Re: [bug-gawk] POSIX mode "system" returing invalid exit status

[arnold]

Hi.

Steven Penny <address@hidden> wrote:

> On Fri, Mar 23, 2018 at 2:07 AM, arnold wrote:
> > When gawk behaves differently with and without --posix, there is a reason.
>
> Thanks for the reply. I checked here [1] and dont see any mention of "16-bit
> value". No mention here [2] either.

>From http://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html:

system(expression)
        Execute the command given by expression in a manner equivalent to
        the system() function defined in the System Interfaces volume
        of POSIX.1-2017 and return the exit status of the command.
                                       ^^^^^^^^^^^

>From http://pubs.opengroup.org/onlinepubs/9699919799/functions/system.html:

        If command is not a null pointer, system() shall return the
        termination status of the command language interpreter in the
        format specified by waitpid().

This format is further described by 
http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_13;
it includes more than the just the low 8 bits of the exit status.

POSIX doesn't describe the layout of the exit status, instead specifying
macros in http://pubs.opengroup.org/onlinepubs/9699919799/functions/waitpid.html
for accessing the information.

The upshot is that gawk's --posix behavior is correct, if not terribly
useful.

Thanks,

Arnold