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     XOpenDisplay(3X)                            XOpenDisplay(3X)



     NAME
          XOpenDisplay, XCloseDisplay - connect or disconnect to
          X server

     SYNOPSIS
          Display *XOpenDisplay(display_name)
                char *display_name;

          XCloseDisplay(display)
                Display *display;

     ARGUMENTS
          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 UNIX-based system,
                    if the display_name is NULL, it defaults to
                    the value of the DISPLAY environment
                    variable.

     DESCRIPTION
          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, UNIX domain, or DECnet communications
          protocols.  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 unix and a single colon (:) separates
          it from the display number, XOpenDisplay connects using
          UNIX domain IPC 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



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     XOpenDisplay(3X)                            XOpenDisplay(3X)



          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.

     SEE ALSO
          Xlib Programming Manual


































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