fork/exec & close file descriptors

[Alain Ketterlin]

Marko Rauhamaa <marko at pacujo.net> writes:

> Alain Ketterlin <alain at universite-de-strasbourg.fr.invalid>:
>
>> Marko Rauhamaa <marko at pacujo.net> writes:
>>> First, if close() fails, what's a poor program to do?
>>
>> Warn the user? Not assume everything went well? It all depends on the
>> application, and what the file descriptor represents.
>
> The problem here is in the system call contract, which is broken.
> There's no fix. The man page admonition is just hand-waving without
> constructive advice.
>
>>> Try again?
>> Could be a good idea on NFS or other kind of mounts.
>
> Maybe close() will fail for ever.

Your program has to deal with this, something is going wrong, it can't
just close and go on.

>> I can't imagine why one would like to mass-close an arbitrary set of
>> file descriptors,
>
> That's standard practice before execking a file. [...]

>> and I think APIs like os.closerange() are toxic and an appeal to
>> sloppy programming.
>
> And you recommend what instead?

Keeping them around and closing the ones you own, plus doing whatever is
necessary to have libraires (loggers, database connectors, etc.) finish
properly. And not taking the risk of messing with descriptors your
program is not responsible of.

-- Alain.