22.18 Clear Your Terminal for Security, to Stop Burn-in

The clear command reads your termcap or terminfo ( 5.2 ) entry to find out how to erase your screen, then it sends that command. If you're typing something confidential that other people shouldn't read, just type clear at a shell prompt when you can. Many UNIX programs let you do a shell escape ( 30.26 ) to run a single UNIX command - you can clear your screen that way, by typing something like !clear from inside the program.

NOTE: Some terminals and window systems have memories - scrolling buffers that save previous screens or the current one. The clear command probably won't clear those. Check your manual to find out how - or, if you're desperate, log off UNIX, then turn off your screen's power for a minute.

If you leave your desk for a long meeting or for the day, then remember that you didn't erase your screen, you can probably clear your screen from another user's terminal. (If your system has the tty -group-write protection ( 22.13 ) , then you'll have to log in or su ( 22.22 ) to your account from the other terminal first.) If the other terminal has the same terminal type, use the command:

who
 

% who

 | grep 



yourname




yourname

    ttyp3   Jun 24 10:44
% 

clear > /dev/ttyp3

If you're on a different type of terminal, you'll need to set the TERM environment variable temporarily ( 6.10 ) before you use that command.