# Strange error with gsub

**URL:** <https://discuss.elastic.co/t/strange-error-with-gsub/133827>\
**Category:** Logstash\
**Created:** [May 30, 2018, 8:42am UTC](https://discuss.elastic.co/t/strange-error-with-gsub/133827 "2018-05-30T08:42:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![br14nb0](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/br14nb0/32/28814_2.png) [@br14nb0](https://discuss.elastic.co/u/br14nb0)\
**Post date:** [May 30, 2018, 8:42am UTC](https://discuss.elastic.co/t/strange-error-with-gsub/133827/1 "2018-05-30T08:42:18Z")

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I have my mutate config  
mutate {  
gsub =\> [  
"service","\x7f\\",""]  
}

I want to replace "DEL" string with NULL. But look likes it misunderstands with my escape.

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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:** [May 30, 2018, 6:51pm UTC](https://discuss.elastic.co/t/strange-error-with-gsub/133827/2 "2018-05-30T18:51:42Z")

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That escape sequence isn't supported.

[https://www.elastic.co/guide/en/logstash/6.3/configuration-file-structure.html#\_escape\_sequences](https://www.elastic.co/guide/en/logstash/6.3/configuration-file-structure.html#_escape_sequences)

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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:** [June 27, 2018, 6:51pm UTC](https://discuss.elastic.co/t/strange-error-with-gsub/133827/3 "2018-06-27T18:51:50Z")

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