[Users] firefox opens new copy of claws

[Michael Schwendt]

On Mon, 6 Jan 2020 13:21:17 +0000, Dave Howorth wrote:

> > If you set $TMPDIR for your user, does that make a difference?
>
> Sorry I don't understand. I don't know what those tmpdirs are used for
> or their relevance to my problem, nor understand how to fix it. Sorry
> to be so ignorant.

Find some background in this old ticket about Fedora/Red Hat:
https://bugzilla.redhat.com/show_bug.cgi?id=956380#c5

In the tmp directory, Claws Mail stores runtime files that are used to
detect an already running instance.

Basically, Claws Mail defaults to using /tmp based on what g_get_tmp_dir()
returns, if no environment variables have been customized. And Firefox
defaults to something else *and* may export that to the runtime environment
when launching Claws Mail, so where it would use /tmp by default, suddenly
it would use the different dir exported by Firefox. Boom!