#include <X11/Xlib.h>#include <X11/Xutil.h>#include <X11/Xos.h>#include <stdio.h>#include <string.h>int main ( int argc, char ** argv ){ Display * display; display = XOpenDisplay ( NULL ); if ( display==NULL ) printf("XOpenDisplay - error!\n"); else { printf("XOpenDisplay - OK!\n"); XCloseDisplay ( display ); } return 0;}makefile:CC=gccall: xopen.c $(CC) $? -Wall -lao -lX11 -o xopen