export display in a shell script executed by Jenkins

[iostrym]

Hi,

We have a TCL script that has a GUI that is executed by Jenkins using a shell script in the job.

Then we have to use :

export DISPLAY=:<PORT_NUMBER>

I used things like that to try to avoid the use of a port number that is already used by someone else or by another job :

export DISPLAY=:`expr "$BUILD_NUMBER" + "100"`

Is there a clean way in the jenkins shell script to get a port_number that is free ? so that the job will never fail because of a port_number already existant...

thanks a lot.

[Mark Waite]

The xvnc plugin can start a VNC based X server at the start of your job, and stop it at the end of your job.  Most Linux distributions make it very easy to install Xvnc, then the plugin will use that installation of Xvnc to provide you a display server (and the DISPLAY environment variable).  I had very good results with that plugin.

There is also an Xvfb plugin which uses the X virtual frame buffer driver to do the same thing.  I haven't used it, but there are others who have used it with good results.

Mark Waite

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[iostrym]

Thanks a lot. But is the use of Xvfb plug-in more heavy than a simple export DISPLAY function ? in term of ressource utilization...

[iostrym]

ok i just realized that after the 

export DISPLAY=:<PORT_NUMBER>

I have the command :

Xvfb :`expr "$BUILD_NUMBER" + "100"` &

So using the plugin will have the same impact.

But... in the plugin I don't see anything to use a free port number... it is said that the port_number will be the number of the build. So there will be risk for build to abord if the port_number is take by another job...

[Dirk Heinrichs]

Am 07.01.2016 um 15:05 schrieb iostrym:

Thanks a lot. But is the use of Xvfb plug-in more heavy than a simple export DISPLAY function ? in term of ressource utilization...

Without it, setting DISPLAY for a Jenkins job doesn't make much sense.

Bye...

    Dirk

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[iostrym]

yes, sorry it was a mistake.

anyway, I don't succeed to let jenkins to chose the display number when using Xvbf plugin...

[Bap]

Try this: https://wiki.jenkins-ci.org/display/JENKINS/Port+Allocator+Plugin

[Bap]

Sorry, you asked for a free port number, but that's not really what you want.

As suggested, you should use
https://wiki.jenkins-ci.org/display/JENKINS/Xvfb+Plugin

[iostrym]

thanks a lot. I didn't see this option "Let Xvfb choose display name"

:)