Matthew Seaman m.seaman at
Tue Oct 14 02:22:35 PDT 2003

On Tue, Oct 14, 2003 at 12:03:47AM -0400, Gerald S Stoller wrote:
> FreeBSD  4.3-RELEASE FreeBSD 4.3-RELEASE #0: Sat Apr 21 10:54:49 GMT 2001
>     jkh at  i386
>         I run  XFree86  on my system.  Each process has an environment
> variable named  WINDOWID .  What purpose does this variable  serve?  How
> is it used?  What can I do with it ((redirect output to another window,
> no! for that I can use  /dev/tty )?  I noticed (by converting several
> values to hex) that the form of this variable  is
>   2 * y * 16^5 + 14 , and I never saw  y > 22 ; this is a result of
> looking at around a dozen values.

Actually, that's set for all of the child processes of any xterm(1)
windows you may use.  It seems to be an xterm(1) specific thing to set
in the environment, but then I haven't actually checked any of the
xterm-alike programs.  As far as I know, it's not used for anything
much from the shell.

The WINDOWID value itself just reports the Window id value known to
the X server -- all X windows on the server will have a unique ID
number which is used within the server to make sure that X events and
window updates and so forth get directed to the right place.  Use
xwininfo(1) to display that, and other, data about any windows on your
display.  xwininfo(1) returns the window id value in hex, and it does
have the same sort of pattern for all windows as you mention.  It
looks like some sort of bitmap to me, probably to tell the X server
what the capabilities of the window are, but I can't find the
appropriate man page that describes that.  Try using xwininfo(1)
against the root window, icons and so forth.



Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP:         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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