The stdout filter plugin allows printing to the standard output the data flowed through the filter plugin, which can be very useful while debugging.
The plugin has no configuration parameters, is very simple to use.
$ fluent-bit -i cpu -F stdout -m '*' -o null
Fluent Bit v1.x.x
* Copyright (C) 2019-2021 The Fluent Bit Authors
* Copyright (C) 2015-2018 Treasure Data
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io
[2021/06/04 14:53:59] [ info] [engine] started (pid=3236719)
[2021/06/04 14:53:59] [ info] [storage] version=1.1.1, initializing...
[2021/06/04 14:53:59] [ info] [storage] in-memory
[2021/06/04 14:53:59] [ info] [storage] normal synchronization mode, checksum disabled, max_chunks_up=128
[2021/06/04 14:53:59] [ info] [sp] stream processor started
[0] cpu.0: [1622789640.379532062, {"cpu_p"=>9.000000, "user_p"=>6.500000, "system_p"=>2.500000, "cpu0.p_cpu"=>8.000000, "cpu0.p_user"=>6.000000, "cpu0.p_system"=>2.000000, "cpu1.p_cpu"=>9.000000, "cpu1.p_user"=>6.000000, "cpu1.p_system"=>3.000000}]
[0] cpu.0: [1622789641.379529426, {"cpu_p"=>22.500000, "user_p"=>18.000000, "system_p"=>4.500000, "cpu0.p_cpu"=>34.000000, "cpu0.p_user"=>30.000000, "cpu0.p_system"=>4.000000, "cpu1.p_cpu"=>11.000000, "cpu1.p_user"=>6.000000, "cpu1.p_system"=>5.000000}]
[0] cpu.0: [1622789642.379544020, {"cpu_p"=>26.500000, "user_p"=>16.000000, "system_p"=>10.500000, "cpu0.p_cpu"=>30.000000, "cpu0.p_user"=>24.000000, "cpu0.p_system"=>6.000000, "cpu1.p_cpu"=>22.000000, "cpu1.p_user"=>8.000000, "cpu1.p_system"=>14.000000}]
[0] cpu.0: [1622789643.379507371, {"cpu_p"=>39.500000, "user_p"=>34.500000, "system_p"=>5.000000, "cpu0.p_cpu"=>52.000000, "cpu0.p_user"=>48.000000, "cpu0.p_system"=>4.000000, "cpu1.p_cpu"=>28.000000, "cpu1.p_user"=>21.000000, "cpu1.p_system"=>7.000000}]
^C[2021/06/04 14:54:04] [engine] caught signal (SIGINT)
[2021/06/04 14:54:04] [ info] [input] pausing cpu.0
[2021/06/04 14:54:04] [ warn] [engine] service will stop in 5 seconds
[2021/06/04 14:54:08] [ info] [engine] service stopped
