...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
This example assumes you have gone through the setup.
/** * This example demonstrates how to connect to MySQL using a UNIX socket. * * It uses C++20 coroutines. If you need, you can backport * it to C++11 by using callbacks, asio::yield_context * or sync functions instead of coroutines. */ #include <boost/mysql/any_address.hpp> #include <boost/mysql/any_connection.hpp> #include <boost/mysql/error_with_diagnostics.hpp> #include <boost/mysql/results.hpp> #include <boost/asio/awaitable.hpp> #include <boost/asio/co_spawn.hpp> #include <boost/asio/io_context.hpp> #include <iostream> #include <string_view> namespace mysql = boost::mysql; namespace asio = boost::asio; // The main coroutine asio::awaitable<void> coro_main( std::string_view unix_socket_path, std::string_view username, std::string_view password ) { // Create a connection. // Will use the same executor as the coroutine. mysql::any_connection conn(co_await asio::this_coro::executor); // The socket path, username, password and database to use. // server_address is a variant-like type. Using emplace_unix_path, // we can specify a UNIX socket path, instead of a hostname and a port. // UNIX socket connections never use TLS. mysql::connect_params params; params.server_address.emplace_unix_path(std::string(unix_socket_path)); params.username = username; params.password = password; params.database = "boost_mysql_examples"; // Connect to the server co_await conn.async_connect(params); // The connection can now be used normally mysql::results result; co_await conn.async_execute("SELECT 'Hello world!'", result); std::cout << result.rows().at(0).at(0) << std::endl; // Notify the MySQL server we want to quit, then close the underlying connection. co_await conn.async_close(); } void main_impl(int argc, char** argv) { if (argc != 3 && argc != 4) { std::cerr << "Usage: " << argv[0] << " <username> <password> [<socket-path>]\n"; exit(1); } // If not provided, use the default UNIX socket path, // compatible with most UNIX systems. const char* socket_path = argc >= 4 ? argv[3] : "/var/run/mysqld/mysqld.sock"; // Create an I/O context, required by all I/O objects asio::io_context ctx; // Launch our coroutine asio::co_spawn( ctx, [=] { return coro_main(socket_path, argv[1], argv[2]); }, // If any exception is thrown in the coroutine body, rethrow it. [](std::exception_ptr ptr) { if (ptr) { std::rethrow_exception(ptr); } } ); // Calling run will actually execute the coroutine until completion ctx.run(); std::cout << "Done\n"; } int main(int argc, char** argv) { try { main_impl(argc, argv); } catch (const boost::mysql::error_with_diagnostics& err) { // Some errors include additional diagnostics, like server-provided error messages. // Security note: diagnostics::server_message may contain user-supplied values (e.g. the // field value that caused the error) and is encoded using to the connection's character set // (UTF-8 by default). Treat is as untrusted input. std::cerr << "Error: " << err.what() << ", error code: " << err.code() << '\n' << "Server diagnostics: " << err.get_diagnostics().server_message() << std::endl; return 1; } catch (const std::exception& err) { std::cerr << "Error: " << err.what() << std::endl; return 1; } }