watch allows you to repeat a command, in place, every n-seconds.
For example, if you're waiting to see when a web server log file is hit, you can run this watch command, using ls. By default it will run every 2 seconds.
$ watch ls logs -lart
The screen will not roll up. The information is just updated in place. (very handy).
Every 2.0s: ls logs -lart total 12 drwxr-xr-x 6 root root 4096 May 23 20:45 .. -rw-r--r-- 1 root root 0 May 24 14:06 error.log drwxr-xr-x 2 root root 4096 May 24 14:06 . -rw-r--r-- 1 root root 320 May 24 14:14 access.log
You can have the changes highlighted (-d),
alter the seconds to wait between updates (-n)
Press Ctrl-c to end the watch.