I am wondering what is the difference between eval & fieldalias commands?
For example:
EVAL-app = if(isnull(service),app,service)
FIELDALIAS-log = service AS app
In the first case, if service is null, app stay as is.
In the second case, if service is null, app is null.
Can someone explain it please?
Thanks
@shayhibah
Search-time operation sequence will help you to understand this. 🙂
http://docs.splunk.com/Documentation/Splunk/7.2.0/Knowledge/Searchtimeoperationssequence
Thanks
I read this page and it gave me some more information but I still cannot understand why the output of FILEDALIAS is null in some cases.
@shayhibah please see the answer I placed on your other answers ask found here:
Hope this helps give some clarity to you for the FIELDALIAS function and its limitations!
@shayhibah
1)
EVAL-app = if(isnull(service),app,service)
In this case, we are deciding app
field on the basis of the service
. If service
is not available then app
will be the same value available in the event. which can be null (if app
not found in the event) or not null (if app
found in the event). So if service
field is available then service
will be assigned to the app
field. if service
field is not available then app
will be assigned to app
(if the event has app
field ). if app
field is not available then app
will be null.
2
FIELDALIAS-log = service AS app
In this case, we are deciding app
field on the basis of the service
field regardless of field available or not. So if service
field is available then service
will be assigned to the app
. if service
field is not available then app
will be null.