Displaying nmap result gradually as results are found
Solution 1:
Add this command line switch:
-v (Increase verbosity level) .
Increases the verbosity level, causing Nmap to print more information about
the scan in progress. Open ports are shown as they are found and completion
time estimates are provided when Nmap thinks a scan will take more than a few
minutes. Use it twice or more for even greater verbosity: -vv, or give a
verbosity level directly, for example -v3..
Source: https://nmap.org/book/man-output.html