Unpacking data files

Hola,

Came across these boards as I was interested in learning how to extract data from from the number of random formats that games generally use. I don't really want to use a ready made tool, but more want to learn about the techniques that you can use to actually work out the crazy way how you can split files out and extract what you are actually looking for. For example images and game item information (stats,requirements for example).

I am pretty happy to use shell scripts (and mostly live in linux/mac environments) but I have no experience when it comes to this. For example I am interested in extracting item information, descriptions and images from a particular game (in this case, ragnarok online 2) and after some googling, it had brought me to here and linked to a couple of tools created by this community.

However outside of one post i found here talking about the structure, but i cannot post links xD, I wasn't really able to find much information as to how I can even start going about this. So I was hoping to get some tips and pointers so I can come up with a few scripts that will help me extract and re-format the said information.

Thanks for the help!