Logstash --configtest & stdout

I have an annoying little problem on a logstash 2.3.4 installed (from the repo) on a Linux Mint development box
May be this problem is more linux oriented.
I would like to catch the result of a configtest command

In a shell, the command " /opt/logstash/bin/logstash --configtest" shows the line "Configuration OK"
But this output doesn't seem to be bound to the process standard output.

/opt/logstash/bin/logstash --configtest > test
==> test is an empty file

In contrast, a --version command is OK for me
/opt/logstash/bin/logstash --configtest > test
==> test contains "logstash 2.3.4"

I'm looking for a workaround...


Presumably the output is sent to stderr and not to stdout.

I did checked this too (/opt/logstash/bin/logstash --configtest 1> test 2> test)

Also tried to redirect to log (/opt/logstash/bin/logstash --configtest --log test)

.. Actually diving in Ruby code That I don't know at all..

As a workaround, I changed one line in agent.rb

# currently the best strategy to validate the configuration
# is creating a pipeline instance and checking for exceptions
#@logger.terminal "Configuration OK"
puts "Configuration OK"
return 0