Operating system feature wish: userspace programmable files

I frequently find myself wishing for the ability to really treat the filesystem as an API. Imagine a file that:

I am aware the FUSE and plan9 exist, however, I’m imagining something easier. Imagine if a file could run a shell script, interpreted program, or compiled binary on read/write! It would be so powerful.

Micah R Ledbetter @micahrl