I see a similar question on stackoverflow:

<https://stackoverflow.com/questions/1353253/linux-terminal-how-to-capture-or-watch-other-terminal-session>

Someone recommends [conspy](http://linux.die.net/man/1/conspy). However, it seems that conspy doesn't work for pts terminal. 

I also tried the way to use `strace` to get the keys pressed [here](http://www.edwiget.name/2013/06/how-to-monitor-a-linux-users-shell-in-real-time/#codesyntax_1), but I found the result quite difficult to read.

Does anyone have ideas about this?