Re: Unfortunate error message for invalid executable

[Martin D Kealey]

On Sun, 29 May 2022, 06:56 AA via Bug reports for the GNU Bourne Again
SHell, <bug-bash@gnu.org> wrote:

> Maybe the concern is that any additional calls (such as checking for path
> existence) may have unintended consequences [but that] seems unlikely.
>
> Therefore, IMHO it is very hard to argue with the fact that the file
> passed to the kernel does in fact exist


Actually it's quite easy to argue with that: a race condition between when
execve fails and when we subsequently check whether the file exists means
we could be hoodwinked into reporting the wrong error message in both
directions.

Either use fexecve (where it exists) to be CERTAIN that the file exists
before invoking it, or simply adjust the wording of the error message to
make the ambiguity clear.

Then again, "file (or its interpreter) does not exist" would cover both
cases without needing to check separately whether the file exists.

-Martin