compile and link C/CPP programs on Mac

ref: https://stackoverflow.com/questions/29987716/cannot-use-gsl-library-on-macos-ld-symbols-not-found-for-architecture-x86-6

Indeed, as @trojanfoe and @bergercookie said you have to compile your file and then link it to the library. As explained in compile and link, for that particular example: First compile the file: gcc -Wall -I/usr/local/include -c example.c -o example.o second, link it to the library: gcc -L/usr/local/lib example.o -lgsl -o example where of course, /usr/local/lib should be replaced for the path where you have gsl installed. The example file is excutable. EDIT: in macOS, from Yosemite the default location for the installation is /opt/local/lib (and /opt/local/include)