Setting up Modern GNU Flex on Debian based distros.

Installing dependencies

Run the following in a terminal emulator. sudo apt install -y autoconf automake make help2man m4 gcc g++ gettext bison texinfo libtool

git clone https://github.com/westes/flex.git

CD inside the directory

cd flex/

Run these commands one after the other and check errors for missing packages:

./autogen.sh
./configure
make -j`nproc`
sudo make install```