How can I printscreen in X11 Environment? I use Wireshark and it runs under X11 environment I want take some screenshot from wireshark windows but 
cmd + shift + 3  or cmd + shift + 4 or ... didn't work there is there any way that I could take some screen shot in X11 environment?
Click to the desktop or any other application, and then press ⌘ + ⇧ + 3.

With this method Wireshark will loose the focus and you can grab the whole screen.