As far as I know, `tail -f <filename>` allows to continuously print newly appended data from one single file. 

What if I need to get content **from multiple files** located in multiple folders under the same parent folder, then filter that content if need be, and finally print it as a real-time stream, as new data gets appended to any one of the multiple monitored files?

EDIT: the operating system is RedHat Enterprise Linux 7.4