cat'ing a binary messes up terminal - why?

[Thomas Sprinkmeier]

On Sat, 2006-10-28 at 10:53 +0930, Ben Petering wrote:
> Hi list,
> 
> I have a query, not important, I'm just curious. Hopefully someone
> understands what's happening here.
> 
> If I say
> $ cat /bin/login
> 
> for example, my terminal gets all messed up - i.e. typing '/bin/login'
> now appears as
> 
> $ /␉␋┼/┌⎺±␋┼
> 
> I suppose some kind of character table translation is broken or
> something... can someone explain in detail why this happens? I NEED to
> know :)
Hi Ben,

Terminals support all sorts of escape sequences to do things like
scroll, jump, change colour and, as you've found, character set.

Catting a binary file can randomly activate these things.

There are even some exploits based on specially crafted binary files, so
be careful :-)
"less" is a safer choice than "cat", "hexdump" is safer still.

The "reset" command can fix the mess. Failing that, just close the
terminal and start anther one.


Thomas