Sometime there is need to watch a directory for certain file, i mean you want to keep watch on directory. Following command can serve your purpose
root#watch -d ls -l
Above command will update screen after every 2 second (Default is 2 sec) and present you with the difference (-d option).
If you want to monitor network connection update using watch command you can use in following way
root#watch -d 'netstat -an'
Watch command allow you to watch program output changes over time , by default that time is 2 second but you change that time using -n option.use -d option if you want to changes in successive update but if you want to see cumulative changes use -c option.