17.10 printscreen snipping tool

You can check it out from Settings:

Device > keyboard > keyboard shortcuts > screenshots

You can copy it to clipboard without saving using Ctrl+Alt+PrtScr

In the Gnome-* environment that 17.10 has, it looks like (shift+printscrn) or just (printscrn) automatically saves in the default folder(Pictures or so) without giving an option to just copy to clipboard(and discard the file without saving it) and/or save it in whatever location needed. This along with so many other things have made life uneasy for the ones comfortable with the Unity-ish features which provided the above.

I wanted this as well that was with the good old Unity. Now, after having upgraded to 17.10, the whole look and feel Gnome-change, and what not, it became a major inconvenience and felt a lot like out of the place. So, I really wanted to get the 17.04 Unity look and feel back along with all the Unity panel operations, etc, so I removed Gnome-* specific stuff, installed Unity - desktop, session, greeter, lightdm, indicator-sound, unity-control-center, reinstalled graphics drivers(Nvidia in my case), with couple of attempts(reboot, etc), I got everything back like the old 17.04 had including the screenshot/clipboard copying, etc.

Also, I didn't want the big central sound level indicator that appears at the bottom of the screen masking the screen whenever I increased/decreased/muted volume either using the multimedia keys or using the mouse scroll wheel over the top bar sound icon. Tried so many things and looked around in the internet to get rid of it. But none, helped. Also, Gnome-based environment looked very sluggish when compared to that of Unity. Going back to Unity fixed this as it was in 17.04.

Kudos to the oldie, Unity as long as it works and lasts with 17.10 Ubuntu and future versions!

Try Ctrl+Shift+Prtscr, it should copy a selected area to clipboard and will not save it to file.

The other part of your problem may get solved from here :- https://askubuntu.com/a/191539/611441