If the manpage on Mac OS does not mention the -n. it could be that /bin/echo would behave properly if you try that. However most (if not all?) shell implement echo as a builtin command. and especially bash which is the default shell on Mac OS iirc. So when you call "echo", you effectively call the bash builtin which features a ton of new flags for the echo command. As phillbush and OpenBSD put it, use printf when portability is an issue (echo is considered broken and deprecated in many places).