An example of connecting to a MySQL database in C using a config text file

mysql-db-conf-example.c

#include <mysql.h>
#include <my_global.h>

// Note: TRUE and FALSE will always be defined by the MySQL headers
#define MYSQL_CONF_NUM 4
#define MYSQL_CONF_HOSTNAME 0
#define MYSQL_CONF_DATABASE 1
#define MYSQL_CONF_USERNAME 2
#define MYSQL_CONF_PASSWORD 3

/**
 * Load a MySQL config text file consisting of four separate lines:
 * - hostname
 * - database name
 * - username
 * - password
 *
 * assumes macros for TRUE = 1, FALSE = 0
 * returns (int) success
 */
int get_mysql_conf(char *conf[])
{
  // Load the config file
  FILE *fp = fopen("CONFIG_FILE_PATH_GOES_HERE", "r");
  if (!fp) {
    return FALSE;
  }

  // Read each required line, error if empty
  char buffer[1024];
  for (int i = 0; i < MYSQL_CONF_NUM; ++i) {
    if (fgets(buffer, sizeof(buffer), fp) == NULL) {
      return FALSE;
    }

    strtok(buffer, "\n");
    strtok(buffer, "\r");
    conf[i] = malloc(sizeof(char) * strlen(buffer) + 1);
    if (conf[i] == NULL) {
      return FALSE;
    }

    strcpy(conf[i], buffer);
  }

  fclose(fp);

  return TRUE;
}

// Open a database connection
printf("MySQL client version: %s\n", mysql_get_client_info());
MYSQL *conn = mysql_init(NULL);
if (conn == NULL) {
  printf("ERROR: Could not create database connection\n");
  return 1;
}

// Load the config file
char *conf[MYSQL_CONF_NUM];
if (!get_mysql_conf(conf)) {
  printf("ERROR: Could not load database configuration file\n");
  return 1;
}

// Connect to the target database
if (mysql_real_connect(conn, conf[MYSQL_CONF_HOSTNAME], conf[MYSQL_CONF_USERNAME], conf[MYSQL_CONF_PASSWORD], conf[MYSQL_CONF_DATABASE], 0, NULL, 0) == NULL) {
  printf("ERROR: Could not connect to the target database\n");
  return 1;
}