From my mailbag:
How do I write a C program to connect MySQL database server?
MySQL database does support C program API just like PHP or perl.
The C API code is distributed with MySQL. It is included in the mysqlclient library and allows C programs to access a database.
Many of the clients in the MySQL source distribution are written in C. If you are looking for examples that demonstrate how to use the C API, take a look at these clients. You can find these in the clients directory in the MySQL source distribution.
Requirements
Make sure you have development environment installed such as gcc, mysql development package etc. Following is the list summarize the list of packages to compile program:
- mysql: MySQL client programs and shared library
- mysqlclient: Backlevel MySQL shared libraries (old libs)
- mysql-devel: Files for development of MySQL applications (a must have)
- mysql-server: Mysql server itself
- gcc, make and other development libs: GNU C compiler
Sample C Program
Following instructions should work on any Linux distro or UNIX computer. Here is the small program that connects to mysql server and list tables from mysql database.(download link):
/* Simple C program that connects to MySQL Database server*/
#include <mysql.h>
#include <stdio.h>
main() {
MYSQL *conn;
MYSQL_RES *res;
MYSQL_ROW row;
char *server = "localhost";
char *user = "root";
char *password = "PASSWORD"; /* 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);
}
How do I compile and link program against MySQL libs?
MySQL comes with a special script called mysql_config. It provides you with useful information for compiling your MySQL client and connecting it to MySQL database server. You need to use following two options.
Pass --libs option - Libraries and options required to link with the MySQL client library.
$ mysql_config --libs
Output:
-L/usr/lib64/mysql -lmysqlclient -lz -lcrypt -lnsl -lm -L/usr/lib64 -lssl -lcrypto
Pass --cflags option - Compiler flags to find include files and critical compiler flags and defines used when compiling the libmysqlclient library.$ mysql_config --cflags
Output:
-I/usr/include/mysql -g -pipe -m64 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing
You need to pass above option to GNU C compiler i.e. gcc. So to compile above program, enter:$ gcc -o output-file $(mysql_config --cflags) mysql-c-api.c $(mysql_config --libs)
Now execute program:$ ./output-file
Output:
MySQL Tables in mysql database: columns_priv db func help_category help_keyword help_relation help_topic host tables_priv time_zone time_zone_leap_second time_zone_name time_zone_transition time_zone_transition_type user