clear full-screen in script and get the previous prompts after exiting script

Today I was using glance tool in my office to monitor CPU utilization.When I run glance from terminal ,the command clears the screen and after all the work when I quit back to the terminal,the previous prompts are still there on my screen.I mean that I can see all the previous lines.My question is how is this effect of clearing screen achieved.If they had used command like clear,It should have cleared the whole screen,how did they manage to get back all the previous prompts ? I want to implement the same feature for some of my scripts.

What’s the difference between “realpath” and “readlink -f”

I’ve read a lot about realpath command and how it has been deprecated with the readlink -f being now recommended. I have also seen in some places that the reason why realpath was introduced was for the lack of such functionality in readlink and that once it has been introduced, realpath was no longer needed and its support discontinued by most OS vendors.