I've seen people using *.cfg (Python Buildout), *.xml (Gnome), *.json (Chrome extension), *.yaml (Google App Engine), *.ini and even *.py for app configuration files (like Django).
My question is: why there are so many different configuration file formats? I can see an advantage from a xml vs json approach (much less verbose) or a Python one (sometimes you have a Python app and don't want to use a specific module just to parse a config file), but what about the other approaches?
I know there are even more formats than those configuration files I exemplified. What are really their advantages in comparison to each other? Historical reasons? Compatibility with different systems?
If you would start an application to read some kind of configuration files (with a plugin ecosystem), which one would you use?
Which ones that I gave as example are the oldest ones? Do you know it's history?
Simple configuration languages, such as JSON, work for many applications, but when you need proper validation, schema, and namespace support, XML is often best.
Configuration files ("config files" for short) are important to modern computing. They allow you to customize how you interact with an application or how an application interacts with the rest of your system.
YAML is a digestible data serialization language often used to create configuration files with any programming language. Designed for human interaction, YAML is a strict superset of JSON, another data serialization language. But because it's a strict superset, it can do everything that JSON can and more.
It's mostly personal preference, purpose, and available libraries. Personally I think xml is way too verbose for config files, but it is popular and has great libraries.
.cfg, .ini are legacy formats that work well and many languages have an included library that reads them. I've used it in Java, Python, C++ without issues. It doesn't really work as a data interchange format and if I am passing data I will probably use the same format for config and data interchange.
yaml, and json are between xml and cfg/ini. You can define many data structures in both, or it can be a simple key-value like with cfg. Both of these formats have great libraries in python and I'm assuming many other languages have libraries as well. I believe json is subset of yaml.
I've never used a python file as config, but it does seem to work well for django. It does allow you to have some code in the config which might be useful.
Last time I was choosing a format I chose yaml. It's simple but has some nice features, and the python library was easy to install and really good. Json was a close second and since the yaml library parsed json I chose yaml over it.
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