I think it's rather short-sighted to think of a shell pipeline as unidirectional. Imagine if you want to be able to provide random seeking capability to your in

I think it's rather short-sighted to think of a shell pipeline as unidirectional. Imagine if you want to be able to provide random seeking capability to your input source but the seek destinations determined by the output consumer? That's rather difficult to do with a unidirectional pipeline.