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

[Eric Blake]

On 8/16/20 10:47 AM, Todd A. Jacobs wrote:

> Description:
>          The echo builtin accepts options, but does not seem to handle
>          `--` correctly as the end of options.

The correct behavior for echo is described here:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
"The echo utility shall not recognize the "--" argument in the manner 
specified by Guideline 10 of XBD Utility Syntax Guidelines; "--" shall 
be recognized as a string operand."

> The expected behavior
>          would be for -- to be removed, and any following flag-like
>          substrings printed as-is.

Your expectations are wrong, they contradict what POSIX says.

> Repeat-By:
>          echo "-n"         # "" but expecting "-n"

POSIX says this one is implementation-defined; so whether -n is treated 
as an option or as a string to echo has to be documented by the 
implementation (bash documents treating it as an option).

>          echo -- -n foo    # -- -n foo

POSIX says this has to output '-- -n foo' and a newline. -n wasn't 
first, so you no longer have the implementation-defined behavior, but 
well-defined.

>          echo -- "-n foo"  # -- -n foo

Also well-defined.

I see nothing in your report about bash disobeying POSIX, but rather 
confusion on your part about what POSIX actually requires.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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