I need a non-interactive way to tell xwd what X window to make an image of...
NOT by the traditional point-and-click method.
[Last modified: July 95]

Answer: Ken Sall (ksall@cen.com) wrote:

1. Get the window id of the toplevel shell widget using the "XtWindow"
function.
2. Invoke "xwd" from the program that has access to the window id, such as:

Window dumpId; /* returned from XtWindow */
sprintf (cmd_string, "xwd -frame -out tmp.xwd -id 0x%x", dumpId);
system (cmd_string);