Re: echo builtin doesn't handle end-of-options flag

[Eric Blake]

On 8/16/20 11:20 AM, Eli Schwartz wrote:

> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
>
> echo does not accept options, and is not permitted to accept options
> including "--".
>
> bash does accept -n, -e, -E in violation of POSIX, unless shopt -s shopt
> -s xpg_echo is set, but it doesn't implement -- and I don't really see a
> justification to do so.

Not quite: https://www.austingroupbugs.net/view.php?id=1222 says that 
accepting -e and -E will become acceptable in the next revision of POSIX 
(accepting -n was already acceptable on non-XSI systems).

> Either enable xpg_echo or use printf.

POSIX recommends using printf. My personal recommendation is to avoid 
xpg_echo except when trying to break things - there are a number of what 
claim to be bash scripts that are not aware of the effects of xpg_echo 
and which operate incorrectly when you actually set it; whereas using 
printf is reliably portable.

--
Eric Blake, Principal Software Engineer
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