xlib events

#include <X11/Xlib.h>  
#include <cassert>  
#include <unistd.h>  
#include <cstdlib>  
#include <cstdio>  
#include <wait.h>  
#include <iostream>  
#include <fcntl.h>  
#include <string>  
  
using namespace std;  
  
int main( int argc, char ** argv ) {  
  
   string app = "gedit";  
  
   int pid = fork();  
   if ( pid == 0 ) {  
      execlp( app.c_str(), app.c_str(), NULL );  
      exit( 0 );  
   }   
  
  
   int status;  
   waitpid( pid, &status, WNOHANG );  
  
   sleep(2);  
  
   string cmd =   
      string() + "xwininfo -tree -root -int | grep " + app.c_str() +   
      " | awk '{ print $1 }' | tail -n 1";   
  
   FILE * wininfo = popen( cmd.c_str(), "r" );  
  
   char wid_str[ 80 ];  
   fread( (void *) wid_str, sizeof( char ), sizeof( wid_str ), wininfo );  
     
   pclose( wininfo );  
  
   Window w = (Window) atol( wid_str );  
  
   Display * dpy = XOpenDisplay( NULL );   
  
   XSelectInput( dpy, w, KeyPressMask | KeyReleaseMask );  
  
   while (1) {  
      XEvent event;  
      XNextEvent( dpy, &event );  
      cout << "!" << endl; 
   }  
  
   XCloseDisplay( dpy ); 
 
   return 0;  
}  

fread( (void *) wid_str, sizeof( char ), sizeof( wid_str ), wininfo );  

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