2019-08-14 09:28:22 -0700, Kaz Kylheku (Coreutils): [...] > According to POSIX, echo doesn't take options. It is specified > that "Implementations shall not support any options." > (We have options, though, so things are complicated.) [...]
The POSIX specification of "echo" is going to change in a future version. See: http://austingroupbugs.net/view.php?id=1222 and http://austingroupbugs.net/view.php?id=1222#c4375 for the accepted new text. In short, except when they implement the XSI option (which they need to to claim the UNIX trademark) implementations are going to be allowed to support a "-e", "-n" or "-E" option (but still not "--"/"-" to mark the end of option) and their behaviour will still be unspecified if any argument contains a backslash character (in practice, most implementations also fail if those arguments contain a multibyte character whose encoding contains byte 0x5c, which happens to be the ASCII encoding of backslash) Implementations that support an end of option marker include the "echo" builtin of zsh ("-", formerly "--"), fish ("--"), Byron Rakitzis clone of "rc" for Unix ("--") and its derivatives (es, akanga). With GNU "echo" (and GNU "env"), you can output "-n" or arbitrary $data with: env -u POSIXLY_CORRECT echo -En "$data " -- Stephane
