I need to run a Qt application in Batch mode, so basically I need to run it without GUI. 
I've already tried using QCoreApplication but my application relies on the existence of X11 window. So I need the GUI to open regularly, but I need to "hide" it from the user.
I know that I have the ability to create a virtual VNC and change the active display to the virtual VNC window.
I'm looking for a cleaner, simpler solution that will allow to suppress or "dump" the GUI output of the application.
If this helps for ideas, it will be used in a script written in Bash, Perl or Python.
As @utdmr suggested, that solved the problem.
I've thought that show() was also responsible for the signal/slot mechanism and other Qt and X11 functions. But apparently, the application works normally, just doesn't show the GUI. 
And that was exactly what I needed since it is a fully developed application and the effort to convert it to a console application was enormous.
Thanks utdmr :)
How to suppress a Qt GUI application?