I was discussing a different scenario, "NFS mounts can get eternally stuck processes when they die because the other end of the file descriptor doesn't exist an

I was discussing a different scenario, "NFS mounts can get eternally stuck processes when they die because the other end of the file descriptor doesn't exist and there is nothing the kernel can reasonably do about it" — the kernel absolutely can do a reasonable thing and return from write(2) with whatever error code. And yes, Windows API's WriteFile does actually return less lpNumberOfBytesWritten than was passed in nNumberOfBytesToWrite, but only when writing to a non-blocking pipe; the disk writes are either fully written or fully failed. Sockets use their own special API that generally follows the write(2) semantics (although there are some hilarious corner cases with internal buffers: e.g., you can make a 1 GB write to a write-ready non-blocking socket and the internal buffer will grow to accomodate it, but further write requests will return EAGAIN).