cat /dev/tty?

yoshiznit123 · 12-14-2005, 12:00 PM

Hi, I was just messing around on my linux box and I tried 'cat /dev/tty2'. Then I tried logging in on that terminal, and when I entered my password it appeared in the output of the first terminal... I was wondering if this was normal and/or why it happens. Thanks :-)

int0x80 · 12-14-2005, 12:05 PM

cat just dumps the contents of whatever you feed it. In Unix systems, any output can become input. You may also find the following interesting:

cat /dev/input/mice (or whatever device your mouse is) then move the mouse around
cat /dev/urandom

yoshiznit123 · 12-14-2005, 12:18 PM

Cool, but why does cat only output the password when I try to login, not the username or anything?

Wells · 12-14-2005, 12:44 PM

Yes, this is true. What happens is that everything input into that particular tty is spit out to the catenation you are performing. Note that, unless you are root, you can only do this on tty's that you are currently logged into, because the permissions are set that way. Yes, security is taken care of for this sort of thing.