Thanks @harshbajaj16
indeed, I'm using Elasticsearch 6.0.1, Filebeat 6.0.1 and Kibana 6.0.1 under java8.
Eventually I managed to solve this issue.
I didn't pay attention that my filebeat.yml path wasn't the good one.
thanks for your help.
filebeat.prospectors:
# Each - is a prospector. Most options can be set at the prospector level, so
# you can use different prospectors for various configurations.
# Below are the prospector specific configurations.
- type: log
# Change to true to enable this prospector configuration.
# enabled: false
enabled: true
# Paths that should be crawled and fetched. Glob based paths.
paths:
# - /var/log/*.log
#- c:\programdata\elasticsearch\logs\*
- C:\ProgramData\ngnix\logs\*