[ale] How to tell if X is up?

[hirsch at mathcs.emory.edu]

Dan Newcombe <Newcombe at mordor.clayton.edu> wrote:
> On Wed, 21 Jul 1999 linuxhat at mailandnews.com wrote:
> > On 21 Jul 1999, Dave Brooks wrote:

> > Should have been more clear.  *from within a C program*, how can we tell
> > if  X is up and accepting connections on the local machine?  (also, from
> > within a script, the above would have to be just a little bit smarter....)
> 

> #include <X11/Xlib.h>
> #include <stdio.h>
> int main(int argc,char *argv)
> {
>   Display *display;
>   display=XOpenDisplay(NULL);
>   if(display==(Display *) NULL) {
>                 printf("Server not accepting connections\n");
>           return(1);
>   }
>   return(0);
> }
> 
> This works for me.  If I set my DISPLAY variable to a valid X server
> accepting connections, then it works.  If I set it to a machine without an
> X server (ie. NT :) then it prints the string.
> 
> This should be more portable than checking for the existence of a file
> someplace.

In the question he asks about the "local X server".  If your display variable
points to a remote server this code will test that server.  It is not clear to
me whether this is the desired behavior.  

--Michael