hpux man page for xdisplaystring

XDisplayString()														  XDisplayString()

Name
  XDisplayString, DisplayString - get string passed to XOpenDisplay().

Synopsis
  char *XDisplayString(display)
	   Display *display;

Arguments
  display   Specifies a connection to an X server; returned from XOpenDisplay().

Returns
  The display name string.

Description
  XDisplayString() returns the string that was passed to XOpenDisplay() when the current display was opened.  On POSIX-conformant systems, if
  the passed string was NULL, it returns the value of the DISPLAY environment variable when the current display was opened.

  XDisplayString() is useful for printing error messages when XOpenDisplay() fails, and for applications that invoke the fork system call and
  want to open a new connection to the same display from the child process.

  The C language macro DisplayString() is equivalent and slightly more efficient.  XDisplayName() is also a similar function.

See Also
  XOpenDisplay().

Xlib - Macro Equivalents													  XDisplayString()