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Re: Retrieving per-process environment block?
On 11/29/2016 8:26 AM, Erik Bray wrote:
> On Thu, Nov 17, 2016 at 3:00 PM, Corinna Vinschen
> <firstname.lastname@example.org> wrote:
>> On Nov 17 14:30, Erik Bray wrote:
>>> Hi all,
>>> For a quick bit of background, I'm working on porting the highly
>>> useful psutil  Python library to Cygwin. This has proved an
>>> interesting exercise, as much of the functionality of psutil works on
>>> Cygwin through existing POSIX interfaces, and a handful of
>>> Linux-specific interfaces as well. But there are some bits that
>>> simply don't map at all.
>>> The one I'm struggling with right now is retrieving Cygwin environment
>>> variables for a process (under inspection--i.e. not listing a
>>> process's environment from within that process which is obviously
>>> I've looked at every route I could conceive of but as far as I can
>>> tell this is currently impossible. That's fine for now--I simply
>>> disable that functionality in psutil. But it is unfortunate, though,
>>> since the information is there.
>>> There are a couple avenues I could see to this. The most "obvious"
>>> (to me) being to implement /proc/<pid>/environ.
>>> I would be willing to provide a patch for this if it would be
>>> accepted. Is there some particular non-obvious hurdle to this that it
>>> hasn't been implemented? Obviously there are security
>>> implications--the /proc/<pid>/environ should only be readable to the
>>> process's owner, but that is already within Cygwin's capabilities, and
>>> works for other /proc files.
>> Patch welcome. Implementing this should be fairly straightforward.
>> The only hurdle is winsup/CONTRIBUTORS ;)
> Thanks--I went to go work on this finally but it turns out not to be
> straightforward after all, as the process's environment is not shared
> in any way between processes.
> I could do this, if each process kept a copy of its environment block
> in shared memory, which would in turn have to be updated every time
> the process's environment is updated. But I don't know what the
> impact of that would be performance-wise.
> Any advice?
Sounds like a job for a thread that wakes every X time units to check
the contents of the environment. Or is there a notification API that
could be used to wake the thread? I know there is a disk change
notification API for this; maybe one for environment changes as well.
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