It might just be that the dynamic loader hasn't realized yet that you've added QuantLib. Try adding the line
/usr/local/lib
to /etc/ld.so.conf
(if it's not already there) and then run
sudo ldconfig
On your system there should be man pages for both ld.so
and ldconfig
if you want to understand what you're doing, which is always a good proposition. Never execute commands given by strangers on the internet, especially in sudo
mode :)
After you do the above, you should be able to load libQuantLib
.