bug#21416: "--" syntax for ignoring flags doesn't seem to work right with GNU /bin/echo

[Eric Blake]

tag 21416 notabug
thanks

On 09/04/2015 12:57 PM, Robert "Finny" Merrill wrote:
> ~/workspaces/diags-dev/s1 @bs360.sjc> /bin/echo --help
> Usage: /bin/echo [SHORT-OPTION]... [STRING]...
>   or:  /bin/echo LONG-OPTION
> Echo the STRING(s) to standard output.
> *snip*

This is a GNU extension; it is not POSIX compliant, but can easily be
overridden, as shown below.

> ~/workspaces/diags-dev/s1 @bs360.sjc> /bin/echo -- --help
> -- --help

Thanks for the report. However, this is working as required by POSIX:

http://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."

    "Implementations shall not support any options."

> 
> There doesn't seem to be a way to get /bin/echo to output the string "--help"

Ah, but there is:

$ POSIXLY_CORRECT=1 /bin/echo --help
--help

Also, POSIX says that 'echo' is outdated (not only because it violates
the standard syntax rules, but also because it has non-portable handling
of \), and that you should strongly consider using printf, in which
case, you would do:

$ printf -- %s\\n --help
--help

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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