# build shared library
gcc -fPIC -shared -Wl,-soname,libhello.so.1 -olibhello.so.1.0.3 libhello.c

# install shared library
sudo mkdir -p /opt/myfirma/lib
sudo cp libhello.so.1.0.3 /opt/myfirma/lib

# add custom path to dynamic loader search path
echo "/opt/myfirma/lib" | sudo tee /etc/ld.so.conf.d/myfirma.conf

# refresh dynamic loader cache
sudo ldconfig

# verify custom library is in cache
/sbin/ldconfig -p | grep libhello.so.1

# compile program using custom library
ln -s /opt/myfirma/lib/libhello.so.1.0.3 libhello.so
gcc -L. -ohello hello.c -lhello
rm libhello.so