If you need to repeatedly run a command and view the output changes over time then check out my cli_watch.pl script. I was watching a RAID array rebuild slowly and needed a way to see the progress over time.
cli_watch.pl [--delay 15] [--line 3] command
Run my_command every 15 seconds:
cli_watch.pl --delay 15 'my_command | grep stuff'
Filter output to only line 2:
cli_watch.pl --line 2 'ping -c 1 192.168.5.222'