21.8.4.3. Running C API Client Programs

Undefined-reference errors might occur at runtime when you try to execute a MySQL program. If these errors specify symbols that start with mysql_ or indicate that the libmysqlclient library cannot be found, it means that your system cannot find the shared libmysqlclient.so library. The solution to this problem is to tell your system to search for shared libraries in the directory where that library is located. Use whichever of the following methods is appropriate for your system:

Add the path of the directory where libmysqlclient.so is located to the LD_LIBRARY_PATH or LD_LIBRARY environment variable.
On Mac OS X, add the path of the directory where libmysqlclient.dylib is located to the DYLD_LIBRARY_PATH environment variable.
Copy the shared-library files (such as libmysqlclient.so) to some directory that is searched by your system, such as /lib, and update the shared library information by executing ldconfig. Be sure to copy all related files. A shared library might exist under several names, using symlinks to provide the alternate names.

If the application is linked to the embedded server library, runtime error messages will indicate the libmysqld rather than libmysqlclient library, but the solution to the problem is the same as just described.