This is the mail archive of the cygwin mailing list for the Cygwin project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

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
<> 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 [1] 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.

Sorry, no advice getting around this, but a thought about why it may have
been hard -- it can be a security hole.  Given Windows' complex access rights,
how would one determine which processes should reasonably have access to
another process's environment variables?  Maybe Windows decided to punt the
issue.  (I don't know anything about this at all - as I said, just a

A question: Are there any Windows tools that can do this?  If so, you might
be able to trace them to find what they do.

Regards -- Eliot Moss

Problem reports:
Unsubscribe info:

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]