[moring]

What would be the expected reaction if either puts or fflush returns an error code? You might think, write a message on stderr (which may be different from stdout), but what if stderr is also redirected to a full device? How would you react to the error code returned from that?

To me this is an indication that you need to know the context in which the program gets run, and its purpose in that context. Or you'd have to specify every edge case, but I've never seen that really work in practice.

[throwawaylinux]

> What would be the expected reaction if either puts or fflush returns an error code? You might think, write a message on stderr (which may be different from stdout), but what if stderr is also redirected to a full device? How would you react to the error code returned from that?

I don't think you would react any differently on stderr failure unless you had a more complex system with alternate ways to report such things configured.

Just ignore it and continue to report the major error (stdout) in your exit status.