opencv already present

#https://www.pyimagesearch.com/2016/04/18/install-guide-raspberry-pi-3-raspbian-jessie-opencv-3/
# sudo raspi-config  #use all of the SD card.
mydir="/home/pi/lfs"
mycores="-j4"
set -euf -o pipefail      #sipb.mit.ede safe scripting tutorial

function createLFS {
 ! [ -d "$mydir" ] &&  mkdir "$mydir"
}

# sudo apt update; sudo apt-get upgrade; sudo rpi-update
sudo apt purge wolfram-engine; sudo apt purge libreoffice
sudo apt install     -y build-essential git cmake pkg-config
sudo apt-get         -y  install python2.7-dev python3-dev
sudo apt install     -y  libjpeg-dev libtiff5-dev libjasper-dev libpng12-dev
sudo apt-get install -y  libavcodec-dev libavformat-dev libswscale-dev libv4l-dev
sudo apt install     -y  libavutil-dev  libavdevice-dev
sudo apt-get install -y libxvidcore-dev libx264-dev
sudo apt-get install -y libgtk2.0-dev
sudo apt-get install -y libatlas-base-dev gfortran
wget -nc https://bootstrap.pypa.io/get-pip.py; sudo python get-pip.py
sudo pip2 install  numpy
sudo pip3 install  numpy

cd "$mydir"
# files copied over already into lfs folder
#wget -O opencv_contrib.zip https://github.com/Itseez/opencv_contrib/archive/3.3.0.zip
#unzip opencv_contrib.zip

################# SET SWAPFILE SIZE ##############
# cd /etc/dphys-swapfile
# https://www.bitpi.co/2015/02/11/how-to-change-raspberry-pis-swapfile-size-on-rasbian/
# edit file
# CONF_SWAPSIZE=1024  # set back to 100 after opencv is installed
# sudo /etc/dphys-swapfile swapoff
# sudo /etc/dphys-swapfile swapon

#git clone https://github.com/opencv/opencv.git
cd opencv
#git checkout 3.3.0
git checkout master
git pull
# rm -rf build
mkdir build && cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE \
      -D CMAKE_INSTALL_PREFIX=/usr/local \
      -D OPENCV_EXTRA_MODULES_PATH="$mydir/opencv_contrib-3.3.0/modules" \
      -D BUILD_TESTS=OFF  ..
#      -D INSTALL_PYTHON_EXAMPLES=ON \
#      -D BUILD_EXAMPLES=ON ..
#      -D PYTHON_EXECUTABLE=/usr/bin/python3.5 \
#      -D PYTHON_PACKAGES_PATHS=/usr/local/lib/python3.5/dist-packages \
#      -D PYTHON_NUMPY_INCLUDE_DIRS=/usr/local/lib/python3.5/dist-packages/numpy/core/include ..  \
#      -D ENABLE_NEON=ON \
#      -D ENABLE_VFPV3=ON \

make -j4; sudo make install; sudo ldconfig
#go back to swap file reset to 100mb!

function post_install_opencv {
if [ ! -e "/etc/ld.so.conf.d/opencv.conf" ]; then
 sudo sh -c 'echo "/usr/local/lib" >> /etc/ld.so.conf.d/opencv.conf'
fi
sudo ldconfig
echo "finding the cv2.so package at usr/local/lib"
find /usr/local/lib/ -type f -name "cv2*.so"
# outputs
#/usr/local/lib/python2.7/dist-packages/cv2.so
#/usr/local/lib/python3.5/dist-packages/cv2.cpython-35m-x86_64-linux-gnu.so
#cd /usr/local/lib/python3.5/dist-packages
echo "moving(renaming) the x86 cv2 file to cv2.so"
cd /usr/local/lib/python3.5/dist-packages
sudo mv cv2.cpython-35m-x86_64-linux-gnu.so cv2.so
#ln -s /usr/local/lib/python3.5/dist-packages/cv2.cpython-36m-x86_64-linux-gnu.so cv2.so
}


#https://www.pyimagesearch.com/2016/04/18/install-guide-raspberry-pi-3-raspbian-jessie-opencv-3/
# make certain that cv2.so in site packages are in both python2 and 3 . See web for details.