[pdftex] Access value of output-directory

[Karl Berry]

    am I right that there is no way to access the value of the
    '-output-directory' command line option from within pdfTeX?

As far as I can recall (and discern from a quick glance at the sources),
that is correct. I'm sure someone will correct me if I'm wrong.

    If true, I think it would be very convenient for package authors
    if you could provide a new primitive to do so.

It could be done. But what do you want to do with the value?

    I understand that one can access the argument vector from within
    LuaTeX, but I think a lot of authors would rather not make their
    packages LuaTeX-only (at least for now).

Fully agreed. Although it's clear that "a lot of authors" don't need
the output-directory value, since it has never been available at the TeX
level -- yours is the first request I remember ever seeing, anywhere.

best,
karl