hey lovedebug,
Even i faced same problem on windows using command line
command bin\logstash -f a.conf
Error:
Sending Logstash's logs to C:/Users/sampth/Downloads/logstash-6.1.1/logstash-6.1.1/logs which is now configured via log4j2.properties
[2018-01-06T21:14:04,772][INFO ][logstash.modules.scaffold] Initializing module {:module_name=>"fb_apache", :directory=>"C:/Users/sampth/Downloads/logstash-6.1.1/logstash-6.1.1/modules/fb_apache/configuration"}
[2018-01-06T21:14:04,772][INFO ][logstash.modules.scaffold] Initializing module {:module_name=>"netflow", :directory=>"C:/Users/sampth/Downloads/logstash-6.1.1/logstash-6.1.1/modules/netflow/configuration"}
[2018-01-06T21:14:04,944][WARN ][logstash.config.source.multilocal] Ignoring the 'pipelines.yml' file because modules or command line options are specified
[2018-01-06T21:14:05,366][INFO ][logstash.runner ] Starting Logstash {"logstash.version"=>"6.1.1"}
[2018-01-06T21:14:05,445][INFO ][logstash.config.source.local.configpathloader] No config files found in path {:path=>"C:/Users/sampth/Downloads/logstash-6.1.1/logstash-6.1.1/a.conf"}
[ERROR] 2018-01-06 21:14:05.453 [Ruby-0-Thread-1: C:\Users\sampth\Downloads\logstash-6.1.1\logstash-6.1.1\lib\bootstrap\environment.rb:6] sourceloader - No configuration found in the configured sources.
[2018-01-06T21:14:05,613][INFO ][logstash.agent ] Successfully started Logstash API endpoint {:port=>9600}
After hard struggle i found that my config format was in .txt format
i again had to save it as a.config file using editor(making sure it is not .txt file)
hope it solves your problem.