Like tools such as whiptail and dialog, zenity allows for easy creation of GUIs, though it has fewer features than more complex GUI creation tools.
Other scripting languages such as Perl and Python can be used to construct full-scale GUI applications, but the zenity program enables a shell script to interact with a GUI user.... [The] user interface is not as refined as one that could be provided by a full-featured GUI application, but it is perfectly suitable for simple interactions.
As of 2012[update], Zenity is available for Linux, BSD and Windows. A Zenity port to Mac OS X is available in MacPorts; the homebrew-zenity project has been discontinued.
Zenity does not possess any built-in scripting capabilities and it must, therefore, rely on an interpreter for processing. To create a script that runs on more than one platform without extensive modifications, it would be best to use an interpreter that is available on the widest range of operating systems. One option is Python in combination with the PyZenity library.