Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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MYSQL *mysql_real_connect(MYSQL *mysql, const char *host, const char *user, const char
*passwd, const char *db, unsigned int port, const char *unix_socket, unsigned long client_flag)
mysql_real_connect() attempts to establish a connection to a MySQL database
engine running on host. mysql_real_connect() must complete successfully before you can execute any
other API functions that require a valid MYSQL connection handle structure.
The parameters are specified as follows:
For the first parameter, specify the address of an existing MYSQL
structure. Before calling mysql_real_connect(),
call mysql_init() to initialize the MYSQL
structure. You can change a lot of connect options with the mysql_options() call. See Section
22.8.7.49, "mysql_options()".
The value of host may be either a host name or an IP
address. If host is NULL or the string "localhost", a connection to the local host is assumed. For Windows, the
client connects using a shared-memory connection, if the server has shared-memory connections enabled.
Otherwise, TCP/IP is used. For Unix, the client connects using a Unix socket file. For local
connections, you can also influence the type of connection to use with the MYSQL_OPT_PROTOCOL
or MYSQL_OPT_NAMED_PIPE options to mysql_options(). The type of connection must be supported by the
server. For a host value of "." on Windows,
the client connects using a named pipe, if the server has named-pipe connections enabled. If named-pipe
connections are not enabled, an error occurs.
The user parameter contains the user's MySQL login ID.
If user is NULL or the empty string "", the current user is assumed. Under Unix, this is the current login
name. Under Windows ODBC, the current user name must be specified explicitly. See the Connector/ODBC
section of Chapter
22, Connectors and APIs.
The passwd parameter contains the password for user. If passwd is NULL, only entries in the user table for the
user that have a blank (empty) password field are checked for a match. This enables the database
administrator to set up the MySQL privilege system in such a way that users get different privileges
depending on whether they have specified a password.
Do not attempt to encrypt the password before calling mysql_real_connect(); password encryption is handled
automatically by the client API.
The user and passwd
parameters use whatever character set has been configured for the MYSQL
object. By default, this is latin1, but can be changed by calling mysql_options(mysql, MYSQL_SET_CHARSET_NAME, "
prior to connecting. charset_name")
db is the database name. If db is not NULL, the connection sets the default
database to this value.
If port is not 0, the value is used as the port number
for the TCP/IP connection. Note that the host parameter determines the type
of the connection.
If unix_socket is not NULL, the string specifies the socket or named pipe to use. Note that the
host parameter determines the type of the connection.
The value of client_flag is usually 0, but can be set
to a combination of the following flags to enable certain features.
| Flag Name | Flag Description |
|---|---|
CAN_HANDLE_EXPIRED_PASSWORDS |
The client can handle expired passwords. For more information, see Section 6.3.6, "Password Expiration and Sandbox Mode". This option was added in MySQL 5.6.10. |
CLIENT_COMPRESS |
Use compression protocol. |
CLIENT_FOUND_ROWS |
Return the number of found (matched) rows, not the number of changed rows. |
CLIENT_IGNORE_SIGPIPE |
Prevents the client library from installing a SIGPIPE
signal handler. This can be used to avoid conflicts with a handler that the application
has already installed.
|
CLIENT_IGNORE_SPACE |
Permit spaces after function names. Makes all functions names reserved words. |
CLIENT_INTERACTIVE |
Permit interactive_timeout seconds (instead of wait_timeout seconds) of inactivity before closing the
connection. The client's session wait_timeout variable is set to the value of the
session interactive_timeout variable.
|
CLIENT_LOCAL_FILES |
Enable LOAD DATA
LOCAL handling.
|
CLIENT_MULTI_RESULTS |
Tell the server that the client can handle multiple result sets from multiple-statement
executions or stored procedures. This flag is automatically enabled if CLIENT_MULTI_STATEMENTS is enabled. See the note
following this table for more information about this flag.
|
CLIENT_MULTI_STATEMENTS |
Tell the server that the client may send multiple statements in a single string
(separated by ";"). If this flag is not set,
multiple-statement execution is disabled. See the note following this table for more
information about this flag.
|
CLIENT_NO_SCHEMA |
Do not permit the db_name.tbl_name.col_name
syntax. This is for ODBC. It causes the parser to generate an error if you use that
syntax, which is useful for trapping bugs in some ODBC programs.
|
CLIENT_ODBC |
Unused. |
CLIENT_SSL |
Use SSL (encrypted protocol). Do not set this option within an application program; it
is set internally in the client library. Instead, use mysql_ssl_set() before calling mysql_real_connect().
|
CLIENT_REMEMBER_OPTIONS |
Remember options specified by calls to mysql_options(). Without this option, if mysql_real_connect() fails, you must repeat the mysql_options()
calls before trying to connect again. With this option, the mysql_options()calls need not be repeated.
|
If your program uses CALL statements to execute stored procedures, the CLIENT_MULTI_RESULTS
flag must be enabled. This is because each CALL
returns a result to indicate the call status, in addition to any result sets that might be returned by
statements executed within the procedure. Because CALL can return multiple results, process them using a loop that calls mysql_next_result() to determine whether there are more results.
CLIENT_MULTI_RESULTS can be enabled when you call mysql_real_connect(), either explicitly by passing the CLIENT_MULTI_RESULTS
flag itself, or implicitly by passing CLIENT_MULTI_STATEMENTS (which also enables
CLIENT_MULTI_RESULTS). In MySQL 5.6, CLIENT_MULTI_RESULTS is enabled by default.
If you enable CLIENT_MULTI_STATEMENTS or CLIENT_MULTI_RESULTS, process the result for every call to mysql_query() or mysql_real_query()
by using a loop that calls mysql_next_result() to determine whether there are more results. For an
example, see Section 22.8.17, "C API Support
for Multiple Statement Execution".
For some parameters, it is possible to have the value taken from an option file rather than from an explicit
value in the mysql_real_connect()
call. To do this, call mysql_options()
with the MYSQL_READ_DEFAULT_FILE or MYSQL_READ_DEFAULT_GROUP option before calling mysql_real_connect(). Then, in the mysql_real_connect() call, specify the "no-value" value for each parameter to be read from an option file:
For host, specify a value of NULL
or the empty string ("").
For user, specify a value of NULL
or the empty string.
For passwd, specify a value of NULL.
(For the password, a value of the empty string in the mysql_real_connect() call cannot be overridden in an option file,
because the empty string indicates explicitly that the MySQL account must have an empty password.)
For db, specify a value of NULL or the empty string.
For port, specify a value of 0.
For unix_socket, specify a value of NULL.
If no value is found in an option file for a parameter, its default value is used as indicated in the descriptions given earlier in this section.
A MYSQL* connection handle if the connection was successful, NULL
if the connection was unsuccessful. For a successful connection, the return value is the same as the value of
the first parameter.
Failed to connect to the MySQL server.
Failed to connect to the local MySQL server.
Failed to create an IP socket.
Out of memory.
Failed to create a Unix socket.
Failed to find the IP address for the host name.
A protocol mismatch resulted from attempting to connect to a server with a client library that uses a different protocol version.
Failed to create a named pipe on Windows.
Failed to wait for a named pipe on Windows.
Failed to get a pipe handler on Windows.
If connect_timeout
> 0 and it took longer than connect_timeout seconds to connect to the server or if the server
died while executing the init-command.
The MYSQL connection handle is already connected.
MYSQL mysql;mysql_init(&mysql);mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"your_prog_name");if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0)){ fprintf(stderr, "Failed to connect to database: Error: %s\n", mysql_error(&mysql));}
By using mysql_options() the MySQL library reads the [client]
and [your_prog_name] sections in the my.cnf file
which ensures that your program works, even if someone has set up MySQL in some nonstandard way.
Note that upon connection, mysql_real_connect() sets the reconnect flag (part
of the MYSQL structure) to a value of 1 in versions of
the API older than 5.0.3, or 0 in newer versions. A value of 1
for this flag indicates that if a statement cannot be performed because of a lost connection, to try
reconnecting to the server before giving up. You can use the MYSQL_OPT_RECONNECT
option to mysql_options() to control reconnection behavior.