Oracle 5.0, Справочное руководство

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C API Function Descriptions
2164
In a nonmulti-threaded environment, the call to
mysql_library_init()
may be omitted, because
mysql_init()
will invoke it automatically as necessary. However,
mysql_library_init()
is
not thread-safe in a multi-threaded environment, and thus neither is
mysql_init()
, which calls
mysql_library_init()
. You must either call
mysql_library_init()
prior to spawning any
threads, or else use a mutex to protect the call, whether you invoke
mysql_library_init()
or
indirectly through
mysql_init()
. Do this prior to any other client library call.
The
argc
and
argv
arguments are analogous to the arguments to
main()
, and enable passing of
options to the embedded server. For convenience,
argc
may be
0
(zero) if there are no command-
line arguments for the server. This is the usual case for applications intended for use only as regular
(nonembedded) clients, and the call typically is written as
mysql_library_init(0, NULL, NULL)
.
#include <mysql.h>
#include <stdlib.h>
int main(void) {
if (mysql_library_init(0, NULL, NULL)) {
fprintf(stderr, "could not initialize MySQL library\n");
exit(1);
}
/* Use any MySQL API functions here */
mysql_library_end();
return EXIT_SUCCESS;
}
When arguments are to be passed (
argc
is greater than
0
), the first element of
argv
is ignored (it
typically contains the program name).
mysql_library_init()
makes a copy of the arguments so it
is safe to destroy
argv
or
groups
after the call.
For embedded applications, if you want to connect to an external server without starting the embedded
server, you have to specify a negative value for
argc
.
The
groups
argument is an array of strings that indicate the groups in option files from which to
read options. See Section 4.2.3.3, “Using Option Files” . Make the final entry in the array
NULL
. For
convenience, if the
groups
argument itself is
NULL
, the
[server]
and
[embedded]
groups are used
by default.
#include <mysql.h>
#include <stdlib.h>
static char *server_args[] = {
"this_program", /* this string is not used */
"--datadir=.",
"--key_buffer_size=32M"
};
static char *server_groups[] = {
"embedded",
"server",
"this_program_SERVER",
(char *)NULL
};
int main(void) {
if (mysql_library_init(sizeof(server_args) / sizeof(char *),
server_args, server_groups)) {
fprintf(stderr, "could not initialize MySQL library\n");
exit(1);
}
/* Use any MySQL API functions here */
mysql_library_end();
return EXIT_SUCCESS;
}