[gnulinux]

They might be programmatically generated, for example.

There are countless sources one can get a string from. Surely you don't think filesystems are the only source of strings?

[mixmastamyk]

Input is very rarely auto-generated, though output is.

Surely you haven't misread my comments above to such an extent? Perhaps not familiar with sockets.

[gnulinux]

No, I didn't misread, input can be self-generated of course. If you're writing a system that's designed like UserInput -> [BlackBox] -> Output, clearly user input won't be auto-generated. But if you factor [BlackBox] into a system like A -> B -> C, A -> D -> C, C -> Output, then each of those arrows will represent an input into the next system that was generated by something our devs wrote. This could be bunch of jsonlines (related to this thread) interpreted as string, a database, some in-memory structure, whatever.