twGrabScreen
create screenshots without the need of confirmation
... limited by amount of available hard-drive space) by just using the configurable hotkey and no further need for any interaction.
Multithreading is used to enable capturing many frames in a short time interval.
Works with "normal" applications on the desktop as well as with OpenGL games (that's the only stuff I've tested).
Developed and tested on Linux only (may also work on other systems, you're free to try).
Note: Some keys may not be assignable as triggers for screenshot grabbing.