# Compare two fields
**URL:** https://discuss.elastic.co/t/compare-two-fields/110088
**Category:** Logstash
**Created:** [December 4, 2017, 4:45am UTC](https://discuss.elastic.co/t/compare-two-fields/110088 "2017-12-04T04:45:18Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@pope843](https://discuss.elastic.co/u/pope843)
#### Post date: [December 4, 2017, 4:45am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/1 "2017-12-04T04:45:18Z")
Hello Guys,
Just want to know if below condition will work or possible?
filter {
ruby {
code =\> "
event.set('dateko', Time.now.strftime('%Y-%m-%d'))
"
}
if [dateko] not in [message] {
.......
}
}
---
### Author:  [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)
#### Post date: [December 4, 2017, 6:24am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/2 "2017-12-04T06:24:04Z")
Syntax-wise that looks fine. Why ask when you can try it out?
---
### Author:  [@pope843](https://discuss.elastic.co/u/pope843)
#### Post date: [December 4, 2017, 6:29am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/3 "2017-12-04T06:29:17Z")
thanks Magnus, sorry i have a running config in production. just want to add that condition. I've tested it now and it seemed to work. Also it's available on the docu online
[https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html](https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html)
Btw, I have this ruby code
```
ruby {
code => "
event.set('datemo', DateTime.yesterday.strftime('%Y-%m-%d'))
"
}
```
But i've encountered this error on logstash logs, could you help me pls what was wrong here.
[2017-12-04T06:20:50,922][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method `yesterday' for DateTime:Class [2017-12-04T06:20:50,926][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method`yesterday' for DateTime:Class
[2017-12-04T06:20:50,927][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method `yesterday' for DateTime:Class [2017-12-04T06:20:50,928][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method`yesterday' for DateTime:Class
[2017-12-04T06:20:50,929][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method `yesterday' for DateTime:Class [2017-12-04T06:20:50,931][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method`yesterday' for DateTime:Class
[2017-12-04T06:20:50,934][ERROR][logstash.filters.ruby] Ruby exception occurred: undefined method `yesterday' for DateTime:Class
---
### Author:  [@magnusbaeck](https://discuss.elastic.co/u/magnusbaeck)
#### Post date: [December 4, 2017, 7:06am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/4 "2017-12-04T07:06:53Z")
> sorry i have a running config in production. just want to add that condition.
You need to have a usable test environment.
> Ruby exception occurred: undefined method `yesterday' for DateTime:Class
Well, the standard DateTime class doesn't have a `yesterday` method. I don't know Ruby well enough to give a good countersuggestion.
---
### Author:  [@pope843](https://discuss.elastic.co/u/pope843)
#### Post date: [December 4, 2017, 7:23am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/5 "2017-12-04T07:23:35Z")
thanks magnus for the advise. yes i'll set a test env for this.
this one is working to get the current date.
```
ruby {
code => "
event.set('dateko', Time.now.strftime('%Y-%m-%d'))
"
}
```
this one is not for yesterday's date
```
ruby {
code => "
event.set('datemo', DateTime.yesterday.strftime('%Y-%m-%d'))
"
}
```
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 1, 2018, 7:23am UTC](https://discuss.elastic.co/t/compare-two-fields/110088/6 "2018-01-01T07:23:46Z")
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