Access Special Info in files, like photos, audio, video

I am trying to automate the sorting of files using shell scripting.

I want to file different things in different places based on things like:

- what camera they were taken from

- what resolution the picture is

- perhaps GPS location

- for mp3's maybe audio compression or codec

- for audio files, are the podcasts, from an iPhone, voice recorder.

For example I dump files into a directory and want a cron job to take

any .jpg files and figure out where they came from? Were they downloaded

from the Internet, saved from email, taken from a camera or phone, if so

what device.

I know there is data somewhere in these files, and that finder, preview

and other programs can find it and get at it, but is there a way to do it

on my own?

I have heard of resource forks but I really have no idea what they are or

how to access them. If I could figure that out, or even where the data

might be inside the file and I could pull it out with shell commands, but

where is any of this data documented?

Just a pointer for jpg's, mp3's. mov's, mp4's would be a great start.