.elastic.co/guide/en/logstash/current/configuration-file-structure.html)

---

<div class="post-metadata">

**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [May 2, 2018, 7:07am UTC](https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191/3 "2018-05-02T07:07:40Z")

</div>

> [@magnusbaeck](#):
>
> [Structure of a pipeline | Logstash Reference [8.11] | Elastic](https://www.elastic.co/guide/en/logstash/current/configuration-file-structure.html)

I believe `\b` matches a [word boundary](https://www.regular-expressions.info/wordboundaries.html) and not backspace.

---

<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:** [May 30, 2018, 7:07am UTC](https://discuss.elastic.co/t/backspace-b-doesnt-work-with-the-gsub-filter/130191/4 "2018-05-30T07:07:41Z")

</div>

Closed on May 30, 2018, 7:07am UTC

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