For my sins, I have a large folder full of .iff files, which I wanted to convert into a useable format.

GIMP has a plugin which can read .iff files, but you’ll need to build it yourself. Seems like a lot of effort for some pictures.

Thankfully ilbtoppm is available for most Linux distros and can convert to .ppm, which is readable by most image editors.

The command line for ilbtoppm is:

ilbtoppm somefile.iff >outputfilename.ppm

This is a bit clunky and a pain to run a hundred times for different filenames, so I knocked up a quick one-liner to convert all .iff files in a folder to .ppm

for f in *.iff; do ilbmtoppm "$f" >"${f%.*}.ppm"; done

As with most things, I’ve mainly written this for my benefit so I can refer to it in a few months/years when I forget what the hell I did.