/* You could either run this or you could do

     xprop -root CUT_BUFFER0 | sed -e 's/^[^"]*"//' -e 's/"$//'
*/

#include <X11/X.h>
#include <X11/Xlib.h>
#include <stdio.h>

main()
{
  int nbytes;
  Display *d = XOpenDisplay(NULL);

  fputs(XFetchBytes(d, &nbytes), stdout);
}