int mysql_options(MYSQL *mysql, enum mysql_option
option, const void *arg)
Description
Can be used to set extra connect options and affect behavior for a connection. This function may be called multiple times to set several options.
mysql_options()
should be called
after mysql_init()
and before
mysql_connect()
or
mysql_real_connect()
.
The option
argument is the option that you
want to set; the arg
argument is the value
for the option. If the option is an integer,
arg
should point to the value of the integer.
The following list describes the possible options, their effect,
and how arg
is used for each option. Several
of the options apply only when the application is linked against
the libmysqld
embedded server library and are
unused for applications linked against the
libmysql
client library. For option
descriptions that indicate arg
is unused, its
value is irrelevant; it is conventional to pass 0.
MYSQL_INIT_COMMAND
(argument type:
char *
)
SQL statement to execute when connecting to the MySQL server. Automatically re-executed if reconnection occurs.
MYSQL_OPT_COMPRESS
(argument: not used)
Use the compressed client/server protocol.
MYSQL_OPT_CONNECT_TIMEOUT
(argument type:
unsigned int *
)
Connect timeout in seconds.
MYSQL_OPT_GUESS_CONNECTION
(argument: not
used)
For an application linked against the
libmysqld
embedded server library, this
allows the library to guess whether to use the embedded
server or a remote server. “Guess” means that
if the host name is set and is not
localhost
, it uses a remote server. This
behavior is the default.
MYSQL_OPT_USE_EMBEDDED_CONNECTION
and
MYSQL_OPT_USE_REMOTE_CONNECTION
can be
used to override it. This option is ignored for applications
linked against the libmysqlclient
client
library.
MYSQL_OPT_LOCAL_INFILE
(argument type:
optional pointer to unsigned int
)
If no pointer is given or if pointer points to an
unsigned int
that has a nonzero value,
the LOAD LOCAL INFILE
statement is
enabled.
MYSQL_OPT_NAMED_PIPE
(argument: not used)
Use named pipes to connect to a MySQL server on Windows, if the server allows named-pipe connections.
MYSQL_OPT_PROTOCOL
(argument type:
unsigned int *
)
Type of protocol to use. Should be one of the enum values of
mysql_protocol_type
defined in
mysql.h
.
MYSQL_OPT_READ_TIMEOUT
(argument type:
unsigned int *
)
The timeout in seconds for attempts to read from the server.
Each attempt uses this timeout value and there are retries
if necessary, so the total effective timeout value is three
times the option value. You can set the value so that a lost
connection can be detected earlier than the TCP/IP
Close_Wait_Timeout
value of 10 minutes.
This option works only for TCP/IP connections.
MYSQL_OPT_RECONNECT
(argument type:
my_bool *
)
Enable or disable automatic reconnection to the server if the connection is found to have been lost. Reconnect is off by default; this option provides a way to set reconnection behavior explicitly.
MYSQL_SET_CLIENT_IP
(argument type:
char *
)
For an application linked against the
libmysqld
embedded server library (when
libmysqld
is compiled with authentication
support), this means that the user is considered to have
connected from the specified IP address (specified as a
string) for authentication purposes. This option is ignored
for applications linked against the
libmysqlclient
client library.
MYSQL_OPT_SSL_VERIFY_SERVER_CERT
(argument type: my_bool *
)
Enable or disable verification of the server's Common Name value in its certificate against the host name used when connecting to the server. The connection is rejected if there is a mismatch. This feature can be used to prevent man-in-the-middle attacks. Verification is disabled by default.
MYSQL_OPT_USE_EMBEDDED_CONNECTION
(argument: not used)
For an application linked against the
libmysqld
embedded server library, this
forces the use of the embedded server for the connection.
This option is ignored for applications linked against the
libmysqlclient
client library.
MYSQL_OPT_USE_REMOTE_CONNECTION
(argument: not used)
For an application linked against the
libmysqld
embedded server library, this
forces the use of a remote server for the connection. This
option is ignored for applications linked against the
libmysqlclient
client library.
MYSQL_OPT_USE_RESULT
(argument: not used)
This option is unused.
MYSQL_OPT_WRITE_TIMEOUT
(argument type:
unsigned int *
)
The timeout in seconds for attempts to write to the server.
Each attempt uses this timeout value and there are
net_retry_count
retries if
necessary, so the total effective timeout value is
net_retry_count
times the
option value. This option works only for TCP/IP connections.
MYSQL_READ_DEFAULT_FILE
(argument type:
char *
)
Read options from the named option file instead of from
my.cnf
.
MYSQL_READ_DEFAULT_GROUP
(argument type:
char *
)
Read options from the named group from
my.cnf
or the file specified with
MYSQL_READ_DEFAULT_FILE
.
MYSQL_REPORT_DATA_TRUNCATION
(argument
type: my_bool *
)
Enable or disable reporting of data truncation errors for
prepared statements via the error
member
of MYSQL_BIND
structures. (Default:
enabled.)
MYSQL_SECURE_AUTH
(argument type:
my_bool *
)
Whether to connect to a server that does not support the password hashing used in MySQL 4.1.1 and later.
MYSQL_SET_CHARSET_DIR
(argument type:
char *
)
The path name to the directory that contains character set definition files.
MYSQL_SET_CHARSET_NAME
(argument type:
char *
)
The name of the character set to use as the default character set.
MYSQL_SHARED_MEMORY_BASE_NAME
(argument
type: char *
)
The name of the shared-memory object for communication to
the server on Windows, if the server supports shared-memory
connections. Should have the same value as the
--shared-memory-base-name
option used for the mysqld server you
want to connect to.
The client
group is always read if you use
MYSQL_READ_DEFAULT_FILE
or
MYSQL_READ_DEFAULT_GROUP
.
The specified group in the option file may contain the following options.
Option | Description |
character-sets-dir= |
The directory where character sets are installed. |
compress |
Use the compressed client/server protocol. |
connect-timeout= |
Connect timeout in seconds. On Linux this timeout is also used for waiting for the first answer from the server. |
database= |
Connect to this database if no database was specified in the connect command. |
debug |
Debug options. |
default-character-set= |
The default character set to use. |
disable-local-infile |
Disable use of LOAD DATA
LOCAL . |
host= |
Default host name. |
init-command= |
Statement to execute when connecting to MySQL server. Automatically re-executed if reconnection occurs. |
interactive-timeout= |
Same as specifying CLIENT_INTERACTIVE to
mysql_real_connect() .
See Section 20.9.3.52, “mysql_real_connect() ”. |
local-infile[={0|1}] |
If no argument or nonzero argument, enable use of
LOAD DATA
LOCAL ; otherwise disable. |
max_allowed_packet= |
Maximum size of packet that client can read from server. |
multi-queries , multi-results
|
Allow multiple result sets from multiple-statement executions or stored procedures. |
multi-statements |
Allow the client to send multiple statements in a single string
(separated by “; ”). |
password= |
Default password. |
pipe |
Use named pipes to connect to a MySQL server on Windows. |
port= |
Default port number. |
protocol={TCP|SOCKET|PIPE|MEMORY} |
The protocol to use when connecting to the server. |
return-found-rows |
Tell mysql_info() to return found rows
instead of updated rows when using
UPDATE . |
shared-memory-base-name= |
Shared-memory name to use to connect to server. |
socket= |
Default socket file. |
ssl-ca= |
Certificate Authority file. |
ssl-capath= |
Certificate Authority directory. |
ssl-cert= |
Certificate file. |
ssl-cipher= |
Allowable SSL ciphers. |
ssl-key= |
Key file. |
timeout= |
Like connect-timeout . |
user |
Default user. |
timeout
has been replaced by
connect-timeout
, but
timeout
is still supported in MySQL
5.4 for backward compatibility.
For more information about option files, see Section 4.2.3.3, “Using Option Files”.
Return Values
Zero for success. Nonzero if you specify an unknown option.
Example
The following mysql_options()
calls request the use of compression in the client/server
protocol, cause options to be read from the
[odbc]
group of option files, and disable
transaction autocommit mode:
MYSQL mysql; mysql_init(&mysql); mysql_options(&mysql,MYSQL_OPT_COMPRESS,0); mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"odbc"); mysql_options(&mysql,MYSQL_INIT_COMMAND,"SET autocommit=0"); 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)); }
This code requests that the client use the compressed
client/server protocol and read the additional options from the
odbc
section in the
my.cnf
file.
User Comments
When retrying a connection, I used mysql_options() to set a connection timeout then called mysql_real_connect in a while loop:
mysql_options(...);
while(!mysql_real_connect(...))
{
nanosleep(...);
}
Doing this, it appears that the connection timeout was lost after the first iteration. I had to re-set the connection timeout after every attempt:
mysql_options(...);
while(!mysql_real_connect(...))
{
nanosleep(...);
mysql_options(...);
}
Don't know if this is the case for other options....
Set flag CLIENT_REMEMBER_OPTIONS in client_flag when you calling mysql_real_connect().
Without this flag, if mysql_real_connect() fails, you must repeat the mysql_options() calls before trying to connect again.
Speco
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