cu_errx
cu_errx(1, "cgetset failed");
cu_errx(1, "unknown host %s", host);
cu_errx(1, "can't open remote file");
cu_errx(1, "loop in remote file");
cu_errx(1, "unknown error in remote file");
cu_errx(1, "speed out of range");
void cu_errx(int, const char *, ...)