MariaDB 'C' Api

MariaDB 'C' Api
From; https://mariadb.com/kb/en/mariadb-connector-c/


github Mariadb Examples Build Applications Build C API Client Pgms C-API Funcs Examples Reading Data Compiling Clients On unix Compiling Clients On Win Debug Linking Client Lib Privileges Connect Options Errors Types & Defns Types Structs Getting Data MySqlAPI	About MariaDB Connector/C Overview of MariaDB Connector/C. Building and Installing MariaDB Connector/C Configuring MariaDB Connector/C with Option Files Configuring MariaDB Connector/C with my.cnf and other option files. MariaDB Connector/C API Functions MariaDB Connector/C API Prepared Statement Functions MariaDB client API prepared statement functions MariaDB Connector/C Data Structures Public data structures used by MariaDB Connector/C. MariaDB Connector/C Types and Definitions Types and definitions provided by MariaDB Connector/C. MariaDB Connector/C Plugins MariaDB Connector/C functionality can be extended via loadable (or statical...


Listening On a socket Listening On TCP Cmds Out of Sync

Check Out mysqladmin



Connecting
Sharing a connection over multiple threads is not a good idea, since you have to
handle all kind of problems in your application: Transaction safety, protocol
buffers etc.

mysql_init() API function initializes a connection handle (MYSQL) which will be
used to connect to a server via mysql_real_connect(). Trying to connect with the
same handle again will result in an error (CR_ALREADY_CONNECTED=2058).

Using one connection per thread is the better solution. If threads don't use the
connection all the time, use a connection pool (e.g. by using Connector/C++).


Who is listening on a unix socket:
netstat -lpn



Listening On TCP
netstat -antp | grep LIST



3.2 Building C API Client Programs
This section provides guidelines for compiling C programs that use the MySQL
C API.

Compiling MySQL Clients on Unix
Compiling MySQL Clients on Microsoft Windows
Troubleshooting Problems Linking to the MySQL Client Library




Commands out of sync
If you get Commands out of sync; you can't run this command now in your client
code, you are calling client functions in the wrong order.

This can happen, for example, if you are using mysql_use_result()
and try to execute a new query before you have called mysql_free_result().
It can also happen if you try to execute two queries that return data without 
calling mysql_use_result() or mysql_store_result() in between. 



Compiling MySQL Clients on Unix
The examples here use gcc as the compiler. A different compiler might be
appropriate on some systems (for example, clang on macOS or FreeBSD, or Sun
Studio on Solaris). Adjust the examples as necessary.

You may need to specify an -I option when you compile client programs that
use MySQL header files, so that the compiler can find them. For example, if
the header files are installed in /usr/local/mysql/include, use this option
in the compile command:
	-I/usr/local/mysql/include

You can link your code with either the dynamic or static MySQL C client
library. The dynamic library base name is libmysqlclient and the suffix
differs by platform (for example, .so for Linux, .dylib for macOS). The
static library is named libmysqlclient.a on all platforms.

MySQL clients must be linked using the -lmysqlclient option in the link
command. You may also need to specify a -L option to tell the linker where
to find the library. For example, if the library is installed in
/usr/local/mysql/lib, use these options in the link command:
	-L/usr/local/mysql/lib -lmysqlclient

The path names may differ on your system. Adjust the -I and -L options as
necessary.

To make it simpler to compile MySQL programs on Unix, use the mysql_config
script. See mysql_config — Display Options for Compiling Clients.

mysql_config displays the options needed for compiling or linking:
	mysql_config --cflags
mysql_config --libs

You can invoke those commands at the command line to get the proper options
and add them manually to compilation or link commands. Alternatively,
include the output from mysql_config directly within command lines using
backticks:
	gcc -c `mysql_config --cflags` progname.c
gcc -o progname progname.o `mysql_config --libs`

On Unix, linking uses dynamic libraries by default. To link to the static
client library instead, add its path name to the link command. For example,
if the library is located in /usr/local/mysql/lib, link like this:
	gcc -o progname progname.o /usr/local/mysql/lib/libmysqlclient.a

Or use mysql_config to provide the path to the library:
	gcc -o progname progname.o `mysql_config --variabl
e=pkglibdir`/libmysqlclient.a

mysql_config does not currently provide a way to list all libraries needed
for static linking, so it might be necessary to name additional libraries on
the link command (for example, -lnsl -lsocket on Solaris). To get an idea
which libraries to add, use mysql_config --libs and ldd libmysqlclient.so
(or otool -L libmysqlclient.dylib on macOS).

pkg-config can be used as an alternative to mysql_config for obtaining
information such as compiler flags or link libraries required to compile
MySQL applications. For example, the following pairs of commands are
equivalent:
	mysql_config --cflags
pkg-config --cflags mysqlclient

mysql_config --libs
pkg-config --libs mysqlclient

To produce flags for static linking, use this command:
	pkg-config --static --libs mysqlclient

For more information, see Section 3.3, “Building C API Client Programs
Using pkg-config”.



Compiling MySQL Clients on Microsoft Windows

To specify header and library file locations, use the facilities provided by
your development environment.

To build C API clients on Windows, you must link in the C client library, as
well as the Windows ws2_32 sockets library and Secur32 security library.

You can link your code with either the dynamic or static MySQL C client
library:

 The dynamic library is named libmysql.dll. In addition, the libmysql.lib
static import library is needed for using the dynamic library.

 The static library is named mysqlclient.lib. To link with the static C
client library, the client application must be compiled with the same
version of Visual Studio used to compile the C client library (which is
Visual Studio 2013 for the static C client library built by Oracle).

When using the Oracle-built MySQL C client library, follow these rules when
it comes to linking the C runtime for your client application:

 For the MySQL C client library from a Community distribution of MySQL:

 For MySQL 5.7.18 and higher: Always link dynamically to the C runtime (use
the /MD compiler option), whether you are linking to the static or dynamic C
client library. Also, target hosts running the client application must have
the Visual C++ Redistributable for Visual Studio 2013 installed.

 For MySQL 5.7.17 and lower:

 If linking to the static C client library, link statically to the C runtime
(use the /MT compiler option).

 If linking to the dynamic C client library, link either statically or
dynamically to the C runtime (use either /MT or /MD compiler option).

 For the MySQL C client library from a Commercial distribution of MySQL:

 If linking to the static C client library, link statically to the C runtime
(use the /MT compiler option).

 If linking to the dynamic C client library, link either statically or
dynamically to the C runtime (use either /MT or /MD compiler option).

In general, when linking to a static MySQL C client library, the client
library and the client application must use the same compiler options when
it comes to linking the C runtime—that is, if your C client library is
compiled with the /MT option, your client application should also be
compiled with the /MT option, and so on (see the MSDN page describing the C
library linking options for more details). Follow this rule when you build
your own static MySQL C client library from a source distribution of MySQL
and link your client application to it.
Note

Debug Mode: Because of the just-mentioned linking rule, you cannot build
your application in debug mode (with the /MTd or /MDd compiler option) and
link it to a static C client library built by Oracle, which is not built
with the debug options. Instead, you must build the static client library
from source with the debug options.



Troubleshooting Problems Linking to 
the MySQL Client Library

The MySQL client library includes SSL support built in. It is unnecessary to
specify either -lssl or -lcrypto at link time. Doing so may in fact result
in problems at runtime.

If the linker cannot find the MySQL client library, you might get undefined
-reference errors for symbols that start with mysql_, such as those shown
here:
	/tmp/ccFKsdPa.o: In function `main':
/tmp/ccFKsdPa.o(.text+0xb): undefined reference to `mysql_init'
/tmp/ccFKsdPa.o(.text+0x31): undefined reference to `mysql_real_connect'
/tmp/ccFKsdPa.o(.text+0x69): undefined reference to `mysql_error'
/tmp/ccFKsdPa.o(.text+0x9a): undefined reference to `mysql_close'

You should be able to solve this problem by adding -Ldir_path -lmysqlclient
at the end of your link command, where dir_path represents the path name of
the directory where the client library is located. To determine the correct
directory, try this command:
	mysql_config --libs

The output from mysql_config might indicate other libraries that should be
specified on the link command as well. You can include mysql_config output
directly in your compile or link command using backticks. For example:
	gcc -o progname progname.o `mysql_config --libs`

If an error occurs at link time that the floor symbol is undefined, link to
the math library by adding -lm to the end of the compile/link line.
Similarly, if you get undefined-reference errors for other functions that
should exist on your system, such as connect(), check the manual page for
the function in question to determine which libraries you should add to the
link command.

If you get undefined-reference errors such as the following for functions
that do not exist on your system, it usually means that your MySQL client
library was compiled on a system that is not 100% compatible with yours:
	mf_format.o(.text+0x201): undefined reference to `__lxstat'

In this case, you should download a source distribution for the latest
version of MySQL and compile the MySQL client library yourself. See
Installing MySQL from Source.


C & C++ Connectors



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Setup for Examples

Topics on this page:
    Overview
    Create the Schema
    Create the User
        Password Guidance



Overview
Examples in this MariaDB Connector/C documentation depend on a database test and table contacts.

Create the Schema

Create the example database and table:
	CREATE DATABASE IF NOT EXISTS test;

    CREATE TABLE test.contacts (
       id INT PRIMARY KEY AUTO_INCREMENT,
       first_name VARCHAR(25),
       last_name VARCHAR(25),
       email VARCHAR(100)) ENGINE=InnoDB;



Create the User
Create a user db_user with privileges to execute the examples:
	CREATE USER IF NOT EXISTS db_user@192.0.2.1
IDENTIFIED BY 'db_user_password';

	GRANT ALL PRIVILEGES ON test.* TO db_user@192.0.2.1;



Password Guidance
Passwords should meet your organization's password policies. If your MariaDB Enterprise Server instance has a password validation plugin installed, the password must also meet the configured requirements.

By default, MariaDB Enterprise Server installs the simple_password_check plugin, configured with system variables:

simple_password_check_digits
simple_password_check_letters_same_case
simple_password_check_minimal_length
simple_password_check_other_characters system variables.