Question

I’m new to using the gwan server(link) and for that matter programming in c. I wanted to know what was the easiest way to use mysql in a c script for the gwan server?

I’ve experimented with dbi.c as used here and the project page can be found here, but also found that there is a c API for mysql itself which you can find here.

Anyone have experience using either or both? What are some of the pros/cons? Are there other libraries that make connecting to mysql easy for a noob like myself?

Any help appreciated.

Thanks!

[EDIT]
Also is libdbi thread safe? it appears to not be.

[EDIT 2]
It appears that the mysql lib itself is the easy way to go unless you think might be switching database types later as libdbi appears to be able to have different drivers which is nice for abstraction.

Relating to GWAN for me if i had any “mysql code” in the main function of a handler it appeared to be unsafe and caused random errors intermittently, but if i put the “mysql code” in the init function and put any data i need in a kv store accessed off of one of the global pointers the random errors went away completely. (I was using libdbi i assume it would be the same for the mysql api)

Hope this helps

Answer 1

I always prefer using the native c api…

#pragma link "/usr/lib/libmysqlclient.so"

#include "gwan.h"
#include <mysql/mysql.h>


int
main (int argc, char **argv)
{
  MYSQL_RES *result;
  MYSQL_ROW row;
  MYSQL conn, *conn_h;

  conn_h = mysql_init (&conn);
  if (!conn_h)
    {
      return 200;
    }

  if (!mysql_real_connect (conn_h, "localhost", ctx->usr, ctx->psw, NULL, 0, NULL, 0))
    {
      mysql_close (conn_h);
      return 200;
    }

  mysql_select_db (conn_h, "");

  char *query = "";

  if (mysql_query (conn_h, query))
    {
      mysql_close (conn_h);
      return 200;
    }

  result = mysql_store_result (conn_h);
  if (!result)
    {
      mysql_close (conn_h);
      return 200;
    }

  if (mysql_num_rows (result) == 0)
    {
      return 200;
    }

  while ((row = mysql_fetch_row (result)))
    {
      /* do something with row[i] */
    }

  mysql_free_result (result);
  mysql_close (conn_h);

  return 200;  // Ok
}

Keep in mind you need to initialize the mysql library if you plan to spawn threads (this code is not thread safe).

Hope this help you someway.