A /dev/null equivilent for DISPLAY when the display is just noise.

Question

I'm running a java app which creates a visual display of some of the things it is doing, while it is doing it. However, I'm want to run this in a script that won't have a display to attach to. In the current environment, there isn't even a DISPLAY environment variable set. I tried to simply set my DISPLAY to :0.0. But that doesn't exist. I don't really care about the display. I just want the app to process the files silently.

Since I can't just turn the display off(not my app), I'm left with trying to get around the need for display.

Is there a black hole that I can send the DISPLAY to? an equivalent to /dev/null?

I searched around for a bit on the web, but the words I could think of to use: "display" "null" "disregard" etc are all two generic to get me to an answer.

This is the middle of a larger script, so I want the rest of the output to stdout to be available.

Answer 1

There's a headless X server called Xfb (or Xvfb, I can't remember off the top of my head and it's been a long time since I've ever had to do something like this). It's basically what you need since it accepts X clients but basically does nothing with the data from them.

If you can't find that, then another possibility would be to use a spare PC with a full CygWin install. It comes with a full-blown X server which you could connect your application to (and just ignore it). You could even set it up as the corporate /dev/null DISPLAY.

But I'd look into Xfb first.

Answer 2

Can you run a VM on the target machine? Then you could set your DISPLAY to that. Or you could try vnc (currently on a machine which doesn't allow this or I'd try it...).

Answer 3

You can use Xvfb, as noted above. That way, you will never see the output (you can use a tool to take screenshots, though).

http://en.wikipedia.org/wiki/Xvfb http://packages.debian.org/sid/xvfb

Or you could set up a VNC server. Under Linux, a VNC server is implemented as a special X server that can be accessed via VNC, insstead of displaying on a local monitor. That gives you a headless X server, with the added bonus that you can connect to it via VNC just in case you do need to see what's going on.

http://www.tightvnc.com/vncserver.1.html

vncserver is a nice wrapper script for (tight)VNC, which makes starting a VNC server a breeze. Most distros should install it by default.

Answer 4

If it's a java program you can use the headless mode to run the application.

Try to run it with -Djava.awt.headless=true parameter, like this if it's a jar file:

java -Djava.awt.headless=true -jar jarfile.jar

More about headless mode...