X11 capturing DISPLAY value

Jon TURNEY jon.turney@dronecode.org.uk
Mon Mar 11 13:33:00 GMT 2013

On 10/03/2013 22:17, wynfield@gmail.com wrote:
> I wanted to capture the X11 DISPLAY value that shows on the console when 'startx &' in invoked and successful.  I've tried:
>  startx 2>&1 | grep DISPLAY\= >/tmp/xwin.txt &
>  startx 2>&1 | grep DISPLAY >/tmp/xwin.txt &
> but neither worked.  I could check files in /tmp/.X11-unix/* for date, owner, etc, and hope that the newest one is the right one and extract the number from the name, however if another user started an X window in the meantime I'd get the wrong DISPLAY v
> alue.
> Is there a preferred standard way to get this value?

If you cannot explicitly specify a display number, I would say, use the
'-displayfd' X server option [1], for example:

xinit -- -displayfd 3 3>~/.display
export DISPLAY=:`cat ~/.display`

Unfortunately, while this works with xinit, it seems there are bugs not
noticed until now which prevents this from working correctly with startx
(startx ends up supplying both :display and -displayfd, which doesn't work
correctly, and the xauthority generated may reference the wrong display
number, leaving clients unable to connect)

[1] http://x.cygwin.com/docs/ug/using-terminal-server.html

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