to know whether a library is installed or not
 

How to know whether a library is installed or not in Linux?

find /usr/lib [libname]

If that doesn't bring up a result... you might not have it! Replace /usr/lib with / that will search the entire file-system.
If you use a distro with package management you best bet is to open the package manager and search within that.

I'm new to this forum. trying to understand LINUX and using RED HAD 8.X. Interested in knowing in how it works.

Hope to learn a lot and looking forward to work with all of you in the future.

Redhat uses "rpm" (Redhat package management). Redhat 8 is very old. I would suggest downloading a modern distro like fedora (based on redhat) and try it on a spare computer. It will teach you alot. If you must use Redhat 8, just do a search in the LQ.org Redhat section for package management stuff, also, open a terminal and type "man rpm" then press enter key. Read it, press "q" to exit. There is a "man" (manual) page for every command on your system.