I am writing some code in C which connects to MYSQL server. I am using Netbeans and new to this. I configured it as directed and installed MYSQL Connector C. I also installed CYGWIN GCC, G++, GDB, MAKE from cygwin site. I created a c project and in the properties-> build-> c compiler->Include directories, set the path of mysql connector (C:\Program Files\MySQL\Connector C 6.0.2\include). Now i write some code to interect with MYSQL server, on build some error occurs.
#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>
int main(int argc, char** argv) {
MYSQL *conn;
MYSQL_RES *res;
MYSQL_ROW row;
char *server = "localhost";
char *user = "root";
char *password = "aaaa"; /* set me first */
char *database = "mysql";
conn = mysql_init(NULL);
/* Connect to database */
if (!mysql_real_connect(conn, server,
user, password, database, 0, NULL, 0)) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}
/* send SQL query */
if (mysql_query(conn, "show tables")) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}
res = mysql_use_result(conn);
/* output table name */
printf("MySQL Tables in mysql database:\n");
while ((row = mysql_fetch_row(res)) != NULL)
printf("%s \n", row[0]);
/* close connection */
mysql_free_result(res);
mysql_close(conn);
return (EXIT_SUCCESS);
}
After build following error occurs:
build/Debug/Cygwin-Windows/main.o: In function `main':
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:26: undefined reference to `_mysql_init'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:28: undefined reference to `_mysql_real_connect'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:30: undefined reference to `_mysql_error'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:34: undefined reference to `_mysql_query'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:35: undefined reference to `_mysql_error'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:38: undefined reference to `_mysql_use_result'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:41: undefined reference to `_mysql_fetch_row'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:44: undefined reference to `_mysql_free_result'
/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2/main.c:45: undefined reference to `_mysql_close'
make[2]: Leaving directory `/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2'
make[1]: Leaving directory `/cygdrive/c/Documents and Settings/AEM/My Documents/NetBeansProjects/CppApplication_2'
collect2: ld returned 1 exit status
make[2]: *** [dist/Debug/Cygwin-Windows/cppapplication_2.exe] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
BUILD FAILED (exit value 2, total time: 1s)
I googled a lot but could not find anything to solve this issue. Need Help.
add -lmysql to link with the mysql library (valid for gcc). Or, if you use another Compiler, tell the Compiler
where the Libs are (add the Path)
to link the Library to the executable. This is something different, then adding the Path.
Related
I am trying to connect to mariadb database using c program. Initially it was showing error for #include <mysql.h> as no such file or directory.
But after including directory name, that problem is solved now, but it is showing another error.
Following is the code I was trying to run:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// #include "C:/Program Files/MariaDB 10.11/include/mysql/my_global.h"
#include "mysql/mysql.h"
int main (int argc, char* argv[])
{
// Initialize Connection
MYSQL *conn;
if (!(conn = mysql_init(0)))
{
fprintf(stderr, "unable to initialize connection struct\n");
exit(1);
}
// Connect to the database
if (!mysql_real_connect(
conn, // Connection
"mariadb.example.net", // Host
"db_user", // User account
"db_user_password", // User password
"test", // Default database
3306, // Port number
NULL, // Path to socket file
0 // Additional options
));
{
// Report the failed-connection error & close the handle
fprintf(stderr, "Error connecting to Server: %s\n", mysql_error(conn));
mysql_close(conn);
exit(1);
}
// Use the Connection
// ...
// Close the Connection
mysql_close(conn);
return 0;
}
I am getting following error in output:
PS C:\Dev\Win> gcc Db_con.c -o Db_con
C:\Users\hajos\AppData\Local\Temp\ccGZ2Rhz.o:Db_con.c:(.text+0x1e): undefined reference to `mysql_init#4'
C:\Users\hajos\AppData\Local\Temp\ccGZ2Rhz.o:Db_con.c:(.text+0xa1): undefined reference to `mysql_real_connect#32'
C:\Users\hajos\AppData\Local\Temp\ccGZ2Rhz.o:Db_con.c:(.text+0xaf): undefined reference to `mysql_error#4'
C:\Users\hajos\AppData\Local\Temp\ccGZ2Rhz.o:Db_con.c:(.text+0xd9): undefined reference to `mysql_close#4'
collect2.exe: error: ld returned 1 exit status
Can anyone explain what is the problem and how to solve it?
You have to link against the MariaDB Connector/C libraries.
From MariaDB Connector/C documentation:
Linking your application against MariaDB Connector/C
Windows
For static linking the library libmariadb.lib is required, for dynamic linking use libmariadb.dll. Using the MSI installer, these libraries can be found in the lib directory of your MariaDB Connector/C installation.
Unless you use the experimental plugin remote_io (which requires the curl library) there are no dependencies to other libraries than the Windows system libraries.
I'm running OS 11.1 Big Sur and updating an objective C program that uses the MySql C API (NOT the C Connector).
I CAN connect to local MySql server from the command line using
/usr/local/mysql/bin/mysql --user=root --password=aPassword
but when my software tries to connect through the C API using mysql_real_connect(mSQLPtr, theHost, theLogin, thePass, theDatabase, 0, NULL, 0); it fails with
Failed to connect to database: Error: Can't connect to local MySQL
server through socket '/tmp/mysql.sock' (1)
I've read heaps of posts to try and fix it e.g. stopping and starting the server, checking that /tmp/mysql.sock file does exist after starting the server (AND IT DOES EXIST), and adding a my.cnf to the /etc folder. It contains:
[mysqld]
socket=/tmp/mysql.sock
[client]
socket=/tmp/mysql.sock
Nothing has worked so far.
Can anyone offer any suggestions please.
Cheers
Jeff
#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>
static char *host = "localhost";
static char *user = "user";
static char *pass = "password";
static char *db = "mysql";
static char *socket = NULL;
unsigned int port = 3306;
unsigned int flags = 0;
/*
* brew install mysql-client
* export PATH=/usr/local/opt/mysql-client/bin:$PATH
* brew install mysql-connector-c++ (optional)
* gcc -o main $(mysql_config --cflags) main.c $(mysql_config --libs) -L/usr/local/opt/openssl/lib
*
* -L/usr/local/opt/openssl/lib is required if you get ld: library not found for -lssl error
*/
int main(int argc, char *argv[]) {
MYSQL *con = mysql_init(NULL);
if (!mysql_real_connect(con, host, user, pass, db, port, socket, flags)) {
fprintf(stderr, "Error %s (%d)", mysql_error(con), mysql_errno(con));
exit(1);
}
printf("Connected\n");
return EXIT_SUCCESS;
}
I have a mysql server 8.0.21 running on ubuntu 20.04, on this later i also have a VB win7 32bi guest.
I'm trying to connect to the Mysql server from guest using c api (specifically 6.1.11 connector as newer MySQL 8 installations no more support win7)
I'm running the following basic program:
int main(){
MYSQL *conn;
conn = mysql_init (NULL);
if(mysql_real_connect ( conn, "169.254.128.100", "myuser","mypass", "my_schema", 3306, NULL,0 )==NULL)
{
fprintf(stderr, "%s\n", mysql_error(conn));
}
mysql_close ( conn );
return 0;
}
I get the error: "SSL Connection Error: Unknown error number"
The thing is i can connect fine using the ODBC DSN
I also checked the server status & it requires no ssl ("not in use")
thanks
#include <stdio.h>
#include <stdlib.h>
#include <mysql.h>
static char *host = "localhost";
static char *user = "user";
static char *pass = "password";
static char *db = "mysql";
static char *socket = NULL;
unsigned int port = 3306;
unsigned int flags = 0;
/*
* brew install mysql-client
* export PATH=/usr/local/opt/mysql-client/bin:$PATH
* brew install mysql-connector-c++ (optional)
* gcc -o main $(mysql_config --cflags) main.c $(mysql_config --libs) -L/usr/local/opt/openssl/lib
*
* -L/usr/local/opt/openssl/lib is required if you get ld: library not found for -lssl error
*/
int main(int argc, char *argv[]) {
MYSQL *con = mysql_init(NULL);
if (!mysql_real_connect(con, host, user, pass, db, port, socket, flags)) {
fprintf(stderr, "Error %s (%d)", mysql_error(con), mysql_errno(con));
exit(1);
}
printf("Connected\n");
return EXIT_SUCCESS;
}
You need to do this:
int sslmode = 1;
mysql_options(&p->mysqlConn, MYSQL_OPT_SSL_MODE, &sslmode);
i want to connect C to mysql using the following code:
#include <C:\Program Files\MySQL\MySQL Connector C 6.0.2\include\my_global.h>
#include <C:\Program Files\MySQL\MySQL Connector C 6.0.2\include\mysql.h>
#include <stdio.h>
MYSQL *conn; /* pointer to connection handler */
int main ( int argc, char *argv[] )
{
conn = mysql_init ( NULL );
mysql_real_connect (
conn,"localhost","root","","operator", 3306, NULL,0 );
mysql_close ( conn );
return 0;
}
When i try to compile ,i get:
Error 3 error LNK2019: unresolved external symbol _mysql_real_connect#32 referenced in function _main C:\Users\kristel\Documents\Visual Studio 2010\Projects\database\database\database.obj database
Error 4 error LNK2019: unresolved external symbol _mysql_init#4 referenced in function _main C:\Users\kristel\Documents\Visual Studio 2010\Projects\database\database\database.obj database
It seems like something is missing but i dont know when.
I have added the mysqllib.lib like in the picture but still the problem is not resolved.
Just another question: Doing my searches,i have found something concerning cmake.Is there any relation between my error and cmake?
Thank you.
While you have included the mySQL header files in your code, you haven't included the mySQL library in your link options.
My C client program connects with MySQL server. I can connect, but the problem arises when I try to implement error detection codes. If I do the following (here I have intentionally put incorrect user name):
#include "mysql.h"
int main()
{
MYSQL* conn_ptr_db;
conn_ptr_db = mysql_init(NULL);
if(!conn_ptr_db)
{
perror("Error connecting to MySQL! ");
exit(0);
}
if(mysql_real_connect(conn_ptr_db,"localhost","rooti","root","mysql",0,NULL,0))
{
printf("Hurrah! we have connected to MySQL! ");
mysql_close(conn_ptr_db);
}
else
{
printf("Connection failed to MySQL! \n");
printf("Error code: %d %s %s\n",mysql_errno(conn_ptr_db),mysql_sqlstate(conn_ptr_db),mysql_error(conn_ptr_db));
}
//mysql_close(conn_ptr_db);
return 0;
}
Now the output to this program:
./db_access
Connection failed to MySQL!
Error code: 1045 28000 Access denied for user 'rooti'#'localhost' (using password: YES)
This is the correct output.
But if I do the following:
#include "mysql.h"
int main()
{
MYSQL* conn_ptr_db;
conn_ptr_db = mysql_init(NULL);
if(!conn_ptr_db)
{
perror("Error connecting to MySQL! ");
exit(0);
}
//CHANGES -------------
conn_ptr_db = mysql_real_connect(conn_ptr_db,"localhost","rooti","root","mysql",0,NULL,0);
if(conn_ptr_db)
{
printf("Hurrah! we have connected to MySQL! ");
mysql_close(conn_ptr_db);
}
else
{
printf("Connection failed to MySQL! \n");
printf("Error code: %d %s %s\n",mysql_errno(conn_ptr_db),mysql_sqlstate(conn_ptr_db),mysql_error(conn_ptr_db));
}
//mysql_close(conn_ptr_db);
return 0;
}
I get the following output:
./db_access
Connection failed to MySQL!
Error code: 0 08001
Here, the mysql_errno() and mysql_error() are not working. Why?
After the connection has failed conn_ptr_db is set to NULL. You then try and use this value as a paramter to a call to msql_errono(), in effect msql_errno(NULL). Hence the error code your getting.
Because in the second example you assign the result to conn_ptr_db.
You should not have done so.
From the documentation:
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.
In the case of an unsuccessful connection (which you have), you've replaced your conn_ptr_db object with NULL then attempt to do stuff with it (mysql_error).
The documentation for mysql_error doesn't explicitly say that a NULL parameter is disallowed, but it's clear that you won't get the error relating to the original, actual connection context that you overwrote.