XOpenDisplay 3X11 __xorgversion__ XLIB FUNCTIONS XOpenDisplay XCloseDisplay connect or disconnect to X server Display *XOpenDisplay ( char *display_name ); int XCloseDisplay (Display *display ); display Specifies the connection to the X server. display_name Specifies the hardware display name, which determines the display and communications domain to be used. On a POSIX-conformant system, if the display_name is NULL, it defaults to the value of the DISPLAY environment variable. The  XOpenDisplay  function returns a  Display  structure that serves as the connection to the X server and that contains all the information about that X server.  XOpenDisplay  connects your application to the X server through TCP or DECnet communications protocols, or through some local inter-process communication protocol. If the hostname is a host machine name and a single colon (:) separates the hostname and display number,  XOpenDisplay  connects using TCP streams. If the hostname is not specified, Xlib uses whatever it believes is the fastest transport. If the hostname is a host machine name and a double colon (::) separates the hostname and display number,  XOpenDisplay  connects using DECnet. A single X server can support any or all of these transport mechanisms simultaneously. A particular Xlib implementation can support many more of these transport mechanisms. If successful,  XOpenDisplay  returns a pointer to a  Display  structure, which is defined in <X11/Xlib.h>. If  XOpenDisplay  does not succeed, it returns NULL. After a successful call to  XOpenDisplay , all of the screens in the display can be used by the client. The screen number specified in the display_name argument is returned by the  DefaultScreen  macro (or the  XDefaultScreen  function). You can access elements of the  Display  and  Screen  structures only by using the information macros or functions. For information about using macros and functions to obtain information from the  Display  structure, see section 2.2.1. The  XCloseDisplay  function closes the connection to the X server for the display specified in the  Display  structure and destroys all windows, resource IDs ( Window ,  Font ,  Pixmap ,  Colormap ,  Cursor , and  GContext ), or other resources that the client has created on this display, unless the close-down mode of the resource has been changed (see  XSetCloseDownMode ). Therefore, these windows, resource IDs, and other resources should never be referenced again or an error will be generated. Before exiting, you should call  XCloseDisplay  explicitly so that any pending errors are reported as  XCloseDisplay  performs a final  XSync  operation.  XCloseDisplay  can generate a  BadGC  error. AllPlanes(3X11), XFlush(3X11), XSetCloseDownMode(3X11) Xlib - C Language X Interface