while true; do uptime; sleep 5;done

Obviously, this eventually clears your terminal history. BASH to rescue! My noop script solves this problem. (Please see comments, there maybe a better solution, thanks David!) noop, standing for no operation, is a processor instruction and is common in protocols. You may find it interesting, that exploit code is filled with NOP’s. The operation increases your chances of exploiting buffer overflows

The source:

$ cat /usr/bin/noop
#!/bin/bash
backspace() {
        echo -e "\b\c"
}
cleanup() {
        backspace
        exit
}
trap "cleanup" 2
while :
do
        num=${RANDOM:0:1}
        printf $num
        sleep ".$num"
        backspace
done

For the hell of it, I made a video of noop in action.

If your wondering how the script works, here is a quick explanation. The script defines two functions. backspace and cleanup. Backspace prints the special characters \b and \c.  Backslash b is a backspace, and backslash c, stops echo from printing a trailing newline:

backspace() {
        echo -e "\b\c"
}

The cleanup function prints a backspace and then exits.  The cleanup function is run by trap when it receives a SIGINT (2):

cleanup() {
        backspace
        exit
}
trap "cleanup" 2

The main body of the script, is an infinite loop which generates, a random number using the special variable $RANDOM. This random is assigned to the variable num, utilizing only the first digit. After printing that number, the script sleeps num tenths of seconds, and the backspace function is called:

while :
do
        num=${RANDOM:0:1}
        printf $num
        sleep ".$num"
        backspace
done