Is it possible to add widgets to my desktop using bash?

It is not possible to do that yet, but when KDE 4.4 comes out, plasma will be scriptable using javascript. You can read more about it here:

http://aseigo.blogspot.com/2009/09/scripting-plasma-desktop.html

Alec YEA! That's exactly what I need!
So what is the release date ? At least approximately ? Cannot find it...

It's currently scheduled for February 6.

Holy shi! But that's quite too long! Is there any workaround?
I guess plasma saves information about widgets somewhere, maybe it's possible to hack it somehow?
It's not necessary to do it on the fly, when plasma is already working.

Neosano wrote:Holy shi! But that's quite too long!

Blame it on Ubuntu's Mark Shuttleworth - synchronized half-year release cycles were his idea! :p

Neosano wrote:Is there any workaround?
I guess plasma saves information about widgets somewhere, maybe I can hack it somehow?
It's not necessary to do it on the fly, when plasma is already working.

I'm not sure what exactly you want to do (If you told us more, there could be better solutions :) but plasma stores its plasmoid configuration in this file:

~/.kde4/share/config/plasma-desktop-appletsrc

Unfortunately, it's not really intended to be editable...

Note that Plasma needs to be stopped when editing that configuration file, as otherwise it will overwrite all changes on shutdown.

If a PPA is available, you could try running Trunk, which is reasonably stable currently ( although you will encounter more crashes than a normal KDE release )