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Subject: Re: [boost] [filesystem] temp_dir_path()
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-10-12 20:49:28

John B. Turpish wrote:
> On Mon, Oct 11, 2010 at 9:19 AM, Jeff Flinn
> <TriumphSprint2000_at_[hidden]> wrote:
> > Stewart, Robert wrote:
> >> Jeff Flinn wrote:
> >>>
> >>> calls TMPDIR the
> >>> "canonical Unix environment variable" and refers to the
> >>> following for that justification:
> >>>
> >>> Is the above reference sufficient to only rely on TMPDIR?
> >>
> >> I don't think so, but I'm inclined to say don't look for
> >> /tmp. That is, rely on the environment as the sole means
> >> to find the correct directory and if that is deficient,
> >> declare an error.
> >
> > I agree it's not a good idea to look for a fixed path. I
> > don't have broad enough UNIX systems experience to make the
> > call on whether to look for additional environment
> > variables. If TMPDIR *is* the POSIX standard should that be
> > all that we support?
> I'm not going to pretend to be an expert, but I just ran a
> simple test. Of those environment variables the only one I had
> set was TMPDIR (I did not set up my envs and was surprised,
> actually). I compiled and ran a program that did nothing more
> than print the return of tmpnam(NULL) to std::cout. It
> resulted in a file that was in a different directory than
> ${TMPDIR} (and not /tmp either). env | grep
> '' provided me with nothing. So I do not
> know where it got the directory for tmpnam(), but not from any
> env var.

According to <>, one should not
use tmpname(3) but should instead call mkstemp(3) or tmpfile(3).
The former makes a unique filename from a supplied template, so
it is the caller's responsibility to select the directory. The
latter creates a file which is deleted automatically when closed
or when the process terminates. Neither mentions e-vars as
influencing their behavior.

> Is it wrong for me to think tmpnam() would name to something in my
> temporary directory?

I wouldn't say it was wrong, but it was clearly misguided.

According to <>, mktemp(1)
references TMPDIR and falls back on /tmp unless "-p directory"
was set on the command line.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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