Shared Libraries in 3 steps

What are Shared Libraries?

• Libraries with the .so extension which can be shared among multiple programs thus greatly reducing the memory footprint.
• Libraries can be updated without affecting the user code.
• Multiple versions of libraries can stay together and the user code can link to required version.2.
    

How to create a shared library?

• First create a test.c file with the function implementation.
• Create an object file test.o  

          gcc -c test.c

• Create the shared library using the following command

          gcc -shared -o libtest.so test.o -Lpwd

   
How to use a shared library?

• First write a c code main.c that uses the function used in test.c.
• Put the location of library in LD_LIBRARY_PATH
• Now we need to compile the main.c with the linking info about the shared library.

         gcc -o test main.c -ltest     //Note that here ltest corresponds to libtest.so