Linux: QStandardPaths: XDG_RUNTIME_DIR points to non-existing path

JonB

I am getting an error/warning

QStandardPaths: XDG_RUNTIME_DIR points to non-existing path

I would like some Linux expert to spare me a few minutes to explain what this is all about, please! (It will need a Linux bod.)

My question might look scary, but it shouldn't be really. I just need an explanation of what's going on here.

I had a working system without this problem in my old Ubuntu 17.04 installation. I have moved to a fresh Ubuntu 18.04, with a change in the way a component has been installed, and this has reared its head.

I use Qt (5.9.5, as per apt-get for the distro). I use Python/PyQt. I use PyCharm for the IDE/debugger, and that is where the warning occurs. However I don't expect you to have to know about those details, and I would presume the issue/question would occur in principle if I were using C++/gdb. Please read on...

PyCharm is not installable via apt-get (sigh). You have to do it manually. Previously I did it by un-tarring etc., and put the result into the system area. It worked, but there were issues about taking upgrades. This time, hoping to avoid update issues, I followed a post on the net advising to use Linux

sudo snap install pycharm-community --classic

When I launch my app from within PyCharm debugger I now get 2 occurrences of:

QStandardPaths: XDG_RUNTIME_DIR points to non-existing path '/run/user/1000/snap.pycharm-community', please create it with 0700 permissions.

/run/user/1000 does exist, but not the sub-directory. I created that appropriately yesterday, and the error went away. However, today it is back. I believe the sub-directory does not persist/gets removed across either login session or reboot? It is not convenient to have to re-create it all the time.

My shell has environment variable

XDG_RUNTIME_DIR=/run/user/1000

and that works without complaint if I run my app from there. I can force the same error outside of PyCharm by running

env XDG_RUNTIME_DIR=/run/user/1000/rubbish my-Qt-application

So my questions, at least for my edification, are:

What exactly is this "XDG" stuff all about (because I'm interested)?
Why does QStandardPaths care about it?
It looks like PyCharm, as a result of my installing it via "snap" (which I know nothing about), is choosing to export the variable changed to require a snap.pycharm-community sub-directory, which does not exist. Is that a "normal" thing to do?
Is it right that creating the sub-directory seems to get deleted at that location?

Before anyone answers "go ask PyCharm", I have previous experience that questions there simply don't get answered :( So although it may their issue, I'd appreciate any insights here from my kind expert-friends (e.g. I might be looking at you, friend @kshegunov) as to what is going on and how it affects Qt, please?

Otherwise I'm wondering about uninstalling the whole of "snap PyCharm" and starting again down some manual route....

SGaist

Hi,

Since you're on Ubuntu, this thread on askubuntu should bring some lights.
Because it's a standard
That's a question for the snap people
Sorry, don't know, see number 3

JonB

@SGaist
Thank you for answering. @Christian-Ehrlicher also helped me out on this.

I now understand this variable names a per-user temporary directory. With a strange name of XDG_RUNTIME_DIR it did not occur to me that's what it might be! I also have not come across path /run/user/... before. It wasn't like that in Unix 25 years ago!

Christian did show me what it is Qt uses the for --- some kind of "writeable location" call --- by I cannot locate it. Can you remind me what it is Qt uses this for?

So the problem is: I start out with an XDG_RUNTIME_DIR set to /run/user/1000 and that does exist, all is well. But when I launch my app inside PyCharm it must be altering that variable to /run/user/1000/snap.pycharm-community, which does not exist. Presumably, either it should not do that, or it should be creating that directory first.

I also now understand that since it is supposed to be a temporary directory, that's must be why /run/user/1000 gets cleared out across each login/reboot, so if I create it it later disappears.

This did not happen prior to upgrade/new install. I think I might uninstall PyCharm and revert to my old, manual install process (not using snap), and hope this behaviour disappears....

SGaist

It is used by QStandardPaths to provide a writable location for different purpose that your application may need.