YAML to JSON one-liner

yaml2json

python3 -c 'import sys, yaml, json; y=yaml.safe_load(sys.stdin.read()); print(json.dumps(y))'

It will be faster if you use CLoader:
python3 -c 'import json, sys, yaml;from yaml import CSafeLoader as sl; y=yaml.load(sys.stdin.read(), Loader=sl) ; json.dump(y, sys.stdout)' && echo

@ptdel, I would look at the comments of the answer on StackOverflow. PyYAML development abruptly halted again and their release at the time of the comment broke many projects. While development seems to have resumed again, it appears that it comes in random bursts which is not always the best thing as a developer that is looking to have a pull request or other bugs resolved.

it appears that it comes in random bursts

I mean, that is pretty standard for many projects.

python3 -c 'import sys, yaml, json; json.dump(yaml.safe_load(sys.stdin), sys.stdout, indent=4)'

I usually want the pretty-print functionality.

If you only want pretty-print, and don't need JSON...

python3 -c 'import sys, yaml; yaml.dump(yaml.safe_load(sys.stdin), sys.stdout)'