Chapter 2 MySQL C API Implementations

The MySQL C API is a C-based API that client applications written in C can use to communicate with MySQL Server. Client programs refer to C API header files at compile time and link to a C API library file at link time. The library comes in two versions, depending on how the application is intended to communicate with the server:

• libmysqlclient: The client version of the library, used for applications that communicate over a network connection as a client of a standalone server process.

• libmysqld: The embedded server version of the library, used for applications intended to include an embedded MySQL server within the application itself. The application communicates with its own private server instance.

  Note

  The libmysqld embedded server library is deprecated as of MySQL 5.7.19 and removed in MySQL 8.0.

Both libraries have the same interface. In terms of C API calls, an application communicates with a standalone server the same way it communicates with an embedded server. A given client can be built to communicate with a standalone or embedded server, depending on whether it is linked against libmysqlclient or libmysqld at build time.

To obtain the C API header and library files required to build C API client programs, install a MySQL Server distribution. Server distributions include both libmysqlclient and libmysqld.

You can install a binary distribution that contains the C API files pre-built, or you can use a MySQL Server source distribution and build the C API files yourself. Building MySQL Server also builds libmysqlclient and libmysqld; see Installing MySQL from Source. These client libraries cannot be built alone, but the optional -DWITHOUT_SERVER=ON CMake option is related.

The names of the library files to use when linking C API client applications depend on the library type and platform for which a distribution is built:

• On Unix (and Unix-like) systems, the static library is libmysqlclient.a. The dynamic library is libmysqlclient.so on most Unix systems and libmysqlclient.dylib on macOS.

  For distributions that include embedded server libraries, the corresponding library names begin with libmysqld rather than libmysqlclient.

• On Windows, the static library is mysqlclient.lib and the dynamic library is libmysql.dll. Windows distributions also include libmysql.lib, a static import library needed for using the dynamic library.

  For distributions that include embedded server libraries, the corresponding library names are mysqlserver.lib, libmysqld.dll, and libmysqld.lib.

  Windows distributions also include a set of debug libraries. These have the same names as the nondebug libraries, but are located in the lib/debug library. You must use the debug libraries when compiling clients built using the debug C runtime.

On Unix, you may also see libraries that include _r in the names. Before MySQL 5.5, these were built as thread-safe (re-entrant) libraries separately from the non-_r libraries. As of 5.5, both libraries are the same and the _r names are symbolic links to the corresponding non-_r names. There is no need to use the _r libraries. For example, if you use mysql_config to obtain linker flags, you can use mysql_config --libs in all cases, even for threaded clients. There is no need to use mysql_config --libs_r.