Re: xargs: doesn't fail on missing terminator (which may have severe consequences)

On Mon, 2024-12-09 at 21:00 +0100, Bernhard Voelker wrote:
> The above test case can be simplified to the cases:
> 
>    $ printf 'hello' | xargs -0 printf "<%s>\n"
>    <hello>
> 
>    $ printf 'hello\0' | xargs -0 printf "<%s>\n"
>    <hello>
> 
>    $ printf 'hello\0world' | xargs -0 printf "<%s>\n"
>    <hello>
>    <world>
> 
>    $ printf 'hello\0world\0' | xargs -0 printf "<%s>\n"
>    <hello>
>    <world>

Sure, I merely tried to use an example which also shows how easy such a
truncated record could happen by merely signal at the wrong time.
In the above example one may easier confuse it with: "you send wrong
data, your own fault"


> 
> > This problem is even mentioned in the most recent 2024 edition of
> > POSIX:
> > https://pubs.opengroup.org/onlinepubs/9799919799/utilities/xargs.html
> > 
> > > FUTURE DIRECTIONS
> > > A future version of this standard may require that, when the -0
> > > option is specified, if the standard input is not empty and does
> > > not
> > > end with a null byte, xargs ignores the trailing non-null bytes.
> > 
> > I'll ask at the WG, whether it wouldn't be better to give an error
> > instead of ignoreing it.
> 
> IMO the above, current bahavior is not that terribly bad, but rather
> quite good and consistent.

Which one, the one that's indicated as a future direction, or the one
that actually allows (but I think recommends against) it for now and
which is also xargs current behaviour?

Cause the latter would IMO be terribly bad, just imagine you have
something like;

  find / -type f -name '*.backup' -print0  |  xargs -0 rm -f

If by accident, you now get only the `/` from the actual
`/foo/bar/baz.backup`, you'd remove everything.


> A question in this context may rather be how xargs(1) should handle
> empty, i.e.,
> Zero-length, entries: 'hello\0\0world'.

I'd say that these should be simply empty arguments? Like in
  some_command 'hello' '' 'world'
except that I'd not consider the world, as it's not properly
terminated.


Cheers,
Chris.