EDIT: Okay, this is at -1, maybe I shouldn't be slightly obtuse. These questions are, in my mind, two sides of the same coin. The OS expects null terminated strings, not for some inherent reason, but because C and UNIX grew up together. There's no inherent reason you can't have an OS that does not use sentinels to demarcate strings.

I'm actually a little curious how what these low-level APIs look like and how "modern" languages handle efficiently converting to null-terminated strings. Do they just copy everything while C/C++/etc would pass a straight reference? Also, what do the underlying syscall APIs look like?

And yeah, in Rust we have a separate CString type that's null terminated, so you may need a copy to move between the two worlds. It just depends, if you're only reading, for example, then you can create a pointer + len where the length doesn't include the 0, and that's effectively zero cost.

You got me curious about my days as a kid putting "pascal" in front of Mac System 7 stuff; I believe that it only accepted Pascal strings. I also vaguely remember people doing funny stuff like null terminating pascal strings anyway and then putting the length before the actual pointer so that you get both in one...