NS3.31 Installation in Ubuntu 20.04 | Step by Step Instructions

Installing #ns-3.31 in Ubuntu 20.04 - 64 bit OS.
Fresh installation of Ubuntu OS
$] sudo apt update
$] sudo apt install build-essential autoconf automake libxmu-dev
$] sudo apt install build-essential autoconf automake libxmu-dev python-pygraphviz cvs mercurial bzr git cmake p7zip-full python-matplotlib python-tk python-dev python-kiwi python-gnome2 python-gnome2-desktop qt4-dev-tools qt4-qmake qt4-qmake qt4-default gnuplot-x11 wireshark
extract to /home/pradeepkumar
To find what is your HOME, give the following command.
$] echo $HOME
$] cd ns-allinone-3.31/
$] ./build.py --enable-examples --enable-tests
$] cd ns-allinone-3.31/ns-3.31/
$] ./waf --run hello-simulator
This will display
"Hello Simulator"
Which indicates that ns3 is installed successfully.
$] ./waf --run first