Digital cameras are doing a nice job of putting in datetime and exposure information into the generated JPEG file. It's useful to be able to read that.
There is some good stuff out there: - a perl script called captivate, which in turn requires a program called epinfo.
Warning! A lot of bad programs out there mangle this metadata!! So, for example, you may do a trivial operation like rotating a portrait picture, and it might clobber your metadata.
One of the cool things that become possible when you have a large database of image files is that you can randomly show different images on your root window. There are many programs which do this, but I wanted a different featureset. Here are files of my effort -- documentation and program (in perl).
Back up to These are a few of my favourite toys (my devices page)