Re: [1003.1(2013)/Issue7+TC1 0001016]: race condition with set -C

[Martijn Dekker]

Op 07-11-16 om 03:55 schreef Shware Systems:
> To last question, yes, but the effects are supposed to be documented so
> generic guard code that may invoke platform specific pre-ln attempt
> handling can be written. This is a compromise to disqualifying a system
> that defines additional file types from being considered conforming at
> all. In a script this might look like:
> if [ -e /app/$platform/linkhandler ] ;
> then { . .../linkhandler }
> else { do ln directly }; fi

Thanks for the reply. Where can I find more info about this? Is there a
standardised /app directory structure? I don't find it on any actual
system I've access to.

> To some extent it's also the operator's responsibility to sandbox use of
> non-standard file types outside directories the standard says portable
> applications need access to, such as $TMP, to avoid issues.

That makes sense. Many things would break if /tmp does not operate portably.

> A platform
> aware application might create such a file in a $TMP/appsubdir directory
> but shouldn't link it into /tmp after, iow, but to an ~/app/files type
> directory instead. That is more a training issue to me, not something
> the standard can reasonably address or make a requirement.

Unfortunately, by far the most common use case of 'mktemp' is to create
a temporary file in /tmp, so my cross-platform shell implementation of
it will have to be able to do that.

For the time being, unless anyone has concrete evidence or convincing
arguments to the contrary, I will assume that any issues with 'ln'
atomicity into /tmp are theoretical.

- M.