Copying the GNU screen scrollback buffer to a file (extended hardcopy)
To write the entire contents of the scrollback buffer to a file, type
Ctrl + A and : to get to command mode, then
hardcopy -h <filename>
In older versions of screen, if you just do hardcopy -h, it just writes to the file -h. This was fixed in version 4.2.0, so hardcopy -h writes to hardcopy.N where N is the current window number.
Press Ctrl+A :bufferfile /tmp/somefile.txt ENTER, and then Ctrl+A >
This will write the current contents of the buffer to the named file.