“Watch Command” is to set a watcher on a linux command for real time monitoring of the command output.

Syntax as below

watch [OPTIONS] COMMAND

The -n (--interval), the option set the time interval between updates

watch -n INTERVAL_IN_SECONDS COMMAND

The -d (--difference), the option shows the changes between updates.

watch -d COMMAND

example. below command will show the log update every 2 seconds.

watch -n 2 "tail /tmp/some.log"

Good Read:

https://www.tutorialspoint.com/ubuntu/ubuntu_tutorial.pdf

https://ubuntu.com/tutorials/command-line-for-beginners#1-overview