Get an X window ID

Eamon Walsh ewalsh at
Thu May 17 14:55:42 PDT 2007

Alan Coopersmith wrote:
> Daniel Stone wrote:
>> On Thu, May 17, 2007 at 11:00:33AM -0500, Pat Kane wrote:
>>> Are you allowed to change Xlib and the X server?
>>> If so then this hack might help.
>>> A while ago I needed to know, from inside the X server,
>>> the PID of a process that created an X connection.
>>> I used spare pad bytes in the  xConnClientPrefix initial
>>> connection setup message to pass the PID from the client
>>> to the X server.  Note that clients might not be on the
>>> same machine so you also need the hostname of the client.
>> NetWM already allows you to use properties to encode the pid and
>> hostname of clients as window properties.
> Should we have Xlib or xcb automatically set these so that
> we don't have to wait for every application and toolkit to
> be modified to do so?

As long as it's clear that they can be misrepresented by the client.

The server could check the values with getpeerucred or whatever.  But 
that's not always possible.

Eamon Walsh <ewalsh at>
National Security Agency

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