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

[arnold]

Hi. Thanks for the note.

Steven Penny <address@hidden> wrote:

> Good:
>
>     $ awk 'BEGIN {print system("grep")}'
>     Usage: grep [OPTION]... PATTERN [FILE]...
>     Try 'grep --help' for more information.
>     2
>
> Bad:
>
>     $ awk --posix 'BEGIN {print system("grep")}'
>     Usage: grep [OPTION]... PATTERN [FILE]...
>     Try 'grep --help' for more information.
>     512
>
> Note that Mawk and Nawk produce the expected "2".

When gawk behaves differently with and without --posix, there is a reason.
Please see

        
https://www.gnu.org/software/gawk/manual/html_node/I_002fO-Functions.html#I_002fO-Functions

which describes the behavior of system() in detail. The relevant part:

        Traditionally, awk's system() function has simply returned the
        exit status value divided by 256. In the normal case this gives
        the exit status but in the case of death-by-signal it yields a
        fractional floating-point value. POSIX states that awk's system()
        should return the full 16-bit value.

        gawk steers a middle ground. The return values are summarized
        in Table 9.5.

See the cited URL for the table.

Thanks,

Arnold