I have a text file with the following content in it.

    $ cat hosts.yml
    [prod_env]
    foo.example.com
    bar.example.com
    [stage_env]
    foo_stage.example.com
    bar_stage.example.com
    [dev_env]
    foo_dev1.example.com
    dev2_bar.example.com

I would like to filter hosts listed under [prod_env] file in bash.
I tried with sed, awk and grep with my limited knowledge, but I am not sure how to filter them.

Example: I would like to print hosts under prod_env and dev_env. so the final output would be:

    foo.example.com 
    bar.example.com 
    foo_dev1.example.com 
    dev2_bar.example.com