Any options that may be given with the mysqld
      server daemon, may be used with an embedded server library. Server
      options may be given in an array as an argument to the
      mysql_library_init(), which
      initializes the server. They also may be given in an option file
      like my.cnf. To specify an option file for a
      C program, use the --defaults-file
      option as one of the elements of the second argument of the
      mysql_library_init() function. See
      mysql_library_init(), for more information on the
      mysql_library_init() function.
    
      Using option files can make it easier to switch between a
      client/server application and one where MySQL is embedded. Put
      common options under the [server] group. These
      are read by both MySQL versions. Client/server-specific options
      should go under the [mysqld] section. Put
      options specific to the embedded MySQL server library in the
      [embedded] section. Options specific to
      applications go under section labeled
      [ApplicationName_SERVER]. See
      Section 4.2.2.2, “Using Option Files”.