setterm -dump N will dump the contents of the screen of /dev/ttyN to a file screen.dump in the current directory. See setterm(1).
The current contents of the screen of /dev/ttyN can be accessed using the device /dev/vcsN (where `vcs' stands for `virtual console screen'). For example, you could have a clock program that displays the current time in the upper right hand corner of the console screen (see the program vcstime in kbd-1.04.tar.gz). Just dumping the contents goes with cat /dev/vcsN. These device files /dev/vcsN do not contain newlines, and do not contain attributes, like colors. From a program it is usually better to use /dev/vcsaN (`virtual console screen with attributes') instead - it starts with a header giving the number of rows and columns and the location of the cursor. See vcs(4).